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#1
posted to rec.boats.electronics
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Can an alternator be to big?
Actually reducing the alternator RPM is the idea. This thing puts out
200Amps at an alternator speed under 2000 RPM. With the pulleys I have now that is an engine speed of about 800 RPM. I need to get the engine turning faster or the power will be all torque and no speed and Larry's prediction of gloom and doom might come true. A pair of BX belts can handle plenty of HP but not at such low speeds. After some research I found some interesting things about this monster. There are actually two rotors on the same shaft. One is high power permanent magnets and the other is a regular Lundell claw & field coil. With the field coil off the magnets will drive the alternator to 200 amps at 4,000 RPM. If more power is needed to maintain voltage the field coil is energized to add to the flux and produce up to 305 amps. If less power is needed the coil is reversed to cancel out the flux field. Net result is a 70% increase in efficiency and a corresponding reduction in heat build up but to get minimum output the field coil has to be driven at full power backwards. The down side is you can't use a 3 stage regulator. This puppy is designed to crank out power for lights, inverters and equipment. Control is strictly on the output voltage so it stays in bulk stage until the batteries can't take any more. This is going to take some more thought. For the price though it would be a good temporary high output spare. -- 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 "Andina Marie" wrote in message ps.com... I hope you were increasing both pulleys so the alternator RPM was the same? If the alternator sucks up too many horsepower, especially when docking or emergencies, a field disconnect switch can be added to remove the load temporarily. |
#2
posted to rec.boats.electronics
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Can an alternator be to big?
Glenn Ashmore wrote:
Actually reducing the alternator RPM is the idea. This thing puts out 200Amps at an alternator speed under 2000 RPM. With the pulleys I have now that is an engine speed of about 800 RPM. I need to get the engine turning faster or the power will be all torque and no speed and Larry's prediction of gloom and doom might come true. A pair of BX belts can handle plenty of HP but not at such low speeds. Actually, the alternator will put out whatever the battery and loads require. Unless you are charging a huge battery bank and/or have 200 A load connected to it, it won't put out that much. Given the electrical (and mechanical) losses, the input HP will be whatever are needed to provide the electrical output. The larger alternator will have lower electrical losses, but higher mechanical. All in all, this unit won't present a mechanical load significantly different than a smaller alternator. After some research I found some interesting things about this monster. There are actually two rotors on the same shaft. One is high power permanent magnets and the other is a regular Lundell claw & field coil. With the field coil off the magnets will drive the alternator to 200 amps at 4,000 RPM. If more power is needed to maintain voltage the field coil is energized to add to the flux and produce up to 305 amps. If less power is needed the coil is reversed to cancel out the flux field. Net result is a 70% increase in efficiency and a corresponding reduction in heat build up but to get minimum output the field coil has to be driven at full power backwards. This unit must be matched to the appropriate regulator. If you didn't get one with the alternator, the deal may not have been that good. The down side is you can't use a 3 stage regulator. This puppy is designed to crank out power for lights, inverters and equipment. Control is strictly on the output voltage so it stays in bulk stage until the batteries can't take any more. This is going to take some more thought. For the price though it would be a good temporary high output spare. -- 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 "Andina Marie" wrote in message ps.com... I hope you were increasing both pulleys so the alternator RPM was the same? If the alternator sucks up too many horsepower, especially when docking or emergencies, a field disconnect switch can be added to remove the load temporarily. -- Paul Hovnanian ------------------------------------------------------------------ Klein bottle for rent -- inquire within |
#3
posted to rec.boats.electronics
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Can an alternator be to big?
"Paul Hovnanian P.E." wrote Actually, the alternator will put out whatever the battery and loads require. Unless you are charging a huge battery bank and/or have 200 A load connected to it, it won't put out that much. Given the electrical (and mechanical) losses, the input HP will be whatever are needed to provide the electrical output. The larger alternator will have lower electrical losses, but higher mechanical. All in all, this unit won't present a mechanical load significantly different than a smaller alternator. That's just it. There will definitely be a heavy load on it. When it cranks up every morning it will be seeing a 900AH battery bank ready to take the first 225 amps in bulk mode. This unit must be matched to the appropriate regulator. If you didn't get one with the alternator, the deal may not have been that good. It has the regulator built in. Pretty interesting one too. Even has a battery voltage sense connection. However the regulator does not have a way to change from bulk to absorption to float modes and there is no equalization. The shore power charger can handle the equalization and with my normal use pattern of 50% to 85% charge will rarely need float except at the dock but it would be nice to have optomized bulk and absorption ability. -- 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 |
#4
posted to rec.boats.electronics
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Can an alternator be to big?
Glen,
Have you considered biasing the voltage sense line, to adjust the regulator output voltage? Peter Albright, Tampa, FL "Glenn Ashmore" wrote in message news:BV3ug.44$ok5.9@dukeread01... "Paul Hovnanian P.E." wrote Actually, the alternator will put out whatever the battery and loads require. Unless you are charging a huge battery bank and/or have 200 A load connected to it, it won't put out that much. Given the electrical (and mechanical) losses, the input HP will be whatever are needed to provide the electrical output. The larger alternator will have lower electrical losses, but higher mechanical. All in all, this unit won't present a mechanical load significantly different than a smaller alternator. That's just it. There will definitely be a heavy load on it. When it cranks up every morning it will be seeing a 900AH battery bank ready to take the first 225 amps in bulk mode. This unit must be matched to the appropriate regulator. If you didn't get one with the alternator, the deal may not have been that good. It has the regulator built in. Pretty interesting one too. Even has a battery voltage sense connection. However the regulator does not have a way to change from bulk to absorption to float modes and there is no equalization. The shore power charger can handle the equalization and with my normal use pattern of 50% to 85% charge will rarely need float except at the dock but it would be nice to have optomized bulk and absorption ability. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
#5
posted to rec.boats.electronics
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Can an alternator be to big?
"Peter Albright" wrote in message news:u2fvg.14644$A8.3191@trnddc02... Glen, Have you considered biasing the voltage sense line, to adjust the regulator output voltage? I have been thinking about that. Looks like that would be the only way to control it. The internal regulator is set to maintain 14.4V on the sense line. Boosting the sense line 1.2V would bring the output down to a safe 13.2V float. You could actually put a microprocessor to sense the battery voltage and bias the alternator sense to do everything a "smart" regulator does but that would be more work than I have time for. -- 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 |
#6
posted to rec.boats.electronics
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Can an alternator be to big?
Glenn Ashmore wrote:
"Paul Hovnanian P.E." wrote Actually, the alternator will put out whatever the battery and loads require. Unless you are charging a huge battery bank and/or have 200 A load connected to it, it won't put out that much. Given the electrical (and mechanical) losses, the input HP will be whatever are needed to provide the electrical output. The larger alternator will have lower electrical losses, but higher mechanical. All in all, this unit won't present a mechanical load significantly different than a smaller alternator. That's just it. There will definitely be a heavy load on it. When it cranks up every morning it will be seeing a 900AH battery bank ready to take the first 225 amps in bulk mode. This unit must be matched to the appropriate regulator. If you didn't get one with the alternator, the deal may not have been that good. It has the regulator built in. Pretty interesting one too. Even has a battery voltage sense connection. However the regulator does not have a way to change from bulk to absorption to float modes and there is no equalization. The shore power charger can handle the equalization and with my normal use pattern of 50% to 85% charge will rarely need float except at the dock but it would be nice to have optomized bulk and absorption ability. That could be a problem. If you could tweak the voltage setting down a bit, you could slow down the battery charge rate and the resulting engine load. Petes's suggestion is pretty good. Put in some current sensing on the gen. output and use that to bump the V sense line up as the generator output approaches a setting suitable to your prime mover. You'll need a gain control to set the V bias per amp load and set it so that the system remains stable. -- Paul Hovnanian ------------------------------------------------------------------ Have a pleasant Terran revolution. |
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