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Old 18-01-2020, 13:58   #1
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High frequency on Northern lights M753K

I am stumped, my northern lights M753K, 8kw, for some reason has really high frequency output, anywhere from 120hz to 180hz high. The voltage coming out is spot on at 120volts on each leg. 220volt unit, my panel is split and each gets it's own leg of 120volts. At first I thought my gauge on the panel was faulty but I tested with my volt meter and compared the frequency between shore power, 60hz, and the generator legs. There are no fluctuations in engine speed. No wiring on the generator side has been modified or replaced, all connections appear to be tight and secured.

Any thoughts?
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Old 18-01-2020, 14:21   #2
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Re: High frequency on Northern lights M753K

Generator output frequency is a function of generator speed. While monitoring frequency, adjust the genset speed down. Unloaded freq should be about 62 Hz. It will sag into spec when a load is placed on it
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Old 18-01-2020, 14:31   #3
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Re: High frequency on Northern lights M753K

While engine speed DOES control frequency, I think something else is going on here...

I think you'd notice if the engine speed was DOUBLE its normal value up around 3000 RPM instead of 1800...
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Old 18-01-2020, 14:42   #4
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Re: High frequency on Northern lights M753K

Try putting a resistive load on it like a heater or hair drier, coffee pot etc and see if it settles down.
Only way to change frequency that I know of is RPM, and that’s obviously not it, but maybe somehow the meter is reading noise etc as frequency
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Old 18-01-2020, 14:48   #5
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Re: High frequency on Northern lights M753K

@billknny
I read the symptoms wat too fast ��- you are absolutely correct, something else must be going on. On the other hand AFAIK, the only way to adjust freq is to adjust genset speed.

OP:
Can you determine what the genset speed is?
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Old 19-01-2020, 13:32   #6
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Re: High frequency on Northern lights M753K

- All good comments.
- Many inexpensive multi meters are not very good at reading Hz. accurately so also check with a good ( ( $800+ ) meter as well if possible.
- Assuming that the meter is ok then the likely cause of your symptoms is probably a failed main control board or a wiring issue.
- PS, your generator should be single phase, 120/240 volts output, if it is producing 120/220 volts than there is something really peculiar going on.
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Old 19-01-2020, 14:42   #7
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Re: High frequency on Northern lights M753K

Quote:
Originally Posted by Tiberon12 View Post
I am stumped, my northern lights M753K, 8kw, for some reason has really high frequency output, anywhere from 120hz to 180hz high. The voltage coming out is spot on at 120volts on each leg. 220volt unit, my panel is split and each gets it's own leg of 120volts. At first I thought my gauge on the panel was faulty but I tested with my volt meter and compared the frequency between shore power, 60hz, and the generator legs. There are no fluctuations in engine speed. No wiring on the generator side has been modified or replaced, all connections appear to be tight and secured.

Any thoughts?
I'd bet you have a meter problem. Run a fan with a synchronous motor see if the blades fly off.
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Old 12-02-2020, 21:11   #8
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Re: High frequency on Northern lights M753K

Your frequency display is bad. You would notice the increase in RPM by the sound of the generator. 2-3 times higher RPMs on the diesel is very noticeable.
Im not sure why cheapo multimeter in a Hz scale would not show you the frequency.

A bit more money would plot you a waveform.



https://www.amazon.com/Oscilloscope-...53671078&psc=1
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Old 12-02-2020, 23:01   #9
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Re: High frequency on Northern lights M753K

Quote:
Originally Posted by Tiberon12 View Post
I am stumped, my northern lights M753K, 8kw, for some reason has really high frequency output, anywhere from 120hz to 180hz high. The voltage coming out is spot on at 120volts on each leg. 220volt unit, my panel is split and each gets it's own leg of 120volts. At first I thought my gauge on the panel was faulty but I tested with my volt meter and compared the frequency between shore power, 60hz, and the generator legs. There are no fluctuations in engine speed. No wiring on the generator side has been modified or replaced, all connections appear to be tight and secured.



Any thoughts?


A64pilotís suggestion in post 4 is a sound idea idea, could simply be resonance.
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