Power Factor Improvement and Energy Savings

Apart from helping cables run cooler, that is the purpose of power factor correction!

Apart from cable sizing, power factor correction is one of CR4's favourite topics. Simply enter "power factor correction" into the "Search all of CR4" box to the right.

also 50Hz to 60 Hz (and in one rare case it went upto 400Hz)

A 100 HP three-phase motor, operating at 415 volts with a power factor of 0.85, draws 125 amps. A portion of this current is used to magnetize the motor.

A 22-kvar capacitor(for pf of 0.95) supplied at the motor would provide approximately 20 amps of magnetizing current. Therefore, utilizing the power triangle, only 105 amps are needed from the source.

So, the KWh consumption will reduce...along with your bill.

Thankx spghadei But wont the 22 KVAR capacitor draw current from mains?

The effect will be out-of-phase with the load current. Its purpose is to cancel out the inductive current. Please read-up on power factor correction. Many on-line encyclopediae contain this information.

If considering equipment to effect correction, then it's time to talk to equipment suppliers. Power factor correction is routine stuff, and re-inventing the proverbial wheel is probably a waste of time.

I am very much clear of low p.f. disadvantages. If someone has read my query, its regarding billing in KVAH & KWH. Will there be any cost implications (or wastage) if I do not improve p.f. and I am charged per unit KWH. Please do not consider low p.f. penalty. (say improving p.f. from 0.9 to 0.95)

Let us as you say forget about penalty. Assume you are running a factory.

At a power factor of 0.85 your current is 1000 A then at a power factor of 0.95 you will draw a current of 894A ?

KW = KVA.pf

assuming voltage is constant (for the time being)

I_active = I_tot..pf = 1000 . 0.85 = 850 A

for 0.95 pf

Current = 850 / 0.95 = 894 A

now this reduced current is going to have less losses in your cables ? as well as less voltage drop in cables ? As the voltage drops (assuming it is motor) it draws more current ? hence more copper losses - till it stabilises at a value with quite high losses ?

Though the cables have low resistivity, but they do have it. And this adds up on your transformers and other losses.

With high inductance, even your switches are stressed (braknig.making inductive loads)

This is why, if the load is high, the compensation must be put as near load as possible.

Note here- by improving the pf, it is not only the power supply company that gains but you do it too.

(But do not go to so called over unity ie leading pf zone. it does create problem especially if you have captive generators where this pf will be passed on) in addition to the resonance problems.

BTW- a lot of discussions have already taken place on this aspect, and you have participated in a few too .

Fantastic.... Now can we measure our savings directly using some formula. Or we need to have all cables, busbars etc. etc. specification to calculate it. Any thumb rule?

quote" Can we save energy cost and measure it by improving power factor? I know if my billing is in KVAH and not in KWH, I have to pay as per my power factor condition i.e. More KVAH units at low P.F. and vice versa. What if my average P.F. is 0.85 and I want to improve it to 0.95. I am being charged on KWH. How to calculate the savings ..."

If you are being blled KWH, improving you power factor will not reduce your bill.

First, you are charged for the true power not the apparent power usage. If you correct your power factor you make your machinery more efficient. If you make your equipment more efficient you use less power for the same amount of work. Thus you reduce the cost of your power bill.

Second, we have found that the cost of a reduction from 85% to 95% generally has little payback value. Generally when we realize a 75% PF or greater; it pays to do power factor corrections.

If you have found a cost effective way to correct a power factor of 85% to 95%, now you have got something.

Dear,

You are in Delhi, & As you have told, your billing is on KVAH basis. This is how, industrialists have been either rewarded / penalised by Electricity Co.

If your Average pf is 0.85, there is a scope of reducing your energy bills by 15% by uplifting your mains power factor to unity.

You may use Automatic power factor correction panels with capacitors in the mains.

You may use some fix capacitors in the specific remote feeders.

Design requires some data ....

Nature of load :

CONNECTED Load

Maximum Demand

Transformer Capacity

Heating Load if any :

Lighting load :

Electronics Drives ? how many : rating ?

OP Quote " Can we save energy cost and measure it by improving power factor? I know if my billing is in KVAH and not in KWH, I have to pay as per my power factor condition i.e. More KVAH units at low P.F. and vice versa. What if my average P.F. is 0.85 and I want to improve it to 0.95. I am being charged on KWH. How to calculate the savings "End Quote

Harry's quote "You are in Delhi, & As you have told, your billing is on KVAH basis. "

The post says "I know if my billing was KVAH" etc I am being charged on KWH." If is billing was KVAH he could save some money but it is not. The billing is KWH. There are some very small savings in the system losses but I doubt he would notice it on the bill. No major savings with improved power factor in this situation.

higher pf helps the utility companies in cutting down losses in trasmission . even if one is billed in kw only, he is also billed on maximum demand.please check nyour billing system. the maximum demand becomes higher if pf is low.

Quote "Guest" "the maximum demand becomes higher if pf is low."

ALSO NOT TRUE.

When will you people learn to stop posting when you are essentially guessing!

Low power factor, while it does represent an increased cost of transmission to the utility, will NOT affect your kW demand, BECAUSE IT DOES NOT AFFECT YOUR kW!

Keep repeating this as a mantra in your heads people;

PF does NOT affect kW...

PF does NOT affect kW...

PF does NOT affect kW...

PF does NOT affect kW...

PF does NOT affect kW...

PF does NOT affect kW...

PF does NOT affect kW...

Let me repeat that. Low PF does not affect KW demand. If the customer is billed on KVA, then the KVA is affected by PF. KW demand is not affected by PF.