Improve Power Factor with PFC Equipment
Power Factor Correction
Transmission and distribution of electrical energy brings in the question of power factor improvement with the use of pfc equipments. Most of the loads are inductive hence giving a lagging power factor. A lagging power factor causes an increase in current. The increased current causes more power losses of active power. It is essential to have a power factor close to unity.
Power factor of an alternating circuit is the ratio of real power to the apparent power or the cosine of the angle between current and voltage of an alternating current circuit. Power factor is the ratio between resistances to the impedance of an AC circuit. There is a phase difference between current and voltage. The current lags behind the voltage in an inductive circuit while in a capacitive circuit the current leads the voltage.
The value of the power factor is never more than one. It is good practice to attach the word leading or lagging when describing power factor.
Demerits of low power factor
Increase in the kVA rating of an equipment. A small power factor will mean a larger kVA rating of the equipment. This makes the equipment expensive and larger.
Low power factor means greater conductor size of the equipment
It causes larger copper losses. This causes low efficiency
It causes more voltage drop in transmission lines, transformers and alternators. This results in poor voltage regulation.
Low power factor results in a low handling capacity of the system.
Causes of low power factor
Most ac motors are induction type. Induction type motors always have a lagging power factor. The motors work at very small power factors.
Electric discharge lamps, arc lamps and industrial heating furnaces work at very low power factors.
There is varying load on a power system. The load is high in the morning/evening and low during the rest of the day. At low loads, the voltage increases thus increasing the magnetization current. This leads to a low power factor.
Improvement of low power factor is by the use of the following equipment.
Power factor correction is by connecting static capacitors in parallel with the equipment causing low power factor. The capacitors draw a leading current. They also neutralize the reactive component of the load current. Capacitor connection is by either in star or delta method.
The static capacitors require little maintenance, and they have low losses.
An over excited synchronous motor takes a leading current. The motor at no load is a synchronous condenser. When connected in parallel with the supply, motors neutralize the lagging component of the load thus improving the power factor.
Step less control of the power factor when using synchronous condensers is possible.
Phase advancers are ac exciters. The exciter is mounted is connected on the rotor circuit and on the same shaft as the motor. It gives over excited current per turn to the rotor circuit. This improves the power factor.
For more information and a solution to determining and improving the power factor of your equipment, you should visit www.electricsaver1200.com. We offer expert technical advice to all your problems.