Hi,

Both Charles Wing and Nigel Calder allude to connecting the neutral
and ground wire of AC generators at the generator. Both authors also
show alternator generators with a centre tap at 0v and the other two
conductors at +60/120v and -60/120v (giving 120 and 240v
respectively). The 0v centre tap I think is connected to ground, but
is one of the conductor wires really connected to the ground??? Both
authors have produced diagrams with no ground/conductor connection
shown. It seems a little odd - grateful for clarification.

TVMIA

"Rob" wrote in message
om...
Hi,

Both Charles Wing and Nigel Calder allude to connecting the neutral
and ground wire of AC generators at the generator. Both authors also
show alternator generators with a centre tap at 0v and the other two
conductors at +60/120v and -60/120v (giving 120 and 240v
respectively). The 0v centre tap I think is connected to ground, but
is one of the conductor wires really connected to the ground??? Both
authors have produced diagrams with no ground/conductor connection
shown. It seems a little odd - grateful for clarification.

TVMIA

Yeah like " I can't be bothered reading books or studying, would someone
please tell me in less than 25 words all about electricity. In particular AC
theory which can't be all that complicated since there are so many
electricians doing it. Not like it's difficult like real technicians who fix
TV's and things"

--
Regards ............... Rheilly Phoull

Yeah like " I can't be bothered reading books or studying, would someone
please tell me in less than 25 words all about electricity. In particular AC
theory which can't be all that complicated since there are so many
electricians doing it. Not like it's difficult like real technicians who fix
TV's and things"

A particularly useful contribution - and I have been reading the books
- hence the question. If you have not got anything worthwile to say
that adds to the discussion, then don't bother cluttering up the
listing with your drivel.

On 26 Dec 2003 01:19:31 -0800, (Rob) wrote:

Hi,

Both Charles Wing and Nigel Calder allude to connecting the neutral
and ground wire of AC generators at the generator. Both authors also
show alternator generators with a centre tap at 0v and the other two
conductors at +60/120v and -60/120v (giving 120 and 240v
respectively). The 0v centre tap I think is connected to ground, but
is one of the conductor wires really connected to the ground??? Both
authors have produced diagrams with no ground/conductor connection
shown. It seems a little odd - grateful for clarification.

TVMIA

120/240V gensets are, at least in the USA, set up like USA's
antiquated, unstandard AC power system, just like Tesla created it.

120V-------Neutral---------120V

The two 120V are out of phase (180 degrees), so if you connect from
120 to 120 you get 240 VAC to power big items. Our National Electric
Code requires the Neutral (center tap of the transformer secondary out
on the street) be a separate wire to carry the current from ground,
even though they are both connected together at the pole. There is no
60-0-60 power, here.

However, on ships, to reduce the voltage to ground reducing shock
hazards on 120V power systems, there IS a 60-0-60 system with a
center-tap-grounded power system. I used to serve on old Navy ships
that had this system. Not sure if they still use it on new ships,
now.

So, any 120/240 genset targeted at the US/Canadian market will have a
4-wire system, two 120V phases 180 degrees out of phase, a neutral
wire to carry the current to the center-tapped windings and a separate
ground which is the case of the genset and should be hooked to the
center tap of the genset's windings at the genset ONLY.

Hope this helps

Larry W4CSC

NNNN

On Fri, 26 Dec 2003 14:09:27 GMT, Larry W4CSC wrote:

On 26 Dec 2003 01:19:31 -0800, (Rob) wrote:

Hi,

Both Charles Wing and Nigel Calder allude to connecting the neutral
and ground wire of AC generators at the generator. Both authors also
show alternator generators with a centre tap at 0v and the other two
conductors at +60/120v and -60/120v (giving 120 and 240v
respectively). The 0v centre tap I think is connected to ground, but
is one of the conductor wires really connected to the ground??? Both
authors have produced diagrams with no ground/conductor connection
shown. It seems a little odd - grateful for clarification.

TVMIA

120/240V gensets are, at least in the USA, set up like USA's
antiquated, unstandard AC power system, just like Tesla created it.

120V-------Neutral---------120V

The two 120V are out of phase (180 degrees), so if you connect from
120 to 120 you get 240 VAC to power big items. Our National Electric
Code requires the Neutral (center tap of the transformer secondary out
on the street) be a separate wire to carry the current from ground,
even though they are both connected together at the pole. There is no
60-0-60 power, here.

However, on ships, to reduce the voltage to ground reducing shock
hazards on 120V power systems, there IS a 60-0-60 system with a
center-tap-grounded power system. I used to serve on old Navy ships
that had this system. Not sure if they still use it on new ships,
now.

So, any 120/240 genset targeted at the US/Canadian market will have a
4-wire system, two 120V phases 180 degrees out of phase, a neutral
wire to carry the current to the center-tapped windings and a separate
ground which is the case of the genset and should be hooked to the
center tap of the genset's windings at the genset ONLY.

Hope this helps

Larry W4CSC

NNNN

Larry,

Being totally unfamiliar with naval systems, the question Rob asked still
remains: Is the neutral (in a 60 - 0 - 60 system) connected to one of the
60 volt legs? Is it still coded white? I'm assuming that ground is always
connected to frame or earth ground in any system.
--

Larry
email is rapp at lmr dot com

On Sat, 27 Dec 2003 18:15:16 GMT, Larry wrote:


Being totally unfamiliar with naval systems, the question Rob asked still
remains: Is the neutral (in a 60 - 0 - 60 system) connected to one of the
60 volt legs? Is it still coded white? I'm assuming that ground is always
connected to frame or earth ground in any system.

I'm sorry but I really don't remember. The last ship I was on with
this was USS Everglades (AD-24) completed in 1952. I was on her from
1966-1969 and I'm WAY too old to remember details back THAT far,
now....

But, as I remember doing some wiring in our calibration lab, I don't
think there was a "neutral" in that system. The 120VAC was from one
wire to another and I don't think the center tap of it was connected
to anything but ship's ground, as we didn't use the 60VAC for anything
to that center tap.

Many ships have ungrounded systems, with ground fault monitoring. Single
phase panels are used (without the neutral bus), or three phase panels (120
volt delta). All circuits use 2 pole breakers. Common ground monitor is
lights from phase to ground, if the light is out the phase is grounded.

Pete Albright,
Tampa, FL

"Larry W4CSC" wrote in message
...
On Sat, 27 Dec 2003 18:15:16 GMT, Larry wrote:


Being totally unfamiliar with naval systems, the question Rob asked
still
remains: Is the neutral (in a 60 - 0 - 60 system) connected to one of
the
60 volt legs? Is it still coded white? I'm assuming that ground is
always
connected to frame or earth ground in any system.

I'm sorry but I really don't remember. The last ship I was on with
this was USS Everglades (AD-24) completed in 1952. I was on her from
1966-1969 and I'm WAY too old to remember details back THAT far,
now....

But, as I remember doing some wiring in our calibration lab, I don't
think there was a "neutral" in that system. The 120VAC was from one
wire to another and I don't think the center tap of it was connected
to anything but ship's ground, as we didn't use the 60VAC for anything
to that center tap.

In article ,
"PeteAlbright" wrote:

Many ships have ungrounded systems, with ground fault monitoring. Single
phase panels are used (without the neutral bus), or three phase panels (120
volt delta). All circuits use 2 pole breakers. Common ground monitor is
lights from phase to ground, if the light is out the phase is grounded.

Pete Albright,
Tampa, FL

"Larry W4CSC" wrote in message
...
On Sat, 27 Dec 2003 18:15:16 GMT, Larry wrote:


Being totally unfamiliar with naval systems, the question Rob asked
still
remains: Is the neutral (in a 60 - 0 - 60 system) connected to one of
the
60 volt legs? Is it still coded white? I'm assuming that ground is
always
connected to frame or earth ground in any system.

I'm sorry but I really don't remember. The last ship I was on with
this was USS Everglades (AD-24) completed in 1952. I was on her from
1966-1969 and I'm WAY too old to remember details back THAT far,
now....

But, as I remember doing some wiring in our calibration lab, I don't
think there was a "neutral" in that system. The 120VAC was from one
wire to another and I don't think the center tap of it was connected
to anything but ship's ground, as we didn't use the 60VAC for anything
to that center tap.






Pete is correct in that some on board wiring deletes the netral to earth
bonding altogether. In this situation you loose the fault current
protection generated when there is a fault from active to conductive
case of equipment. In this instance it is absolutely imperative to have
Residual Current Devices (RCD's) or GFI in NA parlance both on the shore
power inlet and the onboard generator. I just did an electrical survey
on a boat where this was the case. BTW downunder we have 240/408
single/3 phase 50 Hz systems.

John Proctor

--
John VK3JP

On Sun, 28 Dec 2003 01:13:43 GMT, "PeteAlbright"
wrote:

Many ships have ungrounded systems, with ground fault monitoring. Single
phase panels are used (without the neutral bus), or three phase panels (120
volt delta). All circuits use 2 pole breakers. Common ground monitor is
lights from phase to ground, if the light is out the phase is grounded.

Pete Albright,
Tampa, FL

Now that you mention it I do think I remember a light on our
knife-switch/screw-in fuse panel (black bakelite with wooden safety
leaning bar), that alerted you to any current to the deck, indicating
a fault.

The cal lab had a Detroit Diesel, naturally-aspirated 6-71 2-stroke
diesel driving a DC generator that originally powered the stern gun
mount and director, which was removed when the disasterous DASH
anti-sub helicopter was installed. The DC powered a big
motor-alternator through a separate manual panel to create 60 Hz, 3
phase, 440 VAC that was fed to a bank of transformers buzzing away in
the cal lab to keep us awake at night. All our Edison Lights were run
directly from 110 VDC from the DC panel through a couple of knife
switches....as Edison intended.

The whole ship would go dark because of the Electical gang's
incompetence a few times per voyage. The separately-powered cal lab
shone like a beacon in the dark, then....(c;

Larry ET1
Shop 67B, Calibration Lab
USS Everglades (AD-24)
Charleston, SC (1966-1969)

Electricians were not allowed to have keys to OUR generator
room.....hee hee. They never gave us keys to THEIR generator rooms,
after all. It was only fair.

In the Med, we used to turn the motor speed on the alternator down and
run the cal lab on 50 Hz to keep the TV picture from pulsing at 10 Hz
from the differences in scan frequencies and power supply hum....(c;
I still have reel-to-reel tapes with 50 hz hum on them!

Larry W4CSC wrote:

However, on ships, to reduce the voltage to ground reducing shock
hazards on 120V power systems, there IS a 60-0-60 system with a
center-tap-grounded power system. I used to serve on old Navy ships
that had this system. Not sure if they still use it on new ships,
now.

There was never a "60-0-60 system" on ships. Nearly every ship generates
3-phase power and for hotel services requiring 120VAC the phase
transformers are wired in wye-delta providing 3 conductors each of 120
volts between any two conductors. The voltage measured to ground would
be either about 87 volts or 70 volts depending on the phase which is
measured against the ship's ground.

When 120/208 power is required the phase transformers are wired in
delta-wye with a 4th neutral conductor connected to physical ground. Any
conductor measured to ground would deliver 120 volts single phase. The
voltage between conductors is 208 volts 3-phase. This is not commonly
supplied to "hotel" services as it is preferable to reduce shock hazard
via the lack of a grounded neutral and to avoid using the hull as a
current carrying ground.

Rick