Starting power factor of motor

[urjaengrs]

I have one question regarding motor power factor. I need to calculate the voltage drop in cable at starting of motor. How to calculate motor starting power factor of motor? Does any motor manufacturer mention it? IS there any relationship with running power factor.

Please help me out. In advance thank you.

 

[EddyWirbelstrom]

See Fig. 4.47 of "Industrial Power Systems Handbook" by D Beeman for approximate starting powerfactor of typical squirrrel-cage induction motors.
eg. 100hp ( 75kW ) motor has starting pf of 0.30
If you do not have Beeman, specify motor sizes and I will provide starting powerfactors.

 

[dpc]

0.3 sounds a little on the high side for newer motors. We generally assume 0.2 for motor starting studies, unless we have better data.

 

[Marke]

I agree, the starting power factor can be as low as 0.15, I would use 0.2 as a more realistic figure for modern motors.
Note, as the motor accelerates, the power factor rises reaching a maximum at around 95% full speed. (this is very motor dependent)

Best regards,

Mark Empson

http://www.lmphotonics.com

 

[urjaengrs]

Thank you all.

Actually, I need this starting power factor for motor study calculations. If somebody provide me typical starting power factors for all range of motors, it will be highly appreciable.

In advanse, thank you very much..

 

[dpc]

Yes, that would be convenient. Where have you looked so far?