Define power factor. Deduce expression for it and explain wattless current
Answers
the ratio of the actual electrical power dissipated by an AC circuit to the product of the r.m.s. values of current and voltage. The difference between the two is caused by reactance in the circuit and represents power that does no useful work.
Power factor is a measure of how efficiently an AC circuit is using the power supplied to it. A low power factor can result in increased energy costs and reduced system efficiency due to the presence of wattless current.
What is power ?
Power factor is defined as the ratio of the real power (in watts) to the apparent power (in volt-amperes) in an AC circuit. It is a measure of how efficiently the circuit is using the total power supplied to it. A circuit with a high power factor is using the supplied power efficiently, while a circuit with a low power factor is using the power inefficiently.
Mathematically, power factor (PF) can be expressed as:
PF = Real Power (W) / Apparent Power (VA)
The real power is the power that is actually used to perform useful work in the circuit, such as lighting a bulb or running a motor. It is measured in watts (W). The apparent power is the total power supplied to the circuit, and is a combination of the real power and the reactive power. It is measured in volt-amperes (VA).
The reactive power is the power that is stored and returned to the circuit in the form of magnetic or electric fields. It does not perform any useful work, but it is necessary to maintain the voltage and current waveforms in an AC circuit. The reactive power is measured in vars (volt-amperes reactive).
A circuit with a low power factor will have a significant amount of reactive power, which results in a lagging current waveform. This lagging current, which is also known as the wattless current, does not perform any useful work and can cause a number of issues, such as increased energy costs and reduced system efficiency.
To reduce the amount of wattless current and improve power factor, a capacitor can be added to the circuit. The capacitor stores energy in the form of an electric field, and returns this energy to the circuit when needed. By adding a capacitor, the reactive power can be reduced, which improves the power factor and increases the efficiency of the circuit.
Therefore, power factor is a measure of how efficiently an AC circuit is using the power supplied to it. A low power factor can result in increased energy costs and reduced system efficiency due to the presence of wattless current. Adding a capacitor to the circuit can reduce the amount of wattless current and improve power factor.
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