What Is Reactive Power and Its Use?

Reactive power is relatively abstract, it is used to exchange electric and magnetic fields in the circuit, and is used to establish and maintain the electrical power of the magnetic field in electrical equipment. It does not work externally, but instead transforms it into other forms of energy. For electrical equipment with electromagnetic coils, reactive power must be consumed to establish a magnetic field. Because it does not work outside, it is called "reactive." The sign of reactive power is represented by Q, and the unit is either Var or kVar.

 

Reactive power is by no means useless power, and it is very useful. The motor needs to establish and maintain a rotating magnetic field to rotate the rotor, thereby driving the mechanical motion. The rotor magnetic field of the motor is established by taking reactive power from the power source. The transformer also needs reactive power to generate a magnetic field in the primary coil of the transformer and induce a voltage in the secondary coil. Therefore, without reactive power, the motor will not rotate, the transformer will not be transformed, and the AC contactor will not pull.

 

Under normal circumstances, the powered device not only needs to obtain active power from the power supply, but also needs to obtain reactive power from the power supply. If the reactive power in the power grid is in short supply, the power equipment does not have enough reactive power to establish a normal electromagnetic field. Then, the power equipment cannot be operated under the rated condition, and the terminal voltage of the power equipment is lowered. Thereby affecting the normal operation of the electrical equipment. Reactive power has certain adverse effects on supply and use of electricity, mainly in:

 

1. Reduce the output of the generator's active power.

 

2. Reduce the power supply capacity of transmission and transformation equipment.

 

3. This causes an increase in line voltage loss and an increase in power loss.

 

4. This results in low power factor operation and voltage drop, resulting in insufficient electrical equipment capacity.

 

The reactive power supplied from the generator and the high-voltage transmission line can not meet the needs of the load, so some reactive power compensation devices should be set in the power grid to supplement the reactive power to ensure the user's need for reactive power. Electrical equipment can operate at rated voltage. This is the reason why the grid needs to install reactive power compensation devices.