Page 449 - Basic Electrical Engineering

Power factor = cos ϕ = cos 37° = 0.8 lagging

Active power = V I cos ϕ
L L
= 1.732 × 400 × 23.1 × 0.8

= 12802 W = 12.802 kW

Reactive power = V I sin ϕ
L L
= 1.732 × 400 × 23.1 × 0.6

= 9602 VAR = 9.602 kVAR

Example 4.9 A delta-connected three-phase motor load is supplied from a

400 V, thee-phase, 50 Hz supply system. The line current drawn is 21 A. The
input power is 11 kW. What will be the line current and power factor when

the motor windings are delta connected?

Solution:

Line voltage, V = 400 V, V = V for delta connection
Ph
L
L
Line current, I = I = 21A
Ph
L

Impedance of each winding,

or,

When the motor windings are star connected