Strange generator issue

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Todd0x1

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CA
I'm stumped and can't figure this out. I have a 70 kva generator 120/208Y running 18 motorhomes, each on a 30 amp circuit. Voltage on all three phases measures correctly, about 117v at the far end of the line. There is evidence of non-linear loads due to neutral current being higher than what it should be given the phase currents. The energy management systems on some motorhomes are showing voltage in the 130s (even though I measure 117v with a fluke at the same receptacle).

Only thing I can think of is harmonic distortion causing false high voltage readings on the motorhome EMS where the DMM filters it out.

any ideas?
 
I wonder if the frequency may be off? Might affect the sensitivity of the energy management, I believe they also monitor frequency due to optional on board generator power
 
hillbilly1 said:
I wonder if the frequency may be off? Might affect the sensitivity of the energy management, I believe they also monitor frequency due to optional on board generator power
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frequency is perfect. These are newer generators with electronic controls.
 
ptonsparky said:
Try shifting them so the loads are more even across the phases.

Is this suddenly a new problem?
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Been doing this same setup for several years, first time I have this issue. Only differences are in the past I used a same size generator but it had an oversized alternator (lower source impedance = less thd right?) and some of the motorhomes are newer this time.

As far as shifting loads, the outlets are spread evenly (6 per phase) but the load on each outlet is constantly changing -can't do anything about that.
 
So I just got back from moving 1/3 of the connected load to another generator. This other generator has more sophisticated controls and it displays power factor. I set the generator voltage a little low so the motorhomes wouldn't alarm out on high voltage. 116v. Turned the load on and after a bit (as electronics booted up or whatever) I see phase A = 116v phase B = 116v, phase C = 120v. Then i switch to the PF screen. The readings were constantly changing but phase A was in the 90s lag, phase B was in the 90s lag, and phase C was in the low 60s lag, even dipped down into the 50s once. So it appears that when the power factor is really bad some instruments (such as the motorhome systems, and the deepsea controller on the generator) read a higher than RMS voltage. Interesting.

I need to learn about PFC and see if theres a solution out there for future use.

I also need a power quality analyzer.
 
Maybe some of the newer MH’s has inverter A/C’s which are affecting the power factor? (Heat pump mode) My TT is not that old, but I swapped out the A/C to the inverter style, much quieter! Got another one to do for a customer tomorrow if it’s not raining. Don’t have anything to check power quality. Might be on my tool list for next year. LOL!
 
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