## Power Factor

## Power Factor

(OP)

I am looking for a chart, table or list of typical power factor values for various industrial devices i.e. lighting, motors, transformers ETC. that can be used in AC Power calculations.

David Baird

dbaird@gemcity.com

EET degree.

Journeyman Electrician.

## RE: Power Factor

Power factor values of AC loads are not the same for all members of a device family. For example an induction motor's power factor is 0.9(fully loaded). However, an another induction motor's can be 0.8 (fully loaded). The exact PF value can only be determined by the device's manual or by measurement. But for rough calculations an average value (for ex. 0.8) can be used. On the other hand, the PF of resistive AC loads (like heaters, incandescent (hot flament) lamps, electrolysis pots etc.) is equal to 1.

In addition, the PF of most of AC devices (including transformers) vary by their loading rate. (for example an induction motor's PF varies between 0.6-0.85 when it's load increases %40 to %100 respectively).

## RE: Power Factor

David Baird

dbaird@gemcity.com

EET degree.

Journeyman Electrician.

## RE: Power Factor

Here some values for induction motors. First value is rated power, second is PS, third is efficiency (%) and the last is power factor.

1.1-1.5-77-0.82

1.5-2-78-0.83

2.2-3-81-0.84

3-4-81-0.84

4-5.5-82-0.84

5.5-7.5-83-0.84

7.5-10-86-0.85

11-15-87-0.86

15-20-87-0.86

18.5-25-88-0.86

22-30-89-0.87

30-40-90-0.87

37-50-90-0.87

45-60-91-0.88

55-75-91-0.88

75-100-91-0.88

90-125-92-0.88

110-160-92-0.88

132-180-92-0.88

160-220-93-0.88

200-270-93-0.88

250-340-93-0.88

315-430-93-0.88

355-483-95-0.89

400-545-96-0.89

that's all for now.

Azmi Demirel

azzmi@elk.itu.edu.tr

Welcome

I am handsome but married :-)

## RE: Power Factor

Power factor is defined as the ration between reactive and apparent power (kvar / kVA).

This is not 'always' the same as the angle between voltage and current. Whenever harmonic currents and voltages are present, how do you define the angle between voltage and current ? For which harmonic ?

Do you use it only for the Fundamental, and what about the harmonics then ...

This problem is source of a lot of discussion right now.

What do you guys think about it ?

## RE: Power Factor

Hi,

I think there is a mistype about the definition of the power factor. The active power is equal to PF times apparent power.

You are right, when the harmonic components get into the account, the calculation of the power factor gets more difficult.

Such as non sinusoidal cases, as you pointed out, the angle between the fundamental components of the current and voltage waveforms are generally used. This approximation results accurate enough to use in any power factor compensation capacitor or wiring calculations.

But if you want to obtain the exact PF value for a non sinusoidal system, i think you can make a few true RMS measurements (for active and apparent powers) or if the waveforms are defined, you can also make some calculations (average value for i(t).v(t) for a period).

Regards

Azmi Demirel

azzmi@elk.itu.edu.tr

Welcome

I am handsome but married :-)

## RE: Power Factor

## RE: Power Factor

Here is what i do with my project. I gather all the data on the motors installed and average out the power factor given at 50% full load. the total power factor is then computed into the kVA from the total connected kW. if you go to www.lifasa.com, there is info on the common power factor used for equipment like lights (sodium, mercury, flourescent, etc). but this would not be the final figure yet. there are many factors else involved such as installation method (cohabitation of differential induced current of cables), switching effect, well being of instllation such as loose connection, etc. however, this is too tedious to compute. the best way to do this is thru stastitical method, i.e., take similiar installation to benchmark. like in my case i benchmark the power factor calculation based on the production capacity/total connected load,etc ratio.

this might not be the most intelligent way, but a smart way.

hope this helps.