the OP said:OR... Could I just remove the "neutral/ground jumper" in the panel on the generator, to "unbond" them, then ground the generator frame with a rod?
That is ALMOST EXACTLY what you have to do, but do not ground the generator frame with a outside rod. Actually, I think, that is optional, but should be done for lightning strike protection.
By doing so, you have to put the bond back when you use the generator stand-alone, like to operate a power tool when not connected to the house.
JUST REMEMBER ONE THING:
The neutral and Ground of the house has to connect at ONE PLACE only.
With the neutral-ground bond broke in the generator, you are effectively paralleling two grounds which is OK. It also means that a direct lightning strike to the generator outside goes to the ground and not thru the house transfer cable.
Get it?
I am going to disagree a bit with the seperating the generator frame grounding from the generators electrical neutral point. I am assuming that given that you need a 120/240 VAC 60 cycle power source you have a standard american electrical service setup.
Given that at the main power panel in the house it would most likely have all of the electrical common lines and grounding lines tied together it won't matter if they are tied together at the generator either. From the electrical standpoint the generator putting out 120/240 power would be no different than what the utility source transformer puts out of which it and the meter box all will have shared connections from their respective earth ground and common line sets.
Being that the main house panel already shares a physical connection between its earth ground and common lines any secondary connection or lack there of between them at any power input ahead of that is irelavant.
I am guessing that the OP's spark plug wire tachometer is not the least bit accurate and the whole problem is simply a low frequency issue. Grounding or lack there of with the actual generator has nothing to do with it being that there is not a problem when using utility power.
Exactly. If you are getting ~50 Hz readings on the lines with a fair quality digital multimeter the odd are thats the correct reading.
I have used those spark plug wire type tachometers and I don't find them to be all that accurate or reliable.
Given your engine is likely mechanically governed when you set it you should shoot for a 62 - 63 Hz reading at no load. At the full 5500 watt load you should see around 57 - 58 Hz. That's where I aim for when I set up portable generators at.
the OP said:2. Although all of the things I mentioned that I checked for voltage, all were 121 volts, EXCEPT, when I checked the voltage on the circuits running on "generator" in the panel, I touched one probe on the ground bar, and one on the screw on the breaker itself, (only on the generator powered circuits) and got 153 volts! Why would that be?
Yes, mechanically governed. Just a single screw, really easy. Yeah, I'm not even close to that (HZ). Literally, with just one lighting circuit turned on, I was only reading 49-50 HZ at a bulb socket. That's it. When I used that meter on line power I was 59-61HZ. perfect. So the meter is right. I even tried turning the governor up slowly in small increments with the meter on it to see if it would come up. NO DICE. 50HZ...that's it.
rumpfy said:So, for a house, the supply is 240 volt centre tapped 120-0-120 volt, with the centre tap at ground at the consumers main panel.
The supply transformer is 3 phase with each phase delta connected. This means there are 3 neutrals from each supply transformer.
rumphy said:But, for industry, the supply is provided as 120 volt star connected with the star point connected as the neutral to give 120 volt single phase and 208 volt 3 phase.
I guess the mains transformer could be the same design for either application but it would need 6 separate windings each with its own centre tap with 18 terminals for strapping.
Is this how its done?
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