Someone can help me about Power factor of Single Phase motors?

Question

What is the power factor of single phase capacitor start motor while running under load or without load. Some motors have capacitor permanantly connected in series winding. What power factor of these motors?

Answer 1

Yes, there is a power factor for motors. For any AC fed electrical device, unless it is purely resistive (which motor is not), there are power factors. Because motors are inductive, it has reactance components. By having reactive components, the rise of voltage is not in synch with the current - which causes apparent power consumption differ from effective power consumption. This is the power factor.

Exactly what it is for your motor, there is no way for me to tell.

The capacitor is used (required) for AC motors for single phase to create a 90 degree off phase signal, so the second winding develops magneticism at the different timing from the first. Without this phase differential, the motor won't turn.

On 3 phase motors, this is not necessary, as you already have 3 phase that are 120 degrees off from each other.

The only way to get an answer to your question is to look at the spec for your motor.

Answer 2

I do not believe that there is a power factor for single phase motors. The power factor is a measurement of phase angles in relation to each other. Capacitors are used to bring the phases more closely together or above 80%. Power factors are important for high end users of three phase motors. The closer to 100% in phase the less the losses. In other words if your actual use is 100 KWH the if the power factor is 80% you will be charged for 125 KWH. Power factors are measurements of the system supplying the power.