low power factor 2

[ricjorge]

We have a 1000 kw, 400v, 50 hz generator working for commissioning. Since beginning, we experience low power factor when load is less, typically .45, but when the compressor motor, rated 250 kw, started running, power factor increases to .81. I suggested the cause can be attributed to the temporary feeder cables which at several points where bundled together, instead of usual practice of segregation. Could there be any other reason for this?

 

[dpc]

Power factor is a function of the load, not the feeder cables.

At low load, motors have low power factors. Power factor goes up as the motor load increases.

The grouping of the feeder conductor may have a very slight impact on the inductance of the feeder, but tighter bundling would actual lower the inductance. But these are third or fourth order effects when compared with impact of the load power factor.

"An 'expert' is someone who has made every possible mistake in a very narrow field of study." -- Edward Teller

 

[rbulsara]

There is nothing wrong with your system.

 

[electricpete]

I agree with the above. As a starting point to understand low generator power factor at low load you need to consider what is connected to the system at low load and what kind of power is each piece of distribution and utilization equipment consuming. Transformers at no load draw vars for magnetizing current. Also... are there real and reactive power interchanged with the grid.

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[waross]

Put some duct tape over the power factor meter so no-one can read it and everything will be fine.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[ricjorge]

Thanks for the information, and I believe electricpete had given me an idea since our only load without the compressor motor is the UPS, which is actually seen as a transformer running at very low load at the moment, since only a few circuits had been energized.