$9\mathrm{.}3\mathrm{.}2$ Speed Control Methods

Example: A $3-$phase, $30hp,480V,6-$pole, $60Hz,Y-$connected$-$slip$-$ring induction motor has the following parameters:

$R_1=0\mathrm{.}5,R_2^{\text{'}}=0\mathrm{.}5,x_{cq}=5$

The load torque is constant and equal to $120$ Nm $.$

Calculate the motor speed at full voltage.

Calculate the motor speed if the voltage is reduced by $20\%.$