power saving by capacitor

Zero. Improved power factor does not change the KWH used by the motor. If will decrease the Demand Charge if you are being billed for demand.

Actually the kW demand will also not be affected, for the same reason. If the kVARh or kVA is recorded, then a charge might be possible from the power supplier.

Zero is still the correct answer to his question.

Regards, CJM

Quote CJ McGill "Actually the kW demand will also not be affected, for the same reason."

CJ, Thanks for catching that for me. I said "It will decrease the Demand Charge if you are being billed for demand."

I should have said "It will decrease the KVA Demand Charge if you are being billed for KVA demand." It will not reduce the KW demand Charge as CJ pointed out.

Additionaly, improved PF will also reduce stress on the circuit components such as switch, breaker/contactor etc, as the current thru these components will be reduced.

How much power will be saved by 60kvar power capacitor unit for improving power factor from 0.85 to .95 200kw s.c.i.m.motor.

None. This is a mis-conception. What the capacitor does is to stop the apparent power being metered and charged and to decrease cable size. Modern electronic meters may overcome this metering anyway. The other factor is that the current is out of phase with the voltage. Cable heating is caused by I²R so cables must be larger to dissipate the extra heat. The power does not change. Beware of snake-oil salesmen.

Very little. The capacitance will reduce cable losses. It will not affect the power consumed by the motor.

The question arises as to the tariff being charged for the electricity. If the tariff is based on kVA, then savings might be made by installing power factor correction [PFC].

If the distribution system is running close to maximum current, then adding PFC might be a better investment than uprating sections or all of the distribution system.

It all depends upon local circumstances, which cannot be seen from here.

The Losses in the cable and Transformer will reduce by 20%

Zero saving

Is it me, or does this seem more like a homework question? Oh well, since nobody else brought this up it must be me.

Paneer

Would you show me how you came up with the 20% savings.

It can only be correct where the current from the specific device are not aggregated with currents from other sources. In addition, it is only correct for the resistive part of the loss.

Essentially the power factor is a measure of the ratio of RMS current to what would be needed for the same power in an ideal resistor. So the relative resistive losses in the wiring at 0.95 power factor would be (0.85/0.95)², or 0.800554 - a reduction of about 20%. Even that is reduction relative to the losses, not to the power used. Once the current is added to other currents of similar magnitudes the effect of changing the phase/power-factor of just one of the contributors becomes much smaller.

BTW, a major reason for the difference in utility costs is the size of the wiring that needs to be provided to avoid overheating etc. In principle that means that the additional cost overhead will depend on whether the equipment is in use at times of peak system loading. (Whether this is reflected in charges is a different matter)

I like that answer, very well put together GA for you.

yeah. i'm still scratching my head about that 20% savings. elaborate please.

Perhaps this will put the 20% in perspective.

The resistive I²R (heat) losses are the only thing improved. Since this is a very minor factor in a properly designed circuit with properly sized conductors, a 20% improvement of a very minor factor then results in a very very minor improvement compared to the power drawn by the load, which stays the same and is not affected.

Since the power company's distribution system has certain limits and is not always up to the Amp demands of increasing numbers of loads, they are the ones requiring better PF resulting in lower amps, or possibly pay some fee to cover the cost of improving their system to meet the demands.

The consumer's individual load is not where any significant I²R savings will occur with improved PF.

Regards, CJM