Question

A 0.3 kW split-phase motor draws its starting winding current of 3 A lagging the supply voltage by ${15}^{\circ }$ elec and its running winding current is 5 A lagging the supply voltage by ${40}^{\circ }$ elec. The component of current of running winding that lags the supply voltage by ${90}^{\circ }$ will be _______A.

• A. 3.21

Answer 1

The correct option is A 3.21
$\text{Starting winding current}{I}_s=3\angle -15°A=(2.9-j0.78)A$

$\text{Running winding current}{I}_m=5\angle -40°A=(3.83-j3.21)A$

The components of running winding current that lags behind the supply voltage by ${90}^{\circ }$
$\text{= Reactive component of running winding current}$

$=3.21A$