Active power is the real power that does useful work in an electrical circuit. It is the power that is used to light bulbs, run motors, and power other devices. Active power is measured in watts (W).
Reactive power is the power that flows back and forth between the source and load in an electrical circuit. It does not do any useful work, but it is necessary for the operation of certain types of loads, such as inductive and capacitive loads. Reactive power is measured in volt-amperes reactive (VAR).
The relationship between active and reactive power can be represented by the following equation:
Apparent power (VA) = √(Active power^2 + Reactive power^2)
Apparent power is the total power that is drawn by a load. It is measured in volt-amperes (VA).
The power factor of a load is the ratio of active power to apparent power. It is a measure of how efficiently a load is using the power that it is drawing. A power factor of 1 indicates that the load is using all of the power that it is drawing efficiently. A power factor of less than 1 indicates that the load is not using all of the power that it is drawing efficiently.
Here is a table that summarizes the key differences between active and reactive power:
| Characteristic | Active power | Reactive power |
|---|---|---|
| Definition | The real power that does useful work in an electrical circuit. | The power that flows back and forth between the source and load in an electrical circuit. |
| Unit of measurement | Watts (W) | Volt-amperes reactive (VAR) |
| Relationship to apparent power | Active power = Apparent power * Cos(φ), where φ is the phase angle between voltage and current. | Reactive power = Apparent power * Sin(φ) |
| Effect on power factor | Improves power factor. | Reduces power factor. |
| Examples of loads | Light bulbs, motors, heaters. | Transformers, capacitors, inductors. |
Here are some examples of how active and reactive power are used in different types of loads:
- Resistive loads: Resistive loads, such as incandescent light bulbs and heaters, consume only active power.
- Inductive loads: Inductive loads, such as motors and transformers, consume both active and reactive power. The reactive power consumed by an inductive load is necessary to create the magnetic field that the load needs to operate.
- Capacitive loads: Capacitive loads, such as capacitors and power factor correction capacitors, consume only reactive power. Capacitive loads can be used to improve the power factor of a load by canceling out some of the reactive power consumed by inductive loads.
Power factor correction is the process of improving the power factor of a load. There are two main types of power factor correction:
- Passive power factor correction: Passive power factor correction involves adding capacitors or inductors to the circuit to cancel out some of the reactive power consumed by the load.
- Active power factor correction: Active power factor correction uses electronic devices to generate or absorb reactive power, depending on the needs of the load.