(mowhoong) writes:

Thanks Sam for your inf. In our plastic moulding company,there is a power
saving unit, we did not use it due to breakdown on contactor inside the
unit, we found 6 nos of very big aluminium electrolytic capacitor,it seem
to be what you have explain improve on the power factor,This unit was
connected to the 440volt 3 phase 300 amp,it was approve by the company
electrical consultant.although now we know the reason for power factor
improvement,but beside this,is there other reason like save on electricity
bill ?
Best Regards.

As an industrial customer, you pay for reactive power. This means that
improving the power factor saves money for you even if the real power
isn't reduced. Residential customers only pay for real power so unless
the power factor is very very poor and IR losses increase significantly,
reducing power factor doesn't do a lot for the electricity bill.

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Sam Goldwasser wrote in message ...
"mowhoong" wrote in message
om...
Sometime ago I walk passed a stall selling power saving unit, it clam
that you can save up to 30% of the electricity bill when you just plug
it into your
house power point. He than demo with a amp meter & a light box(I do
not know how many FL. light they had connected inside the light
box).The amp meter drop from 8A to 4A when they plug it into the power
point, I really don't belive it,but they can show proof infront of
you.Can any person help me to explain ?

A basic fluorescent lamp is usually a highly inductive load. And would
have a lagging power factor and increased current. So, maybe the
box put a capacitor across the line to correct the power factor.

The amps dropped. So what? You aren't paying for amps, you're paying
for watt-hours or true power and that wouldn't be affected significantly.

Go back to that stall with a wattmeter and ask him to show that the
power usage was reduced!