Power Factor is the ratio between the useful (true) power (kW) to the total (apparent) power (kVA) consumed by an item of a.c electrical equipment or a complete electrical installation. It is a measure of how efficiently electrical power is converted into useful work output. Or the cosine of angle between voltage and current in an a.c circuit is known as power factor.
In electricity supply system and on the consumer’s bill a poor power factor is usually the result of a significant phase difference between the voltage and current at the load terminals, or it can be due to a high harmonic content or a distorted current waveform.
Power factor correction Power factor correction is the term given to a technology that has been used since the turn of the 20th century to restore the power factor to as close to unity as is economically viable. This is normally achieved by the addition of capacitors to the electrical network which compensate for the reactive power demand of the inductive load and thus reduce the burden on the supply. There should be no effect on the operation of the equipment. To reduce losses in the distribution system, and to reduce the electricity bill, power factor correction, usually in the form of capacitors, is added to neutralize as much of the magnetizing current as possible. Capacitors contained in most power factor correction equipment draw current that leads the voltage, thus producing a leading power factor. If capacitors are connected to a circuit that operates at a nominally lagging power factor, the extent that the circuit lags is reduced proportionately. Typically the corrected power factor will be 0.92 to 0.95. Some power distributors offer incentives for operating with a power factor of better than 0.9, for example, and some penalize consumers with a poor power factor. There are many ways that this is metered but the net result is that in order to reduce wasted energy in the distribution system, the consumer is encouraged to apply power factor correction.
Disadvantages of Low Power Factor
(i) Large kVA rating of equipment. (ii) Greater conductor size. (iii) Large copper losses..
(iv) Poor voltage regulation. (v) Reduced handling capacity of system.
Causes of Low Power Factor
Low power factor is undesirable from economic point of view. Normally, the power factor of the whole load on the supply system in lower than 0•8. The following are the causes of low power factor:
(i) Most of the a.c. motors are of induction type (1and 3induction motors) which have low lagging power factor. These motors work at a power factor which is extremely small on light load (0•2 to 0•3) and rises to 0•8 or 0•9 at full load.
(ii) Arc lamps, electric discharge lamps and industrial heating furnaces operate at low lagging power factor.
(iii) The load on the power system is varying ; being high during morning and evening and low at
other times. During low load period, supply voltage is increased which increases the magnetization current. This results in the decreased power factor.
Power Factor Improvement Equipment
This can be achieved by the following equipment :
1. Static capacitors.
2. Synchronous condenser.
3. Phase advancers.
In electricity supply system and on the consumer’s bill a poor power factor is usually the result of a significant phase difference between the voltage and current at the load terminals, or it can be due to a high harmonic content or a distorted current waveform.
Power factor correction Power factor correction is the term given to a technology that has been used since the turn of the 20th century to restore the power factor to as close to unity as is economically viable. This is normally achieved by the addition of capacitors to the electrical network which compensate for the reactive power demand of the inductive load and thus reduce the burden on the supply. There should be no effect on the operation of the equipment. To reduce losses in the distribution system, and to reduce the electricity bill, power factor correction, usually in the form of capacitors, is added to neutralize as much of the magnetizing current as possible. Capacitors contained in most power factor correction equipment draw current that leads the voltage, thus producing a leading power factor. If capacitors are connected to a circuit that operates at a nominally lagging power factor, the extent that the circuit lags is reduced proportionately. Typically the corrected power factor will be 0.92 to 0.95. Some power distributors offer incentives for operating with a power factor of better than 0.9, for example, and some penalize consumers with a poor power factor. There are many ways that this is metered but the net result is that in order to reduce wasted energy in the distribution system, the consumer is encouraged to apply power factor correction.
Disadvantages of Low Power Factor
(i) Large kVA rating of equipment. (ii) Greater conductor size. (iii) Large copper losses..
(iv) Poor voltage regulation. (v) Reduced handling capacity of system.
Causes of Low Power Factor
Low power factor is undesirable from economic point of view. Normally, the power factor of the whole load on the supply system in lower than 0•8. The following are the causes of low power factor:
(i) Most of the a.c. motors are of induction type (1and 3induction motors) which have low lagging power factor. These motors work at a power factor which is extremely small on light load (0•2 to 0•3) and rises to 0•8 or 0•9 at full load.
(ii) Arc lamps, electric discharge lamps and industrial heating furnaces operate at low lagging power factor.
(iii) The load on the power system is varying ; being high during morning and evening and low at
other times. During low load period, supply voltage is increased which increases the magnetization current. This results in the decreased power factor.
Power Factor Improvement Equipment
This can be achieved by the following equipment :
1. Static capacitors.
2. Synchronous condenser.
3. Phase advancers.
Open up
