Question

A 400 V, 50 Hz, 35 hp, 3-$\varphi$ induction motor is drawing 50 A current at 0.8 power factor lagging. The rotor and stator copper losses are 950 W and 1.5 kW respectively. The friction and windage losses are 1 kW and core losses are 1.2 kW. The value of air gap power is ________ kW.

• A. 25

Answer 1

The correct option is A 25
$\text{Given,}$ $I_L=50A,V_L=400V$

$cos\varphi =0.8\left(lag\right)$

$\text{Input power}$ $=P_{in}=\sqrt{3}{V}_L{I}_{L}cos\varphi$

$=\sqrt{3}\times 400\times 50\times 0.8=27712.8W$

$P_{cu\left(stator\right)}=1.5kW,P_{cu\left(rotor\right)}=950W$

$P_{fw}=1000W,P_{core}=1200W$

$P_g$ $\text{= air gap power}$

$=P_{in}-P_{cu\left(stator\right)}-P_{core}$

$=27712.8-1500-1200=25012.8W$

$\simeq 25kW$