Page 439 - Basic Electrical Engineering

If per phase power is P and total power is P ,
h
T

then P = 3 P (4.8)
h
T

4.6 ACTIVE AND REACTIVE POWER

The in-phase component of I along V has been shown in Fig. 4.10 as I Ph
Ph
cos ϕ and the perpendicular component as I sin ϕ. If we multiply all the
Ph
sides of the triangle ABC by V , the triangle becomes a power triangle
Ph
where AB = V I cos ϕ is called the active power, BC = V I sin ϕ is
Ph Ph
Ph Ph
called the reactive power, and V I is called the apparent power.
Ph Ph

Figure 4.10 Relationship between active power, reactive power, and apparent power

Apparent power = kVA (4.9)

Apparent power × cos ϕ = Active power = kW (4.10)

Apparent power × sin ϕ = Reactive power = kVAR (4.11)

3
Multiplying all the sides of the power triangle by 10 , i.e., expressing the
power in terms of ‘kilo’, the power triangle is redrawn as has been shown in

Fig. 4.8 (c) kVA is kilo Volt Ampere.

kVA cos ϕ = kW (kilo Watt) (4.12)