# Single Phase Generator Load



## heliospro (Dec 19, 2017)

I have a new 10K Perkins diesel generator which is being used in an off-grid solar system. Since the loads are 120V only, I wired only L1 and neutral to the load (about 20 amps) and left the other leg unused for the time being. With that load, the generator voltage goes up to 130V on the loaded leg and 256V between phases. Frequency goes to about 63. With no load, everything is normal. Is it possible that only 20 amps is enough to unbalance a generator this size and create this situation?


----------



## KRE (Nov 29, 2011)

Short answer is yes, as you can only pull 5kw of unity power (not reactive) from each leg. Wire the other leg in as well an split the 120 load.


----------



## heliospro (Dec 19, 2017)

So, 20 amps is only 2.4 kW. I will wire the gen for 120 and see if this resolves it, but I am curious why less than 25% capacity of the unit is enough to create an issue. Thanks for the response!


----------



## KRE (Nov 29, 2011)

heliospro said:


> So, 20 amps is only 2.4 kW. I will wire the gen for 120 and see if this resolves it, but I am curious why less than 25% capacity of the unit is enough to create an issue. Thanks for the response!


Is this a 12 or 3 lead alternator? Your imbalance error is much greater do to the fact your not using 1 set of the winding's. If you were using both sets an had a 20-25% imbalance the voltage difference would be much smaller. Your imbalance as stated is approaching 50% that is why you see the greater difference.


----------



## heliospro (Dec 19, 2017)

It's a four-lead alternator according to the specs. Again, I'll just wire it for 120 which is cheaper than a transformer. Thanks!


----------



## KRE (Nov 29, 2011)

Just FYI

A 4 lead stator is a Y wound 3 phase. A 3 wire stator is either a 3 phase delta only, which is very, very rare in such a small machine, or it's a single phase only machine, which is what I suspect your is. The 4th wire in a single phase unit is always the ground which is not wound in the stator wiring.
6, 9 an 12 lead will make most any voltage that can be used either in delta or Y application.


----------

