> We have a 12.5 KW standby generator, and while online and the house air
> conditioner starts up, there is a brief voltage drop with lights
> dimming, but not enough to have to reset clocks, while the carburetted
> gasoline engine's mechanical governor opens the throttle to the demand
> of the new load. Otherwise the generator handles the load fine. Looking
> for a soft start controller or other way to flatten the peak. My HVAC
> contractor indicates there is a kit available that includes a capacitor,
> and he's checking that out with the manufacturer. Apparently the device
> acts like  the capacitor on a capacitor start motor.



Several "Mickey Mouse" ideas.

1. An AC motor running unloaded on the circuit may act as enough of an 
alternator in a load dip to help. This is more usefgul on a 3 phase circuit 
where the motor is a true mechanical rotating system forever 'chasing' the 
rotating AC field. On 1 phase YMMV.

2. Rather than having the switch that starts the air conditioner operate it 
directly you could operate a load softener / stager / ... that reduces the 
impact. One very simple scheme that would definitely work would be to 
incrementally switch in a suitable load at a rate that was slow enough to 
avoid sag problems, thus persuading the genset to throttle up, and then 
enable the air con and back off the dummy load progressively to keep the gen 
set load stable. The load dumping could be simply by timed steps OR could 
monitor the line voltage and act accordingly. Once the aircon is running 
well you remove any remaining dummy load.

The dummy load could be eg a 6 kW water heater element behind a 30A bridge 
with a PWM'd FET. Very easy and simple [tm]. Multiple loads with relay 
switching may be felt to be even easier :-).


  Russell




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