Difference Between Active and Reactive Power – Watts vs VA

Difference Between Active and Reactive Power – Watts vs VA

Difference Between Active and Reactive Power – Watts vs VA

Main Difference Between Active and Reactive Power

The main difference between active and reactive power is that Active Power is actual or real power which is used in the circuit while Reactive power bounce back and forth between load and source which is theoretically useless.

The following power triangle shows the relation between Active, Reactive and Apparent Power. These all powers only induced in AC circuits when current is leading or lagging behind the voltage i.e. there is a phase difference (phase angle (Φ) between voltage and current.

What is Active Power?

The Power which is really utilized and consumed for useful works in AC or DC circuit is known as Active Power. It is also called True Power, Real Power, Useful Power or Watt-full Power. It is denoted by “P” and measured in Watts, kW or MW. The average value of active power can be calculated by the following formulas.

• Definition-

The True or Real or Actual Power dissipated in the circuit is known as Active Power which is actually utilized or consumed.

• Role in DC Circuits-

Active Power is equal to the Reactive Power i.e. there is no VAr in DC Circuits. Only Active Power exists

Formulas for Active Power

• P = V x I x Cosθ  (Single phase AC Circuits)
• P = √3 x VLx IL x Cosθ (Three Phase AC Circuits)
• P = 3 x VPh x IPhx Cosθ
• P = √ (S2 – Q2)or
• P =√ (VA2 – VAR2) or
• P = V x I (DC circuits)

What is Reactive Power

The power which moves and back (bounces back and forth) between source and load in the circuit is known as Reactive Power. It is also called, Useless Power or Watt-less Power. Reactive Power is denoted by “Q” and measured in VAR (Volt Ampere Reactive), kVAR or MVARs.

Reactive Power is useful too i.e. it helps to produce magnetic and electric field and stores in the circuits and discharge by transformers, solenoid, and induction motors etc.

• Definition-

A Power which continuously bounces back and forth between source and load is known as Reactive Power. (Also known as useless or watt-less Power)

• Role in DC Circuits-

There is no Reactive Power in DC circuits due to the zero phase angle (Φ) between current and voltage

Formulas for Reactive Power

• Reactive Power = √(Apparent Power2 –True power2)
• VAR = √ (VA2 – P2)
• kVAR = √ (kVA2 – kW2)
• Q = V x I x Sinθ