The _______ of a motor depends on the loading of the motor.

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ALP CBT 2 Electrician Previous Paper: Held on 22 Jan 2019 Shift 2

Answer 1

Power factor = cosϕ = (P)/(S)

When the load on a motor increases, the active power increases while the reactive power remains constant. Thus, the angle of ϕ decreases and the power factor (cos ϕ) improves slightly.
The PF of a motor is lower when the motor is under-loaded and is significantly reduced when the motor load is less than 70%.
Closely matching the motor to the load is the best way to keep the power factor close to the motor design rating, which is typically 80% to 85% PF.