Power Factor

[jayaeros]

Hi,

I would like seek clarification on the three phase power calculation.

Using the clamp meter, i obtained the VL = 415 V and the IL=10.7 A. On the other hand, my power meter indicating a reading of 4750 W.

Thus, my power factor = 4750/ (1.732x415x10.7)
= 0.62

Why is the power factor is too low? From my understanding, the advisable power factor is approximately 0.9?

Is this low power factor value is due to problem of the compressor (manufacturer fault) or bad electricity efficiency on my side?

To be honest, i understand the mathematical meaning of power factor (high pf, means low amps draws and etc), but i cant get the physical sense of it.

Please help.

Regards,
jaya

[Sandro Baptista]

Maybe the motor is very large for the compressor working in the present regimen or/and the compressor is working at partial load. If the electrical motor is working almost unload (low resistant binary of the compressor) then the reactive power due to electric indutance will be more "weighted" compared with the active power (this last should be the last you measured.

1.732x415x10.7 is the apparent power

[Yuri B.]

Why is the power factor is too low? From my understanding, the advisable power factor is approximately 0.9?

You should not bother about PF (in your net) as long as you dont pay for it (then you take measures to keep it in norm).
Usually it is small induction motors, which are overfluxed, and have lower PF (and low efficiency).
When unloaded, induction motors have lower PF, as previous poster said, shaft load incresing, PF rises (PF from nameplates refers to full load).
If that measurement were obtained at full load, then your motor is one of low efficiency (probably, some old design).

[jayaeros]

Hi,

The measurements are obtained at the full load of the cooling capacity and the compressor is a brand new- Copeland ZR81KC TFD 522. I am wondering on what is the full load of the compressor. The power factor is not stated on the name plate. Only the voltage (380-420 V), max ampere Ampere (15A), LRA I block (90.-101.0), N (2900 min-1), Flow rate (19.23 m3/h) are stated on the name plate.
Does this mean that compressor is excessively oversized as the operating current is 11 A and the maxim amp as in the name plate is 15 A.

Thank you

[Yuri B.]

Why be so preconcerned with p.f.? Let it be what it is as long as one is not required to pay the bills for reactive power.