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 Post subject: Generator issues
PostPosted: Mon Jan 22, 2018 10:15 pm 
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I hope this in in the correct section! Briefly I recently bought a small diesel generator yanmar l48 engine. The alternator has Hartlepool uk on it but I cant read the label no plate on it. There was no power being produced and I checked the capacitor which had burst so I replaced it with one with the same numbers. It produces power, 252 volts at 3000 rpm. I lowered the engine speed it's now producing 230 volts at 2850 rpm. I think the frequency will be off ? Is there any way to sort this out? Thanks and sorry for the long post.


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 Post subject: Re: Generator issues
PostPosted: Tue Jan 23, 2018 1:26 am 
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no expert
but suspect iff you put any sort off load on it you will be a bit low on volts
253v is the upper level with mains anyway its something like plus 10-6%from 230v

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 Post subject: Re: Generator issues
PostPosted: Tue Jan 23, 2018 5:19 am 
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For those that don't know, the electricity frequency in the U.K. should be 50HZ, in America it is 60HZ, if something is run at the wrong frequency it can damage it. The frequency is in relation to the speed of rotation, hence PaulK's question. It has nothing to do with voltage and loading.

PaulK, I would say that in short the answer is no, since the frequency is as you know in relation to the rotational speed, short of putting an oscilloscope on it you will not know the actual frequency, so all I can suggest is be careful with anything you run form your generator that has a motor, such as pumps, drills or compressors, they should work, but running at the wrong frequency they will run slower or faster (Depending on the actual frequency) I would say slower, in turn drawing more current, overheating the device.

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 Post subject: Re: Generator issues
PostPosted: Tue Jan 23, 2018 6:36 am 
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3000 rpm divided by 60 = 50 Hz with two pole generator, so should be 3000 rpm. Your now running at 47.5 Hz so needs speeding up.

There are many ways to adjust voltage, it is common to use two methods at once, so one sets the no load voltage the other sets the on load voltage and the generator will only have the correct voltage at two current outputs, it is just some where near between the two.

The other is to use an AVR an electronic unit to adjust output, and the third method is to convert the output to DC and then turn it back to AC so the motor can run at a variable speed.

The drop in speed no load to full load is called droop, and with some units this is used to synchronise the outputs of multi generators so each generator takes its share of the load, but smaller generators tend to use DC and an inverter to parallel up.

The point being there are many ways to control a generators output, so one would need a circuit diagram at least to know how to adjust your generators output. But 252 volts is within the range for a UK supply so why try dropping it? UK voltage is 230 volt +10% -6% so 216.2 to 253 volt is the range.


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 Post subject: Re: Generator issues
PostPosted: Tue Jan 23, 2018 10:36 pm 
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Is 252 volts the no load voltage? It's probably set high, so if the voltage drops a bit on load it's still within limits. As Ericmark says, why change it? 252 volts is perfectly fine.

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