? about amps.

Since power factor is involved (true power....watts, vs apparent power....measurement of volts and amps) it usually takes more than the VxA=741 to equal what the motor is using.(PF is usually lagging due to inductive load.....hence running capacitors are added to motors to bring it back up) and then there is the effeciency of the system...motor, pulley's, gears, belts, etc.

Power companies like PF at 1. If it really gets whacko they send you a lot of power but your meter doesn't recognize it and they loose $$$.

HTH

Mark

--->Paul

If you come across one of those motors with a power factor of greater than 1, can you send it my way? I'm working on a perpetual motion machine, but the one part I can't seem to find is a 1.1 PF motor. ;=)

As buick 'n' deere correctly stated, power factor is always less than or equal to 1. Capacitive loads cancel out inductive loads.

I was talking about power factor in a general sense. I agree inductive loads such as motors will not have a power factor greater than 1. My area is in power/high voltage so to me the standpoint is to look at a customers load from an overall standpoint. Although people don't have capacitive loads overall it is possible to create a cpapcitive load if you wanted. (Although that would tend to make the system unstable).

So if a motor had a PF of 0.8 and the VA was 1000. The watts used would be 800 BUT the entire electrical system has to be still sized for 1000VA. Or sized for 1000W as if this load happened to have been resisitive with a PF of 1.0 . DC equipment is a direct calculation as 120VDC and 7 amp would be 840 watts.

The actual value of the power factor will not be over 1. It would be some decimal either leading or lagging, depending on type of load.

I thought electric motors with higher PF (closer to 1.0) were better & used less watts - at least at startup. But using your calculations it would appear a lower PF results in less VA or watts being used for the same hp?????

From the first explination I thought perhaps it is measuring start-up load. But doesn't seem to. That would be a factor in the original question as well, not just 'running' watts of an electric motor....

--->Paul

What power factor IS is the cosine of phase angle between the AC voltage and current applied to a load. If you remember your high school trig, you'll know that the cosine of anything has to be between -1 and +1. However, to have a negative power factor the current would have to be leading or lagging the voltage by greater than 90 degrees, which doesn't happen in the real world.

For a purely resistive load, the current and voltage are perfectly in phase, so the power factor is unity. For a pure inductor, current lags voltage by 90 degrees, while it leads voltage by 90 degrees for a pure capacitor. You can adjust the power factor of an inductive load (such as a motor) by adding capacitance.

If a load has a power factor of less than one, that doesn't mean it's inefficient. It just means that the product of voltage and current is less than the power delivered to the load, since voltage and current are out of phase. Inductors and capacitors are just storage devices; they absorb energy from the grid, then send it right back, 120 times per second.

So what's the relationship between power factor and efficiency? For the load itself, none. However, because the power transmission lines have to carry extra current that isn't producing any power, there are power losses in the transmission line. That's why power companies don't like low power factors. And that's also why generators and transformers are rated in volt-amps, not watts.