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Old 28-05-2014, 08:27   #1
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NextGen generator output

So I finally got my hands on a scope and put it on our generator output. We have a NextGen 5.5kw, which is a small high-rpm, 2-pole generator using a Kubota engine and Markon generator head that is voltage regulated with a capacitor on the excitation winding.

I always knew the output of these generator heads was dirty, and now I know how much. The following graphs are:
1. Generator waveform with no loads
2. Waveform with 15A resistive load (waterheater)
3. Generator with 15A inductive load (air conditioner)
4. Generator with the 120A heavy transformer-based battery charger that draws 15A

The battery charger cleans up the waveform the best, which I don't understand because it should be an inductive load with a relatively poor power factor.

The manufacturer admits that these are dirty generator heads and tells me that these results are not abnormal.

Please note that everything on board works just fine with this power, although the power drawn is a bit more than on shorepower because of the lower peak voltage of the generator.

Mark
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Old 28-05-2014, 08:36   #2
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Re: NextGen generator output

Interesting.

On my 3.5 KW NextGen which I think has the same Markon gen head, the ammeter needle will bounce an amp or so either side of 12 amps when it is just running the Freedom Charger. It smooths out when I add the water heater load.

Presumably it isn't hurting anything, right?

David
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Old 28-05-2014, 08:43   #3
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Re: NextGen generator output

Presumably. NextGen says it is normal operation. Our Victron system monitor also shows the voltage and amperage moving around average values by a few volts/amps. The frequency stays pretty constant, though.

Mark
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Old 27-07-2014, 02:17   #4
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Re: NextGen generator output

Quote:
Originally Posted by colemj View Post
1. Generator waveform with no loads
2. Waveform with 15A resistive load (waterheater)
3. Generator with 15A inductive load (air conditioner)
4. Generator with the 120A heavy transformer-based battery charger that draws 15A

The battery charger cleans up the waveform the best, which I don't understand because it should be an inductive load with a relatively poor power factor.
I guess that there is no point in achieving a perfect sine curve on a no load situation. Who will run a generator in a no load situation for any length of time?
That type of alternator is cheap and if it requires compromising, it would be normal to tune it for the most common type of load.
4 give the best result. Now if it is for you to find the power factor of that load.
3 air conditioner. It is to be remembered that induction motor power factor is at is best when the motor is fully loaded. For a heat pump it is normally at the start of the cooling cycle and for the fan it is at Full.

Quote:
Originally Posted by djmarchand View Post
On my 3.5 KW NextGen which I think has the same Markon gen head,
the ammeter needle will bounce an amp or so either side of 12 amps when it is just running the Freedom Charger. It smooths out when I add the water heater load.
The freedom charger may produce a fluctuating load that the water heater smooth out. Also the power factor may move toward unity.

Quote:
Originally Posted by colemj View Post
The frequency stays pretty constant, though.
Pretty. What that? 0.1, 1, 2 Hz
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