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Generators & Electric Motors General Discussion Antique Generators and Old Electric Motors: Questions and answers about restoring and showing old power generation systems.

Generators & Electric Motors General Discussion

Generator voltage parameters


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  #1  
Old 11-28-2018, 04:02:25 PM
opus opus is offline
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Default Generator voltage parameters

What are acceptable voltage parameters for a 120v generator? 110-125?
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Old 11-28-2018, 05:41:20 PM
Railroads Railroads is offline
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Default Re: Generator voltage parameters

Depends on the type of generator. Most of the time we adjust for frequency and the voltage just happens to fall in place. Frequency no load should be 60-62HZ. Or 50-52HZ depending on the location. America or Europe.

On generators with no voltage regulator the voltages could be as high as 135 volts or 255v once engine rpm is adjusted for correct frequency. Frequency is more critical for most motor and transformer loads. Too low a frequency and they can run too slow and burn up for induction motors. Transformers can draw too much current for magnetizing the steel and run hot. Too high a frequency is just as bad and can cause issues in transformers and cause induction motors to run above rated RPM.

If the generator has a voltage regulator adjust for frequency via engine RPM and then tune the voltage regulator for correct voltage output. Only higher end sets are so equipped most of the time.

Robert
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Old 11-28-2018, 09:16:06 PM
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Default Re: Generator voltage parameters

My apologies, my question was vague. This is just a general emergency type home generator. I've got it set pretty tight I think. My no load is 123-124v and load volts is where it needs to be. I had nothing to measure hz today, just voltage.
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Old 11-28-2018, 09:28:55 PM
Wayne 440 Wayne 440 is offline
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Default Re: Generator voltage parameters

Here is the industry standard for utilities. Should give you an idea of what to try for.

https://www.spgsamerica.com/upload/d..._green_bar.pdf
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Old 11-28-2018, 09:31:14 PM
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Default Re: Generator voltage parameters

Great. I didnt know there was that much of an "allowable" swing.
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Old 11-29-2018, 07:44:54 AM
I like oldstuff I like oldstuff is offline
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Default Re: Generator voltage parameters

Quote:
Originally Posted by opus View Post
My apologies, my question was vague. This is just a general emergency type home generator. I've got it set pretty tight I think. My no load is 123-124v and load volts is where it needs to be. I had nothing to measure hz today, just voltage.
Go to a big box store and buy a kill a watt meter for about $25. It's a handy tool to set freq and to see what loads you are using.
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Old 11-29-2018, 11:54:55 AM
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Default Re: Generator voltage parameters

I have a couple at home. I was just curious to see what parameters were acceptable.
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Old 11-29-2018, 01:34:05 PM
Kevin K Kevin K is offline
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Default Re: Generator voltage parameters

For the older Onan saturated pole generators, 130 to 110 volts no load to full load is in the ball park. Most times you can do a bit better, but not by much. Not great voltage regulation, but the price you pay for simplicity and no expensive voltage regulator to fail. The problem is not so much the voltage at the generator, but the voltage at the load. With no regulator to maintain 120 volts at the generator line loss becomes more of a factor. For example, using 100 feet of #12 between the generator and load with a 20 amp current, the voltage drop is about 6.3 volts. If the generator output voltage was 110 volts at a 20 amp current draw that would give you 103.7 volts at the load, which is getting marginal. The same 20 amp draw using a #14 extension cord would give you a 10 volt drop, turning 110 volts at the generator to 100 volts at the load.

A handy voltage drop calculator:
https://www.calculator.net/voltage-d...lculator.html?
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Old 11-29-2018, 02:08:55 PM
opus opus is offline
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Default Re: Generator voltage parameters

For this one it is this: https://youtu.be/-gsQBKDOE2Q

And its wired into the meter, so no real drop. Its a 10k head. There is a idiot gauge on it. No load it is at the top limit of the green.

I'll need to get my kill-a-watt to check it out to be sure but I was curious nonetheless.
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