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Are zap stoppers really needed on alternators?
Are zap stoppers really needed on alternators? These aftermkt devices claim to
portect alt. diodes against damage from transients. I can't imagine that engineers at places like Motorola would design alternators that needed external aftermarket devices to effectively protect them from transients. I have never blown up an alternator from switching it in and out of a load, although people say this is often fatal to the diodes. I have run alternators open circuit (no load at all) with no problems. Was I just lucky? |
Are zap stoppers really needed on alternators?
"BOEING377" wrote in message ... Are zap stoppers really needed on alternators? These aftermkt devices claim to portect alt. diodes against damage from transients. I can't imagine that engineers at places like Motorola would design alternators that needed external aftermarket devices to effectively protect them from transients. I have never blown up an alternator from switching it in and out of a load, although people say this is often fatal to the diodes. I have run alternators open circuit (no load at all) with no problems. Was I just lucky? The fault conditions of a vehicle electrical system are very well known. Good engineering practice dictates that the item you design should withstand all normal operating conditions, plus those conditions generated by a single fault, or even multiple faults. How long your device survives, and how many multiple fault conditions it will tolerate, is controlled by economics. Running the engine while the battery lead is disconnected is certainly a single-fault (and reasonably likely to occur) condition. I know I have done this rather often, and I have never had any associated failures. OTOH, it has always been done with GM autos with internal regulator alternators. So, however they do it, the GM engineers have designed-in a control over that single-fault condition. Notice that I said a "control" and not a "tolerance". In the "no battery" single-fault condition, the alternator will supply the vehicle electric power load. If the loss of the battery allows for the alternator to create a vastly over-voltage condition, then protection would have to be designed into every electrical load device. It's a lot easier to just control the alternator output voltage. From my experience, the alternator is one of the most reliable parts of your car. Almost everything wears out or needs service before the alternator. If your alternator fails, I think you must be exceptionally unlucky, or very creative in producing a really unusual fault condition. Ed |
Are zap stoppers really needed on alternators?
For what they cost, they're good insurance. At least, if you think somebody
will turn the battery switch off while the engine is running. -- Keith __ Why is it that if you tell someone there are 6.3 trillion stars in the universe they will believe it, but if you tell them that your teak has wet varnish they have to touch it? "BOEING377" wrote in message ... Are zap stoppers really needed on alternators? These aftermkt devices claim to portect alt. diodes against damage from transients. I can't imagine that engineers at places like Motorola would design alternators that needed external aftermarket devices to effectively protect them from transients. I have never blown up an alternator from switching it in and out of a load, although people say this is often fatal to the diodes. I have run alternators open circuit (no load at all) with no problems. Was I just lucky? |
Are zap stoppers really needed on alternators?
What does fry diodes is breaking the
output circuit WHILE the alternator is producing current I think that's what the poster said: """""For what they cost, they're good insurance. At least, if you think somebody will turn the battery switch off while the engine is running."""""""""" S/V Express 30 "Ringmaster" Trains are a winter sport |
Are zap stoppers really needed on alternators?
SAIL LOCO wrote: What does fry diodes is breaking the output circuit WHILE the alternator is producing current I think that's what the poster said: I didn't read it that way. HE said "running the engine while the battery is disconnected." I am talking about disconecting the battery while the engine is running. BIG difference. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Are zap stoppers really needed on alternators?
If he's "running the engine while the battery is disconnected," but he
didn't disconnect while it was running, I'm wondering how he got it started. "Glenn Ashmore" wrote in message ... SAIL LOCO wrote: What does fry diodes is breaking the output circuit WHILE the alternator is producing current I think that's what the poster said: I didn't read it that way. HE said "running the engine while the battery is disconnected." I am talking about disconecting the battery while the engine is running. BIG difference. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Are zap stoppers really needed on alternators?
You can disconnect the battery while the engine is running and cause
no damage to the alternator, provided the alternator is not putting out much current. (battery fully charged, no accessories drawing current) If the alternator is supplying much current then you will probably zap the diodes in it. The voltage regulator monitors the alternators output voltage and changes the field voltage on the alternator to control the output. The problem is, being that a magnetic field is involved it does not change instantly. There is a time lag for the field to collapse and reduce the alternators output. When the load is suddenly disconnected from the alternator, when there is a substantial load on it, there is a large voltage generated in the alternators windings from the collapsing winding magnetic field. (the magnetic field collapses because there is no more load on it) That is connected to the diodes. The voltage regulator sees the large voltage spike and tells the field winding to shut down the field current but it is too late as there is no way to stop the magnetic field in the alternator windings from collapsing. The regulator can stop the field from building up before the alternator output current goes up but once it is there, the magnetic field has to first collapse to stop further output. When the alternator is putting out a large current the alternators windings have a high magnetic field in them. Disconnecting the alternators load causes the magnetic fields to suddenly collapse and generate a large voltage with nothing to limit the voltage. (no battery to absorb it) Note: A changing magnetic field is what generates voltage in the windings. This happened normally when the alternator is supplying power as wanted. The uncontrolled change is what causes the damage. Regards Gary On Sun, 13 Jul 2003 02:17:15 GMT, "johnh" wrote: If he's "running the engine while the battery is disconnected," but he didn't disconnect while it was running, I'm wondering how he got it started. "Glenn Ashmore" wrote in message ... SAIL LOCO wrote: What does fry diodes is breaking the output circuit WHILE the alternator is producing current I think that's what the poster said: I didn't read it that way. HE said "running the engine while the battery is disconnected." I am talking about disconecting the battery while the engine is running. BIG difference. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Are zap stoppers really needed on alternators?
Jumpre cables :-) Actually it takes a second or two to get the
alternator up to full current. The main thing is that once the regulator starts putting out a significant current and the circuit is broken, the regulator can't drop the field current fast enough to protect the diodes. With a starter battery, the alternator is usually only topping off the battery for what was needed to start the engine which only takes a few minutes. After that the load is just the other devices on the system and disconnecting the battery makes little difference. An alternator recharging a house battery bank could be putting out many amps for an hour or more. This is one of the major differences between a normal automotive alternator and a true "marine" (read EMT, utility or industrial) alternator. In comparison an automotive alternator has it real easy. Also, the voltage is directly related to the number of flux lines broken by the coil wires. When the field current stops the magnetic field collapses and then the number of flux lines broken is the combination of the coil rotation and the collapsing field. The result can be a spike. johnh wrote: If he's "running the engine while the battery is disconnected," but he didn't disconnect while it was running, I'm wondering how he got it started. "Glenn Ashmore" wrote in message ... SAIL LOCO wrote: What does fry diodes is breaking the output circuit WHILE the alternator is producing current I think that's what the poster said: I didn't read it that way. HE said "running the engine while the battery is disconnected." I am talking about disconecting the battery while the engine is running. BIG difference. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Are zap stoppers really needed on alternators?
Ed Price wrote: So I looked at the Xantrex site, trying to get some idea of a Zap-stop's performance. I couldn't find a circuit diagram for how the Zap-stop is hooked up to the alternator. Xantrex says something about connection across the rectifiers, but that isn't clear enough for me. Also, Xantrex doesn't say anything about how fast the Zap-stop begins to conduct when presented with a voltage excursion. Does Xantrex have some hard data on their product, or do they just expect you to trust them? The Zap Stop connects between the alternator output and ground. It is just a high voltage diode with a reverse breakdown voltage a bit higher than the operating voltage of the alternator. When the voltage exceeds this level the diode starts to conduct instantly shorting it to ground. The alternator diodes are designed for high amperage at relatively low voltages. The Zap Stop diode is designed for high voltages but will only handle high amperage for the few milliseconds it takes for the regulator to regain control. I don't think it could stand up to something like a loose sense wire on a high amperage alternator where the voltage and amp output stays high for any length of time. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Are zap stoppers really needed on alternators?
Since we are on the topic does anyone know for sure if the ZapStop can be used
with the Hitachi alternators with the built in regulators found on most Yanmar engines? Thanks. S/V Express 30 "Ringmaster" Trains are a winter sport |
Are zap stoppers really needed on alternators?
"Glenn Ashmore" wrote in message ... Ed Price wrote: So I looked at the Xantrex site, trying to get some idea of a Zap-stop's performance. I couldn't find a circuit diagram for how the Zap-stop is hooked up to the alternator. Xantrex says something about connection across the rectifiers, but that isn't clear enough for me. Also, Xantrex doesn't say anything about how fast the Zap-stop begins to conduct when presented with a voltage excursion. Does Xantrex have some hard data on their product, or do they just expect you to trust them? The Zap Stop connects between the alternator output and ground. It is just a high voltage diode with a reverse breakdown voltage a bit higher than the operating voltage of the alternator. When the voltage exceeds this level the diode starts to conduct instantly shorting it to ground. The alternator diodes are designed for high amperage at relatively low voltages. The Zap Stop diode is designed for high voltages but will only handle high amperage for the few milliseconds it takes for the regulator to regain control. I don't think it could stand up to something like a loose sense wire on a high amperage alternator where the voltage and amp output stays high for any length of time. -- Glenn Ashmore If the Zap-stop is connected to the alternator output, then it is positioned best to protect the alternator against transients originating in the rest of the vehicle's electrical system. (The worst source might be a high-current motor, like the AC blower fan.) OTOH, earlier posts have said that the sudden removal of load causes a high voltage transient in the alternator's windings. This means that the Zap-stop protects the alternator diodes from a high voltage by requiring the diodes to pass a massive current transient into the Zap-stop and to ground. That's strange protection! If you wanted to protect against an alternator winding over-voltage, wouldn't you have to put the protection at the winding side of the alternator diodes? The last time I looked inside an alternator, it had three field windings connected to a 6-diode full-wave bridge rectifier. Protecting the bridge against voltage transients would require one Zap-stop type device across each winding. An over-voltage event would then conduct through the Zap-stop devices, and not through the alternator diodes. Could all of this discussion have been based on a misconception of what happens when a heavy load current (into an inductive load like a motor winding). The potentially damaging transient is caused by the counter emf from the load, and not from any "slow regulator" effect within the alternator. If the Zap-stop is mounted to the alternator output lug, then that's apparently what the Zap-stop is configured to protect against. Ed |
Are zap stoppers really needed on alternators?
I believe we may be looking at it wrong. Go back to the original
problem. When the high amperage going to the battery is interupted, the voltage starts to rise. What the Zap Stop does is provide an alternate path for the current so that the flow is not interupted. Yes, the coils are still outputting through the rectifier but if we can detect the start of this rise fast enough and redirect the rectifier output to ground, the current flow never stops so the voltage never gets high enough to damage the rectifier. BTW, in the other thread you were asking about a schematic. Here it is: + --------|------ - It is just a zenier diode (or maybe several in parallel) in a nice box wired against the normal current flow. When the voltage rises above the breakdown rating of the diode, it conducts. As usual with most "marine" devices, it is 5% material and 95% marketing but it does the job. Ed Price wrote: If the Zap-stop is connected to the alternator output, then it is positioned best to protect the alternator against transients originating in the rest of the vehicle's electrical system. (The worst source might be a high-current motor, like the AC blower fan.) OTOH, earlier posts have said that the sudden removal of load causes a high voltage transient in the alternator's windings. This means that the Zap-stop protects the alternator diodes from a high voltage by requiring the diodes to pass a massive current transient into the Zap-stop and to ground. That's strange protection! If you wanted to protect against an alternator winding over-voltage, wouldn't you have to put the protection at the winding side of the alternator diodes? The last time I looked inside an alternator, it had three field windings connected to a 6-diode full-wave bridge rectifier. Protecting the bridge against voltage transients would require one Zap-stop type device across each winding. An over-voltage event would then conduct through the Zap-stop devices, and not through the alternator diodes. Could all of this discussion have been based on a misconception of what happens when a heavy load current (into an inductive load like a motor winding). The potentially damaging transient is caused by the counter emf from the load, and not from any "slow regulator" effect within the alternator. If the Zap-stop is mounted to the alternator output lug, then that's apparently what the Zap-stop is configured to protect against. Ed -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Are zap stoppers really needed on alternators?
OK, so the Zap-stop is wired across the output of the alternator, and it's
just a zener diode. Now, how can a diode be damaged? One way is to exceed its reverse voltage capability. Another way is to exceed its current capacity. Put the Zap-stop as described, and apply the transient from the vehicle side. Either a high-voltage positive or negative transient will result in strong conduction through the zener. As long as the zener can sink it, the voltage will be limited by the strong conduction. But now, posit that the overvoltage transient is starting in the alternator windings. The zap-stop, on the output side of the bridge, may go into strong conduction. But that current will also have to flow through the bridge diodes. So how does causing a massive current through the alternator diodes provide protection? Ed "Glenn Ashmore" wrote in message ... I believe we may be looking at it wrong. Go back to the original problem. When the high amperage going to the battery is interupted, the voltage starts to rise. What the Zap Stop does is provide an alternate path for the current so that the flow is not interupted. Yes, the coils are still outputting through the rectifier but if we can detect the start of this rise fast enough and redirect the rectifier output to ground, the current flow never stops so the voltage never gets high enough to damage the rectifier. BTW, in the other thread you were asking about a schematic. Here it is: + --------|------ - It is just a zenier diode (or maybe several in parallel) in a nice box wired against the normal current flow. When the voltage rises above the breakdown rating of the diode, it conducts. As usual with most "marine" devices, it is 5% material and 95% marketing but it does the job. Ed Price wrote: If the Zap-stop is connected to the alternator output, then it is positioned best to protect the alternator against transients originating in the rest of the vehicle's electrical system. (The worst source might be a high-current motor, like the AC blower fan.) OTOH, earlier posts have said that the sudden removal of load causes a high voltage transient in the alternator's windings. This means that the Zap-stop protects the alternator diodes from a high voltage by requiring the diodes to pass a massive current transient into the Zap-stop and to ground. That's strange protection! If you wanted to protect against an alternator winding over-voltage, wouldn't you have to put the protection at the winding side of the alternator diodes? The last time I looked inside an alternator, it had three field windings connected to a 6-diode full-wave bridge rectifier. Protecting the bridge against voltage transients would require one Zap-stop type device across each winding. An over-voltage event would then conduct through the Zap-stop devices, and not through the alternator diodes. Could all of this discussion have been based on a misconception of what happens when a heavy load current (into an inductive load like a motor winding). The potentially damaging transient is caused by the counter emf from the load, and not from any "slow regulator" effect within the alternator. If the Zap-stop is mounted to the alternator output lug, then that's apparently what the Zap-stop is configured to protect against. Ed -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Are zap stoppers really needed on alternators?
Ed Price wrote:
.... So how does causing a massive current through the alternator diodes provide protection? By limiting voltage. Diodes can tolerate massive current for short (milli or microsecond) periods of time without damage from overheating, but excess voltage spikes of the same duration may "zap" the crystal matricies that make them work as diodes. |
Are zap stoppers really needed on alternators?
"Vito" wrote in message ... Ed Price wrote: .... So how does causing a massive current through the alternator diodes provide protection? By limiting voltage. Diodes can tolerate massive current for short (milli or microsecond) periods of time without damage from overheating, but excess voltage spikes of the same duration may "zap" the crystal matricies that make them work as diodes. In the long history of alternator existence, Xentrex has been the only one to notice that alternators need a transient suppressor on their output terminal? Another poster contends that the alternator experiences several hundred milliseconds of overvoltage before its regulation can adjust to a load cut-off. A couple of hundred milliseconds dumping a hundred amps or so into the short-circuit that the Zap-stop presents is bad news for alternator diodes. Please address my initial comment; why does Xentrex put the "protection" on the wrong (my assertion) side of the alternator diodes? Ed |
Are zap stoppers really needed on alternators?
"Glenn Ashmore" wrote in message ... First of all, teh Zap Stop is not intended to protect anything from external spikes. There are very few situations on a boat that will cause a damaging spike back into the alternator other than a lightning strike and in that case all bets are off. The Zap Stop is only intended to protect the alternator from self destructing from a load dump. It does nothing else. It does this by clamping the voltage lower than the damaging point for the rectifier. In a load dump the voltage spike is what fries the rectifier diodes not the amperage. And how do you "clamp" a voltage when a voltage source is trying to drive it higher? As the Zap-stop does, by presenting a conductive path that has a very low resistance. The current is limited only by the source's internal resistance. I have no idea what the internal resistance of a large alternator is, but I would guess maybe 0.01 ohms. The important point is that you have to be able to sink a lot of current during the alternator's field winding voltage excursion. Putting the protective device on the load side of the alternator diodes is a solution that requires a heavy current draw through the alternator diodes during a protective event. For illustration, lets say we have a big honkin' 250 amp Balmar cranking out full power 15 volts into the house bank (3,750 watts) when somebody turns the master switch and the output voltage starts to rise. The regulator is still supplying the same current to the field and the RPM has not changed. As no additional energy is being supplied to the alternator the total power output remains the same. Absolutely bogus assumption about power output remaining constant. I am assuming that your alternator has an electronic, not a mechanical, regulation scheme. Are you claiming that the regulation can track load variations during normal operation, but, if the load is suddenly shed, it takes hundreds of milliseconds to react?! Power is volts * amps so as the voltage rises the amperage has to drop. For that 200-300 milliseconds that it takes for the regulator to adjust the field current the zenier has to absorb that 3,750 watts of excess power. Diodes that can handle this amount of power for that length of time are not hard to find. Digikey sells them for about a buck apiece. I checked my Digikey catalog, but can't find any "zenier" diodes. Perhaps you could fix your spull chucker; your consistent use of the wrong spelling is beginning to bug me, as real experts know the names of their tools. You know, you pound nails with a hammer, and discussing nail technology is disconcerting when the other guy keeps talking about his hummer. But regardless of how much diodes cost, where you buy them, and whether they will fail trying to carry x kiloamps for y milliseconds, the initial point I asked was why it was good practice to put the protection on the load side of the alternator diodes. Telling me that you can get away with it is not a good answer. Ed |
Are zap stoppers really needed on alternators?
Glenn Ashmore has accurately described the problem - load
dump. Depending on standard, load dump on 12 volts can be 60 volts or as high as 270 volts. Two standards are SAE J1455 and ISO 7637-1. As Glenn has accurately described, load dump can be created by disconnecting a major load from alternator - such as battery. Another has too much experience without underlying theory. His proof that something does not exist is that he disconnected a battery and failure did not occur. Reasoning equivalent to walking with only one leg which is why his response is: Absolutely bogus assumption about power output remaining constant. That leg called underlying theory is essential to understanding how things really work. Load dump means automotive type electronics must be designed beyond just the 12 volt power. SGS Thompson defines load dump as: - Peak voltage 80 to 100 volts - Duration 300 to 400 milliseconds - Series resistance 0.2 to 1 ohms" Even laptop power supplies for mobile power cost more money because load dump protection is required. SG Thompson makes load dump protection circuits such as LDP24 or RBO series. But they admit: The protection at the alternator level is a quite new concept and all the technical problems do not seem to be completely solved. Yes, you were lucky in not damaging the alternator if disconnecting when alternator was outputting power. BOEING377 wrote: Are zap stoppers really needed on alternators? These aftermkt devices claim to portect alt. diodes against damage from transients. I can't imagine that engineers at places like Motorola would design alternators that needed external aftermarket devices to effectively protect them from transients. I have never blown up an alternator from switching it in and out of a load, although people say this is often fatal to the diodes. I have run alternators open circuit (no load at all) with no problems. Was I just lucky? |
Are zap stoppers really needed on alternators?
Thanks. I gave up.
There are none so blind as those who will not see. w_tom wrote: Glenn Ashmore has accurately described the problem - load dump. Depending on standard, load dump on 12 volts can be 60 volts or as high as 270 volts. Two standards are SAE J1455 and ISO 7637-1. As Glenn has accurately described, load dump can be created by disconnecting a major load from alternator - such as battery. Another has too much experience without underlying theory. His proof that something does not exist is that he disconnected a battery and failure did not occur. Reasoning equivalent to walking with only one leg which is why his response is: Absolutely bogus assumption about power output remaining constant. That leg called underlying theory is essential to understanding how things really work. Load dump means automotive type electronics must be designed beyond just the 12 volt power. SGS Thompson defines load dump as: - Peak voltage 80 to 100 volts - Duration 300 to 400 milliseconds - Series resistance 0.2 to 1 ohms" Even laptop power supplies for mobile power cost more money because load dump protection is required. SG Thompson makes load dump protection circuits such as LDP24 or RBO series. But they admit: The protection at the alternator level is a quite new concept and all the technical problems do not seem to be completely solved. Yes, you were lucky in not damaging the alternator if disconnecting when alternator was outputting power. BOEING377 wrote: Are zap stoppers really needed on alternators? These aftermkt devices claim to portect alt. diodes against damage from transients. I can't imagine that engineers at places like Motorola would design alternators that needed external aftermarket devices to effectively protect them from transients. I have never blown up an alternator from switching it in and out of a load, although people say this is often fatal to the diodes. I have run alternators open circuit (no load at all) with no problems. Was I just lucky? -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Are zap stoppers really needed on alternators?
because it is easy? or maybe you are trolling....
"Ed Price" wrote in message news:Zp9Ra.613$Ye.496@fed1read02... "Glenn Ashmore" wrote in message ... First of all, teh Zap Stop is not intended to protect anything from external spikes. There are very few situations on a boat that will cause a damaging spike back into the alternator other than a lightning strike and in that case all bets are off. The Zap Stop is only intended to protect the alternator from self destructing from a load dump. It does nothing else. It does this by clamping the voltage lower than the damaging point for the rectifier. In a load dump the voltage spike is what fries the rectifier diodes not the amperage. And how do you "clamp" a voltage when a voltage source is trying to drive it higher? As the Zap-stop does, by presenting a conductive path that has a very low resistance. The current is limited only by the source's internal resistance. I have no idea what the internal resistance of a large alternator is, but I would guess maybe 0.01 ohms. The important point is that you have to be able to sink a lot of current during the alternator's field winding voltage excursion. Putting the protective device on the load side of the alternator diodes is a solution that requires a heavy current draw through the alternator diodes during a protective event. For illustration, lets say we have a big honkin' 250 amp Balmar cranking out full power 15 volts into the house bank (3,750 watts) when somebody turns the master switch and the output voltage starts to rise. The regulator is still supplying the same current to the field and the RPM has not changed. As no additional energy is being supplied to the alternator the total power output remains the same. Absolutely bogus assumption about power output remaining constant. I am assuming that your alternator has an electronic, not a mechanical, regulation scheme. Are you claiming that the regulation can track load variations during normal operation, but, if the load is suddenly shed, it takes hundreds of milliseconds to react?! Power is volts * amps so as the voltage rises the amperage has to drop. For that 200-300 milliseconds that it takes for the regulator to adjust the field current the zenier has to absorb that 3,750 watts of excess power. Diodes that can handle this amount of power for that length of time are not hard to find. Digikey sells them for about a buck apiece. I checked my Digikey catalog, but can't find any "zenier" diodes. Perhaps you could fix your spull chucker; your consistent use of the wrong spelling is beginning to bug me, as real experts know the names of their tools. You know, you pound nails with a hammer, and discussing nail technology is disconcerting when the other guy keeps talking about his hummer. But regardless of how much diodes cost, where you buy them, and whether they will fail trying to carry x kiloamps for y milliseconds, the initial point I asked was why it was good practice to put the protection on the load side of the alternator diodes. Telling me that you can get away with it is not a good answer. Ed |
Are zap stoppers really needed on alternators?
"Glenn Ashmore" wrote in message ... Thanks. I gave up. There are none so blind as those who will not see. w_tom wrote: Glenn Ashmore has accurately described the problem - load dump. Depending on standard, load dump on 12 volts can be 60 volts or as high as 270 volts. Two standards are SAE J1455 and ISO 7637-1. As Glenn has accurately described, load dump can be created by disconnecting a major load from alternator - such as battery. Well, pardon me for asking you to address my question. In case you didn't remember, since it always seems to slip your attention during your posts, I wanted to know why the suppression is applied to the LOAD side of the alternator diodes. Perhaps you two could stop slapping each others butts long enough to try to answer that question. True, there are none so ignorant as those who refuse to learn. Now that we're even on stupid witticisms, can you try for a technical answer? Ed |
Are zap stoppers really needed on alternators?
Ed Price wrote: Well, pardon me for asking you to address my question. In case you didn't remember, since it always seems to slip your attention during your posts, I wanted to know why the suppression is applied to the LOAD side of the alternator diodes. Perhaps you two could stop slapping each others butts long enough to try to answer that question. True, there are none so ignorant as those who refuse to learn. Now that we're even on stupid witticisms, can you try for a technical answer? OK, I am going to try one more time. What I am about to say was verified yesterday afternoon by Randy Johnson, formerly of Cruising Equipment and developer of the Zap-Stop and confirmed by the tech support people at Balmar and Leece-Neville. When an alternator is producing a significant percentage of its capacity to a load, be it a battery, motor or other device and that load is suddenly removed the output voltage of the alternator will rise. While the rectifier diodes can handle higher than normal amperage for short periods they cannot tolerate voltages significantly over their rating for even an instant. Therefore if this voltage rise is not checked there is a very good possibility that the alternator rectifier diodes will be damaged. The physical law of conservation of energy says that the amount of energy output by a device must equal the amount supplied to it. The power output of an alternator is determined by the amount of energy being supplied by the engine. The amount supplied is a function of RPM and torque. The torque is governed by the intensity of the magnetic field. As the engine speed cannot normally be adjusted quickly the regulator is used to control the magnetic field. This control is fast but it is not instantaneous. As the field collapses, a back EMF is inducted in the field coil slowing the process. Therefore there is a lag in reducing the total power being produced. FOR AN INSTANT TOTAL POWER REMAINS THE SAME. Power is volts times amps. As there is no demand for the amps basic math says that the voltage must rise. The current practice for preventing damage to the regulator diodes is to place a sacrificial diode between the alternator output and ground to provide an alternate path for the energy. Both of the alternator manufacturers I talked to strongly recommend the installation of one of these diodes whenever there is a possibility that a heavy load might be suddenly dropped. This diode will not conduct until the voltage exceeds a certain preset limit determined by its construction. It has only one function: To provide a way for the alternator to shed the surplus current so that the voltage will not rise to a damaging level. The rectifier sees only a slight drop in current demand and a slight rise in voltage. It does not know anything about whether it is supplying the original load or the protecting diode. The protecting diode however has to bite the bullet and very often gives its life in the process but it will last long enough to handle the surge for the fraction of a second required to get the power output below a damaging level. That is about as simple as I can get it. If that is not satisfactory, go talk to JAX. He is more on your level. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Are zap stoppers really needed on alternators?
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Are zap stoppers really needed on alternators?
Read an application note from the load dump protector
manufacturer (when still called SGS Thompson) about 1996. It's more than just putting a suppressor diode on output or using larger components. As they noted: The protection at the alternator level is a quite new concept and all the technical problems do not seem to be completely solved. The problem has long been known and has long created problems. Solutions have been installed for decades. Still an adaquate design has not been perfected. My first experience was in early 1960s when alternators used germanium diodes. The problem has been understood that long. Thompson Electronics does make load dump suppressors and are a major electronic supplier to GM. However I don't know if GM uses the parts (model numbers provided in the previous post) from Thompson. As Glenn Ashmore has so accurately noted, load dump is a serious electrical threat even to powered electronics. Simply look at the voltages that can exist on a 12 volts system (which is why electronics whose specifications specifically state load dump protection cost more). Especially susceptible are boat power systems. Master battery switch must be designed 'make before break'. IOW during battery switchover, a battery must be always connected to alternator. Better designs even transition the switchover to soften the 'change of load'. Cars typically don't suffer as easily BUT will be more susceptible as more functions become electrical (ie steering) and voltage is raise from 12 volts to the new 42 volt standards. Glenn Ashmore wrote: GregS wrote: Sounds like they need to make them properly, with higher voltage diodes. It is a matter of size and economics. Diodes capable of handling high voltages and high amperages are large and expensive. Leece-Neville makes such a rectifier for heavy EMT and construction equipment but it is a box separate from the alternator and cost more than any of us would want to pay. 99% of the alternator installations are automotive and do not have master battery disconnects. Also automotive alternators seldom run at a significant percentage of rated capacity for very long. The major load last for only a few minutes to replenish the cranking power. Boats with house banks on the other hand usually do have master switches and either the switch must have a capability to disconnect the field current before opening the battery circuit or a bypass diode of some kind on the alternator. To do otherwise is a pretty good bet that eventually you will fry the rectifier diodes. Unfortunately boats make up a microscopic percentage of the alternator market so this type of protection is not provide for. ... |
Are zap stoppers really needed on alternators?
"Glenn Ashmore" wrote in message ... Ed Price wrote: Well, pardon me for asking you to address my question. In case you didn't remember, since it always seems to slip your attention during your posts, I wanted to know why the suppression is applied to the LOAD side of the alternator diodes. Perhaps you two could stop slapping each others butts long enough to try to answer that question. True, there are none so ignorant as those who refuse to learn. Now that we're even on stupid witticisms, can you try for a technical answer? OK, I am going to try one more time. What I am about to say was verified yesterday afternoon by Randy Johnson, formerly of Cruising Equipment and developer of the Zap-Stop and confirmed by the tech support people at Balmar and Leece-Neville. When an alternator is producing a significant percentage of its capacity to a load, be it a battery, motor or other device and that load is suddenly removed the output voltage of the alternator will rise. While the rectifier diodes can handle higher than normal amperage for short periods they cannot tolerate voltages significantly over their rating for even an instant. Therefore if this voltage rise is not checked there is a very good possibility that the alternator rectifier diodes will be damaged. The physical law of conservation of energy says that the amount of energy output by a device must equal the amount supplied to it. The power output of an alternator is determined by the amount of energy being supplied by the engine. The amount supplied is a function of RPM and torque. The torque is governed by the intensity of the magnetic field. As the engine speed cannot normally be adjusted quickly the regulator is used to control the magnetic field. This control is fast but it is not instantaneous. As the field collapses, a back EMF is inducted in the field coil slowing the process. Therefore there is a lag in reducing the total power being produced. FOR AN INSTANT TOTAL POWER REMAINS THE SAME. Power is volts times amps. As there is no demand for the amps basic math says that the voltage must rise. The current practice for preventing damage to the regulator diodes is to place a sacrificial diode between the alternator output and ground to provide an alternate path for the energy. Both of the alternator manufacturers I talked to strongly recommend the installation of one of these diodes whenever there is a possibility that a heavy load might be suddenly dropped. This diode will not conduct until the voltage exceeds a certain preset limit determined by its construction. It has only one function: To provide a way for the alternator to shed the surplus current so that the voltage will not rise to a damaging level. The rectifier sees only a slight drop in current demand and a slight rise in voltage. It does not know anything about whether it is supplying the original load or the protecting diode. The protecting diode however has to bite the bullet and very often gives its life in the process but it will last long enough to handle the surge for the fraction of a second required to get the power output below a damaging level. That is about as simple as I can get it. If that is not satisfactory, go talk to JAX. He is more on your level. -- Glenn Ashmore Thanks for the more lucid explanation, despite the several gratuitous insults. After reading your new information, I'll even go so far as to retract my quip of a totally bogus explanation of energy within the alternator; I now realize you were being more condescending than obscure. To me, fast is microseconds or nanoseconds, and I guess you just live in a slower world. It further helps to hear that the Zap-stop only conducts a current similar to the original load, and that for only a few hundred milliseconds. That's probably why connecting the protection to the output of the alternator doesn't kill the alternator diodes. But that leads to another issue. You said the protection diode often fails!! Question 1.: Why does the protection diode "often fail" if it's drawing the same load as the alternator diodes? Question 2.: You assert that the protection diode "will last long enough." Is this some kind of smart silicon, in that it knows when it's OK to die? Again, I'm not familiar with your world, but devices that I have seen in which there is a failure under load usually fail under full load, or at least not when most of the load has gone away. Whenever I cook off a diode, it usually dies a lot faster than a couple of hundred milliseconds. I would think that the protection diode would be sized so that it rarely fails. After all, isn't a protection diode failure just another way of describing load shedding? IIRC, you said that diodes that could handle typical alternator currents could be had at Digikey for under a buck. Maybe you should refer Xentrex, too. Ed |
Are zap stoppers really needed on alternators?
The tone of the debate was set by you. I was only responding.
The field coil is a gigantic inductor compared to the inductors used in high speed electronics like computers and radio frequency equipment. When the field current is removed the time it takes for the magnetic field to collapse is related to the strength of the field and the number and centerline spacing of the turns. Strong fields take a lot of time to collapse through a lot of turns of relatively thick tightly wound wire so we are talking about milliseconds rather than micro or nanoseconds. Diodes are rated by the voltage and amperage they can take and how long they can take the power. The larger the combination gets the more expensive and larger the diode gets. We are facing the limits of size and economics. The Zap Stop is sized to "do the job" without pricing itself out of the market. In most cases it will rarely fail but the potential is still there. Probably the worst case would be dropping the load on a large cold alternator bulk charging at full power. All that power that was going through a 4/0 cable now flows through a few inches of #14 wire and a fraction of an inch of diode material. That can generate a lot of heat very quickly. The newer Zap Stops have a fuse in series with the diode. The idea being that in the time it takes for the fuse to blow the field strength drops below the damaging level. It would be nice however if they added a little circuitry and an LED to indicate when the diode had been fried. Right now the only way to know that your alternator is protected is to periodically test it with a multimeter. The diode that the Zap Stop uses probably only cost a dollar or two but the case probably cost another couple of bucks and it might take 5 minutes worth of labor to put it together and stick it in a box. Total manufacturing cost is probably under 5 bucks. BUT, a general rule of thumb is that manufacturing cost of any item should be no more than 25% of retail price. If you put the word "marine" in the description it can drop to 20%. Ed Price wrote: Thanks for the more lucid explanation, despite the several gratuitous insults. After reading your new information, I'll even go so far as to retract my quip of a totally bogus explanation of energy within the alternator; I now realize you were being more condescending than obscure. To me, fast is microseconds or nanoseconds, and I guess you just live in a slower world. It further helps to hear that the Zap-stop only conducts a current similar to the original load, and that for only a few hundred milliseconds. That's probably why connecting the protection to the output of the alternator doesn't kill the alternator diodes. But that leads to another issue. You said the protection diode often fails!! Question 1.: Why does the protection diode "often fail" if it's drawing the same load as the alternator diodes? Question 2.: You assert that the protection diode "will last long enough." Is this some kind of smart silicon, in that it knows when it's OK to die? Again, I'm not familiar with your world, but devices that I have seen in which there is a failure under load usually fail under full load, or at least not when most of the load has gone away. Whenever I cook off a diode, it usually dies a lot faster than a couple of hundred milliseconds. I would think that the protection diode would be sized so that it rarely fails. After all, isn't a protection diode failure just another way of describing load shedding? IIRC, you said that diodes that could handle typical alternator currents could be had at Digikey for under a buck. Maybe you should refer Xentrex, too. Ed -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Are zap stoppers really needed on alternators?
don't be upset, Ed trolls to test your conviction and real understanding.
"Glenn Ashmore" wrote in message ... The tone of the debate was set by you. I was only responding. The field coil is a gigantic inductor compared to the inductors used in high speed electronics like computers and radio frequency equipment. When the field current is removed the time it takes for the magnetic field to collapse is related to the strength of the field and the number and centerline spacing of the turns. Strong fields take a lot of time to collapse through a lot of turns of relatively thick tightly wound wire so we are talking about milliseconds rather than micro or nanoseconds. Diodes are rated by the voltage and amperage they can take and how long they can take the power. The larger the combination gets the more expensive and larger the diode gets. We are facing the limits of size and economics. The Zap Stop is sized to "do the job" without pricing itself out of the market. In most cases it will rarely fail but the potential is still there. Probably the worst case would be dropping the load on a large cold alternator bulk charging at full power. All that power that was going through a 4/0 cable now flows through a few inches of #14 wire and a fraction of an inch of diode material. That can generate a lot of heat very quickly. The newer Zap Stops have a fuse in series with the diode. The idea being that in the time it takes for the fuse to blow the field strength drops below the damaging level. It would be nice however if they added a little circuitry and an LED to indicate when the diode had been fried. Right now the only way to know that your alternator is protected is to periodically test it with a multimeter. The diode that the Zap Stop uses probably only cost a dollar or two but the case probably cost another couple of bucks and it might take 5 minutes worth of labor to put it together and stick it in a box. Total manufacturing cost is probably under 5 bucks. BUT, a general rule of thumb is that manufacturing cost of any item should be no more than 25% of retail price. If you put the word "marine" in the description it can drop to 20%. Ed Price wrote: Thanks for the more lucid explanation, despite the several gratuitous insults. After reading your new information, I'll even go so far as to retract my quip of a totally bogus explanation of energy within the alternator; I now realize you were being more condescending than obscure. To me, fast is microseconds or nanoseconds, and I guess you just live in a slower world. It further helps to hear that the Zap-stop only conducts a current similar to the original load, and that for only a few hundred milliseconds. That's probably why connecting the protection to the output of the alternator doesn't kill the alternator diodes. But that leads to another issue. You said the protection diode often fails!! Question 1.: Why does the protection diode "often fail" if it's drawing the same load as the alternator diodes? Question 2.: You assert that the protection diode "will last long enough." Is this some kind of smart silicon, in that it knows when it's OK to die? Again, I'm not familiar with your world, but devices that I have seen in which there is a failure under load usually fail under full load, or at least not when most of the load has gone away. Whenever I cook off a diode, it usually dies a lot faster than a couple of hundred milliseconds. I would think that the protection diode would be sized so that it rarely fails. After all, isn't a protection diode failure just another way of describing load shedding? IIRC, you said that diodes that could handle typical alternator currents could be had at Digikey for under a buck. Maybe you should refer Xentrex, too. Ed -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Are zap stoppers really needed on alternators?
"phil" wrote in message et... don't be upset, Ed trolls to test your conviction and real understanding. "Glenn Ashmore" wrote in message ... The tone of the debate was set by you. I was only responding. The field coil is a gigantic inductor And thank YOU, Phil, for your cogent contributions to this discussion. The definition of a troll is not someone who poses a question which confuses you. The best trolls usually reply to any reasonable answer with a new set of conditions which defeat the original answer. If they are fast enough, they can keep sliding out from under your logical hammer. I will admit that I'm quite skeptical of the claims of almost any marketer. When someone tells me that I need their latest gadget to protect a system that is not known for failure, then the little BS flag starts to wiggle. At the beginning of this thread, I went to the Xentrex site, and found market hype, not engineering data. No schematics, no info on joules ratings, no waveforms of with and without a Zap-stop. It took several exchanges just to understand what this thing really does. There are a vast number of auto owners, with alternator systems, who will NEVER experience 60-amp load dumps. And there are many, many small boat owners whose electrical systems are close copies of automotive systems, and they also operate under nearly the same conditions as a car. So that's another whole cohort that will NEVER see those 60-amp load dumps. So who does experience these load dump conditions? How often will Glenn, in his cruiser, be pumping 60 amps back into his battery bank? And for how long? And with what probability that he will do a trick with the battery changeover switch during that short period of exposure? So help me out here, Phil; what class of vessel often sees 60-amp charging currents? Does that class of vessel usually have switch-twiddling idiots running the below-decks division? It seems to me that the Zap-stop is being hyped as needed for everyone with an alternator, while the conditions of 60-amp load dumps are experienced by only a small slice of small boat owners. Or maybe I'm just a troll. Ed |
Are zap stoppers really needed on alternators?
I will be pumping over 200 amps for as long as an hour every day while
cruising. I had to go back and look at some of your previous posts to figure out why you are thinking the way you are. Then I found the post about having a 0-75 MPH speedo and realized that you are a hot rod ski boater with no idea of how a cruising boat works. A typical 35' to 50' cruising boat with a well balanced electrical system will have anywhere from 350 to 1200 amp hours of battery bank and will regularly draw it from 75% to 50% to keep the charging cycle in the bulk current range. They will have an alternator capable of outputting 20 to 25% of the bank's capacity per hour and run it once or twice a day for up to an hour at as close to full capacity as possible. That is what those fancy three stage regulators with temperature sensors and recombinant caps are for. As an example, my boat will have a pretty heavy duty system but it is not as large as some in that size range and not all that much larger than most. It is 800 amp hours in four L16HC batteries charged by a 250 amp brushless Niehoff fire truck alternator with an external three stage regulator and external rectifier. The energy budget calls for charging and making water for 45 minutes to an hour every day while cruising. Should a guest unknowingly turn the master battery switch during that time I could be out about $1,000. In this situation, which is not unusual for a cruiser, a $25 investment in a Zap Stop is a no brainer. The single most common reason for failures in cruising boat alternators is load dump spikes with bearing failures a distant second. OTOH, a ski boat with only a cranking battery, no master battery switch and a stock 60 amp alternator would never have to worry. Ed Price wrote: snip There are a vast number of auto owners, with alternator systems, who will NEVER experience 60-amp load dumps. And there are many, many small boat owners whose electrical systems are close copies of automotive systems, and they also operate under nearly the same conditions as a car. So that's another whole cohort that will NEVER see those 60-amp load dumps. So who does experience these load dump conditions? How often will Glenn, in his cruiser, be pumping 60 amps back into his battery bank? And for how long? And with what probability that he will do a trick with the battery changeover switch during that short period of exposure? So help me out here, Phil; what class of vessel often sees 60-amp charging currents? Does that class of vessel usually have switch-twiddling idiots running the below-decks division? It seems to me that the Zap-stop is being hyped as needed for everyone with an alternator, while the conditions of 60-amp load dumps are experienced by only a small slice of small boat owners. Or maybe I'm just a troll. Ed -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Are zap stoppers really needed on alternators?
So Ed....
Again, I will ask you just like I did during our EMC discussion, what percentage of boaters have an engineering degree and would understand joules, ohms, volts, ohms law, etc. to even have an inkling of what the information meant if it were indeed included on the web page? Even if it were included, how would it relavent unless the matching information were provided by the alternator manufacturer under load dump conditions? I find it interesting that most people don't have a clue how electricity works and couldn't troubleshoot a light switch, much less understand alternator load dump waveforms versus load and rpm, joules dumped, whether their alternator diodes were damaged, and on and on. How many people come on here and ask "I have no spark and I replaced everything such as the coil, plug wires, plugs, coil driver components (mechanical or electronic), and there still is no spark". I would suggest most people would just get a protector and just feel good that there was some additional protection from battery disconnects. To me, load dump is not mysterious, I deal with it all the time in my job (don't ask cause I won't tell you). Phil "Ed Price" wrote in message news:IGmSa.1006$Ye.415@fed1read02... "phil" wrote in message et... don't be upset, Ed trolls to test your conviction and real understanding. "Glenn Ashmore" wrote in message ... The tone of the debate was set by you. I was only responding. The field coil is a gigantic inductor And thank YOU, Phil, for your cogent contributions to this discussion. The definition of a troll is not someone who poses a question which confuses you. The best trolls usually reply to any reasonable answer with a new set of conditions which defeat the original answer. If they are fast enough, they can keep sliding out from under your logical hammer. I will admit that I'm quite skeptical of the claims of almost any marketer. When someone tells me that I need their latest gadget to protect a system that is not known for failure, then the little BS flag starts to wiggle. At the beginning of this thread, I went to the Xentrex site, and found market hype, not engineering data. No schematics, no info on joules ratings, no waveforms of with and without a Zap-stop. It took several exchanges just to understand what this thing really does. There are a vast number of auto owners, with alternator systems, who will NEVER experience 60-amp load dumps. And there are many, many small boat owners whose electrical systems are close copies of automotive systems, and they also operate under nearly the same conditions as a car. So that's another whole cohort that will NEVER see those 60-amp load dumps. So who does experience these load dump conditions? How often will Glenn, in his cruiser, be pumping 60 amps back into his battery bank? And for how long? And with what probability that he will do a trick with the battery changeover switch during that short period of exposure? So help me out here, Phil; what class of vessel often sees 60-amp charging currents? Does that class of vessel usually have switch-twiddling idiots running the below-decks division? It seems to me that the Zap-stop is being hyped as needed for everyone with an alternator, while the conditions of 60-amp load dumps are experienced by only a small slice of small boat owners. Or maybe I'm just a troll. Ed |
Are zap stoppers really needed on alternators?
You're just a troll.
The cruisers that buy other Xantrex products, like the Link 2000R monitor/regulator are the people that frequently charge over 60 Amps at a time. If I'm at anchor for an extended period, I'll likely be running an engine an hour a day, charging at about 85 Amps. Although many new cruising boats don't have the "Big Red Switch," almost all older boats have one, just waiting for the mischievous nephew, or helpful brother-in-law to flip. I know of one case where a friend, and experienced oat owner, had a brain stall and flipped the switch, killing a GPS and sounder. "Ed Price" wrote in message news:IGmSa.1006$Ye.415@fed1read02... "phil" wrote in message et... don't be upset, Ed trolls to test your conviction and real understanding. "Glenn Ashmore" wrote in message ... The tone of the debate was set by you. I was only responding. The field coil is a gigantic inductor And thank YOU, Phil, for your cogent contributions to this discussion. The definition of a troll is not someone who poses a question which confuses you. The best trolls usually reply to any reasonable answer with a new set of conditions which defeat the original answer. If they are fast enough, they can keep sliding out from under your logical hammer. I will admit that I'm quite skeptical of the claims of almost any marketer. When someone tells me that I need their latest gadget to protect a system that is not known for failure, then the little BS flag starts to wiggle. At the beginning of this thread, I went to the Xentrex site, and found market hype, not engineering data. No schematics, no info on joules ratings, no waveforms of with and without a Zap-stop. It took several exchanges just to understand what this thing really does. There are a vast number of auto owners, with alternator systems, who will NEVER experience 60-amp load dumps. And there are many, many small boat owners whose electrical systems are close copies of automotive systems, and they also operate under nearly the same conditions as a car. So that's another whole cohort that will NEVER see those 60-amp load dumps. So who does experience these load dump conditions? How often will Glenn, in his cruiser, be pumping 60 amps back into his battery bank? And for how long? And with what probability that he will do a trick with the battery changeover switch during that short period of exposure? So help me out here, Phil; what class of vessel often sees 60-amp charging currents? Does that class of vessel usually have switch-twiddling idiots running the below-decks division? It seems to me that the Zap-stop is being hyped as needed for everyone with an alternator, while the conditions of 60-amp load dumps are experienced by only a small slice of small boat owners. Or maybe I'm just a troll. Ed |
Are zap stoppers really needed on alternators?
"phil" wrote in message et... So Ed.... Again, I will ask you just like I did during our EMC discussion, what percentage of boaters have an engineering degree and would understand joules, ohms, volts, ohms law, etc. to even have an inkling of what the information meant if it were indeed included on the web page? Even if it were included, how would it relavent unless the matching information were provided by the alternator manufacturer under load dump conditions? I find it interesting that most people don't have a clue how electricity works and couldn't troubleshoot a light switch, much less understand alternator load dump waveforms versus load and rpm, joules dumped, whether their alternator diodes were damaged, and on and on. How many people come on here and ask "I have no spark and I replaced everything such as the coil, plug wires, plugs, coil driver components (mechanical or electronic), and there still is no spark". I would suggest most people would just get a protector and just feel good that there was some additional protection from battery disconnects. To me, load dump is not mysterious, I deal with it all the time in my job (don't ask cause I won't tell you). Phil Phil: You are truly a wonderful and mysterious duck. I will not ask your occupation, partially because I do not care, and because, I assume, should you tell me, then I suppose you'll have to kill me. I do find it troubling that, as in the EMC discussion, you are again arguing for the cause of ignorance. You say that Zap-stop shouldn't need to provide technical info since the alternator manufacturers don't provide load-dump info. And then you say that most in this group wouldn't know what the information meant anyway. OK, if that's your opinion, I can't change your mind. Ed |
Are zap stoppers really needed on alternators?
"Glenn Ashmore" wrote in message ... I will be pumping over 200 amps for as long as an hour every day while cruising. I had to go back and look at some of your previous posts to figure out why you are thinking the way you are. Then I found the post about having a 0-75 MPH speedo and realized that you are a hot rod ski boater with no idea of how a cruising boat works. A typical 35' to 50' cruising boat with a well balanced electrical system will have anywhere from 350 to 1200 amp hours of battery bank and will regularly draw it from 75% to 50% to keep the charging cycle in the bulk current range. They will have an alternator capable of outputting 20 to 25% of the bank's capacity per hour and run it once or twice a day for up to an hour at as close to full capacity as possible. That is what those fancy three stage regulators with temperature sensors and recombinant caps are for. As an example, my boat will have a pretty heavy duty system but it is not as large as some in that size range and not all that much larger than most. It is 800 amp hours in four L16HC batteries charged by a 250 amp brushless Niehoff fire truck alternator with an external three stage regulator and external rectifier. The energy budget calls for charging and making water for 45 minutes to an hour every day while cruising. Should a guest unknowingly turn the master battery switch during that time I could be out about $1,000. In this situation, which is not unusual for a cruiser, a $25 investment in a Zap Stop is a no brainer. The single most common reason for failures in cruising boat alternators is load dump spikes with bearing failures a distant second. OTOH, a ski boat with only a cranking battery, no master battery switch and a stock 60 amp alternator would never have to worry. Ed Price wrote: Very illuminating, Glenn. Now I understand why your posts have trouble answering a question and often ramble off into an insulting lecture. You are obviously distracted by the rigors of searching previous postings looking for clues about the poster's lifestyle and recreational habits. I find it truly hilarious that you have concluded that I am a "hot rod ski boater." Based on that profound logic, I suppose that having a DVM with a 1200 VAC range makes you an electrician? You are becoming a pretentious twit. One of the first things I did when you started lecturing me was to visit your little sailboat construction site. Actually, for an unpleasant person, you do nice work. If I lived near you, I would be happy to see you complete the project and sail over the horizon. But I am learning some interesting things about you and your cutter. I always thought that sailors chose sail because they liked the "off the grid" lifestyle. They wanted to get out there with the lee scuppers sloshing green water, close to nature and in touch with the long heritage of men against the sea. At least that's what they always said when I offered them a tow off a sand bar. They liked to look down on "stink-potters" just the way you casually insult small powerboat owners. You seem to have some really hearty electrical needs. Yeah, I guess I'm really out of touch with the average cruising sailor. I mean, on a 31-foot twin engine cruiser I had, once I shut down the engines, my electrical load was only an anchor light, a couple of 12 VDC cabin lights, sometimes a half-amp radio, a minute or so of rare bilge pump operation, a 30-second burst of the toilet macerator pump, and a rare burst of the freshwater pressure pump. Then, I had a 50-foot down-east style diesel trawler. It was more primitive, without an electric head (see how long ago that was?), but I did have a big battery bank, because starting the diesel (GM 6-71) was a tough load. And, it was pretty leaky, with two Rule 1200 GPH pumps disturbingly active. I guess your way of sailing must include microwave ovens and color TV's and full-time radar and autohelm. I'm not criticizing your choices, just trying to account for your electrical budget. Now, you said you had 800 amp-hours batteries, and you plan to use about 65% of that capacity in one day. That's 520 amp-hours, and with 12 VDC, that's 6240 watt-hours. Averaged out evenly, that's equivalent to a continuous 23 amp drain. And then, to put that charge back in one hour, that implies a charging current of 520 amps. But since your alternator has a capacity of 250 amps, you will need to run the charge for two hours. If not, then you will hit full discharge on maybe the third or fourth day. But aside from the schedule, what is your projected load budget? Meanwhile, curb your imagination. I'm presently doing a restoration on a 14-foot steel displacement hull vessel with a rated 36 HP gasoline engine. As you can imagine, hull speed is quite a bit less than 75 MPH. Maybe if I had your battery pack, I could get it to plane for a couple of minutes! Ed |
Are zap stoppers really needed on alternators?
The reason for the 800 amp hour bank is that I will have two large
computers, a 3000 watt inverter, SSB radio and a rather powerful autopilot. All of which will eat a fair number of amps. I have estimated my daily energy budget underway to be between 180 and about 225 amp hours. Two other factors determined the bank size. The first is that deep cycle batteries should never ne discharged below 50% to preserve their useful life. That limits my usable power to 400 amps. The second is that I would like to keep engine time to a minimum. All the systems that use engine power, charging, watermaking and refrigeration are designed to restore themselves in one hour of engine time per day. Up to about 75-80% charge, deep cycle batteries can accept a charge current of up to 25% of their capacity. As they approach full charge the rate has to be reduced substantially. That sets an upper limit for daily charging at about 80%. The result is a net usable capacity of 30% or about 240 amp hours. As I said, You set the tone of the conversation. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Are zap stoppers really needed on alternators?
Ok here's my take on it.
If you need a zap stopper then you should rewire your system. I see 1 or 2 boats every year that has problems because someone turned off the switch while the alt was running. When I get finished it doesn't matter what they do with the switch as i try to murphy-proof the system. The output of the big alternator should go direct to the big bank of batteries. The sense for this alternator must go back to same bank of batteries. Now you can use the switch to combine the banks have more then one switch to do other things with, have a battery combiner in curcuit or even an isolater to auto slow charge the engine banks (at main bank voltage minus isolater drop). Why are we having this didcussion if your boat is wired up right you need no zap stop. The engine manufacture can not do it right as he has no idea how your banks are hooked up he can only put alternator output to starter. You must wire it up right. |
Are zap stoppers really needed on alternators?
yup...I guess I am a mysterious duck. And, that's fine with me. Keeps
everyone off balance. My position is that no one is going to learn about load dump and emc characteristics / countermeasures by reading this newsgroup. If they truly were interested, they would research the topic on google or visit their local library. "Ed Price" wrote in message news:1GrTa.3104$Ye.475@fed1read02... "phil" wrote in message et... So Ed.... Again, I will ask you just like I did during our EMC discussion, what percentage of boaters have an engineering degree and would understand joules, ohms, volts, ohms law, etc. to even have an inkling of what the information meant if it were indeed included on the web page? Even if it were included, how would it relavent unless the matching information were provided by the alternator manufacturer under load dump conditions? I find it interesting that most people don't have a clue how electricity works and couldn't troubleshoot a light switch, much less understand alternator load dump waveforms versus load and rpm, joules dumped, whether their alternator diodes were damaged, and on and on. How many people come on here and ask "I have no spark and I replaced everything such as the coil, plug wires, plugs, coil driver components (mechanical or electronic), and there still is no spark". I would suggest most people would just get a protector and just feel good that there was some additional protection from battery disconnects. To me, load dump is not mysterious, I deal with it all the time in my job (don't ask cause I won't tell you). Phil Phil: You are truly a wonderful and mysterious duck. I will not ask your occupation, partially because I do not care, and because, I assume, should you tell me, then I suppose you'll have to kill me. I do find it troubling that, as in the EMC discussion, you are again arguing for the cause of ignorance. You say that Zap-stop shouldn't need to provide technical info since the alternator manufacturers don't provide load-dump info. And then you say that most in this group wouldn't know what the information meant anyway. OK, if that's your opinion, I can't change your mind. Ed |
On Wed, 16 Jul 2003 03:03:48 -0700, "Ed Price"
wrote: "Glenn Ashmore" wrote in message ... First of all, teh Zap Stop is not intended to protect anything from external spikes. There are very few situations on a boat that will cause a damaging spike back into the alternator other than a lightning strike and in that case all bets are off. The Zap Stop is only intended to protect the alternator from self destructing from a load dump. It does nothing else. It does this by clamping the voltage lower than the damaging point for the rectifier. In a load dump the voltage spike is what fries the rectifier diodes not the amperage. And how do you "clamp" a voltage when a voltage source is trying to drive it higher? As the Zap-stop does, by presenting a conductive path that has a very low resistance. The current is limited only by the source's internal resistance. I have no idea what the internal resistance of a large alternator is, but I would guess maybe 0.01 ohms. The important point is that you have to be able to sink a lot of current during the alternator's field winding voltage excursion. Putting the protective device on the load side of the alternator diodes is a solution that requires a heavy current draw through the alternator diodes during a protective event. For illustration, lets say we have a big honkin' 250 amp Balmar cranking out full power 15 volts into the house bank (3,750 watts) when somebody turns the master switch and the output voltage starts to rise. The regulator is still supplying the same current to the field and the RPM has not changed. As no additional energy is being supplied to the alternator the total power output remains the same. Absolutely bogus assumption about power output remaining constant. I am assuming that your alternator has an electronic, not a mechanical, regulation scheme. Are you claiming that the regulation can track load variations during normal operation, but, if the load is suddenly shed, it takes hundreds of milliseconds to react?! Power is volts * amps so as the voltage rises the amperage has to drop. For that 200-300 milliseconds that it takes for the regulator to adjust the field current the zenier has to absorb that 3,750 watts of excess power. Diodes that can handle this amount of power for that length of time are not hard to find. Digikey sells them for about a buck apiece. I checked my Digikey catalog, but can't find any "zenier" diodes. Perhaps you could fix your spull chucker; your consistent use of the wrong spelling is beginning to bug me, as real experts know the names of their tools. You know, you pound nails with a hammer, and discussing nail technology is disconcerting when the other guy keeps talking about his hummer. But regardless of how much diodes cost, where you buy them, and whether they will fail trying to carry x kiloamps for y milliseconds, the initial point I asked was why it was good practice to put the protection on the load side of the alternator diodes. Telling me that you can get away with it is not a good answer. Ed Ed - there is a simple answer. VOLTAGE is the killer, not current. What determines the maximum output of an alternator? Unlike generators that had a current regulator, alternators are regulated by the internal resistance of the stator circuit. The diodes in an average 100 amp alternator are good for close to 200 amps (continuous) of total output, but only for about 150 volts. Now 150 volts is MORE than adequate for normal circumstances, but when you experience a "load dump" the voltage can very quickly exceed even 300 or 600 volts for a short time (minimum of number of stator poles of cycles) as the collapsing magnetic field in the stator collapses, inducing voltage in the field, which can also contribute to the voltage spike). Without a load of some sort to keep that voltage tamed down, the voltage rating of the diodes can be grossly exceded. The current flow, being extremely short, does not get the diodes hot enough to fail from overcurrent, as the current is more or less self limitting. The Zap stopper shunts this current to ground, keeping the voltage well controlled for that very short time - and again, the current is not high long enough to heat the slow-blow protection fuse enough to pop it. The trans/zorb or zap stopper can also protect against the same kind of spikes should the field circuit open under load - and the collapsing field current induces a (negative?) spike in the stator which passes through the diodes and is clamped by the zap stopper. Now, if you attempted to install the zap-stopper on the stator side of the rectifying diodes, you could have a serious problem - as there is AC on the stator, not DC. You would need 2 zap stoppers per phase - or one per diode - to clamp the voltage internally. That is SIX on an average 3 phase alternator. And ONE on the rectified side does the job, just as well. |
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