RELATION BETWEEN ACTIVE AND REACTIVE POWER

Active and Reactive Power

•         Active power (kW): real power used

•         Reactive power (kVAR): virtual power that determines load/demand

•         Utility pays for total power (kVA)

•         Active power, measured in kilowatt (kW), is the real power (shaft power, true power) used by a load to perform a certain task. However, there are certain loads like motors, which require another form of power called reactive power (kVAR) to establish the magnetic field. Although reactive power is virtual, it actually determines the load (demand) on an electrical system. The utility has to pay for total power (or demand)

•         The vector sum of the active power and reactive power is the total (or apparent) power, measured in kVA (kilo Volts-Amperes). This is the power sent by the power company to customers.

•         Here the different powers are represented of a power triangle where the vector sum of the active power and reactive power make up the total power used. This is the power sent by the power utility companies for the user to perform a given amount of work. Total power, also known as apparent power is measured in kilo Volts-Amperes.

•         You can see from the figure that the active power, and the reactive power required are 90 degrees apart vectorically in a pure inductive circuit. In other words reactive power kVAr lagging the active kW. The apparent power, kVA, is the vector sum of active and reactive power. Mathematically it may be represented with the following formula

kVA = Ö (KW)2 + (KVAR)2