On Sun, 29 May 2011 13:27:46 -0400, Home Guy wrote:

" wrote:

Power factor comes into play, mostly when you have a lot of large
motors.

If the motors are fully loaded the PF will be close to one.

In actuality, the larger the motor, the greater will be it's power
factor.

Fractional HP motors (1/8, 1/4, 1/3, 1/2, etc) have low power factors
(37% to 66%).

Motors above a dozen hp have power factors of 85% or better.
Those motors are only better because they are usually sized properly
and are running near their rating. If you lightly load such a motor,
it still can draw a lot of current, but out of phase with the voltage.
Little real power is being used, but lots of VAs. Another way of
looking at it is a lightly loaded motor is acting like an inductor.
The more real mechanical load applied to the motor, the more real
electrical power is required. The motor looks more and more like a
resistor as the power reaches the design limits of the motor.