Why improve power factor?

Answer 1

A poor power factor is usually caused by coils; by inductors within electric motors. A capacitor is the opposite of a coil, and can improve the power factor by moving the current phase angle forward, more towards the voltage.

Power factor degradation from inductive loads occurs because inductors resist a change in current, by "presenting" a higher resistance to a step (or any) change in current. As a result, current lags voltage, and power factor suffers.

Capacitors are opposite to inductors. They resist a change in voltage, by "presenting" a lower resistance to a change in voltage. As a result, current leads voltage.

Suppose that a capacitor is placed in parallel to an inductor. If the value of capacitance is adjusted so it exactly cancels the inductance at 60Hz, then the combination as a whole behaves purely as a resistor.

If capacitive loads were common, then they would cause problems similar to inductors.

However, adding capacitance in a case where there is also inductance serves to raise voltage, particularly since the conductors (power lines, etc.) leading up to the load are also resistive, inductive, and partially capacitive. By raising the voltage, power factor is improved, and the inductive loads (usually motors) cause fewer losses in power lines.

Answer 2

To reduce load currents, which reduces that amount of copper required to supply a particular load. It has no effect on energy consumption, but industrial and commercial consumers may be penalised by their utility companies if they allow the power factor of their installations to become too low.

Answer 3

By capactor bank & syncronous motor.