Methods of Improving Power Factor

List the methods of improving power factor?

• Static capacitors
• Synchronous condenser
• Phase advancers

Static capacitors:

The power factor can be improved by connecting capacitors in parallel with the equipment operating at lagging power factor. The capacitor (Static capacitor) draws a leading current and completely neutralizes the lagging reactive component of load current. This raises the power factor of the load. For 3 phase loads, capacitor connected in delta or star.

Advantages

• Low losses because of no rotating part
• Low maintenance cost,
• in weight, Easy to install
• No foundation required
• Work under all ordinary atmospheric conditions.

Disadvantages:

• Shorter life
• Capacitor can get easily damaged due to over voltage
• Repairing cost is costly and uneconomic
• Due to constant switching surges and harmonics may be produced.

Synchronous condenser

An overexcited synchronous motor running on no load is known as synchronous condenser to improve power factor of a power system. When a synchronous motor runs with over-excitation, it draws leading current from the source, therefore behaves as a capacitor. The main advantage of using synchronous motor is that the improvement of power factor is smooth. Three-phase system, we connect one three-phase synchronous motor is parallel with the supply and run it at no load. It takes leading current which partially neutralizes the lagging reactive component of the load, thus the power factor is improved. The magnitude of current drawn by the motor changed by changing Excitation of the motor.

Advantages:

• Longer life span
• Step less control of power factor
• Flexible & Reliable
• Faults can be removed easily.

Disadvantages

• Higher losses due to rotating part
• Maintenance cost is high, Produce noise
• Synchronous motor has not a self-starting machine
• so we need additional equipment provide for this purpose.

Phase advancers:

Phase advances are used to improve the power factor of induction motors. Phase advancer is a simple AC exciter which is connected on the main shaft of the motor and operates with the motor’s rotor circuit for power factor improvement. Phase advancers are used to improve the power factor of induction motors. The low power factor of an induction motor is due to the fact that its stat or winding draws exciting current which lags be-hind the supply voltage by 90 degrees. If the exciting ampere turns can be provided from some other a.c. source, then the stator winding will be relieved of exciting current and the power factor of the motor can be improved. . It provides exciting ampere turns to the rotor circuit at slip frequency. By providing more ampere turns than required, the induction motor can be made to operate on leading power factor like an over-excited synchronous motor.