A balanced three-phase supply is given to a $30 \mathrm{~kW}, 4$-pole, $400 \mathrm{~V}, 50 \mathrm{~Hz}$, wound rotor induction motor with Y-connected stator and rotor windings. The motor is driving a constant torque load. With shorted slip rings, the machine runs at 1476 rpm .

When an external non-inductive resistance of $0.27 \Omega$ per phase is connected in series in the rotor circuit, the steady-state speed drops to 1404 rpm .

Neglecting rotational losses, the actual per phase rotor winding resistance is $\_\_\_\_$ $\Omega$. (Round off to two decimal places)

A 3-phase, $400 \mathrm{~V}, 4$ pole, 50 Hz star connected induction motor has the following parameters referred to the stator :

$$ R_r^{\prime}=1 \Omega, X_S=X_r^{\prime}=2 \Omega $$

Stator resistance, magnetizing reactance and core loss of the motor are neglected. The motor is run with constant V/f control from a drive. For maximum starting torque, the voltage and frequency output, respectively, from the drive, is closest to,

A 3-phase star connected slip ring induction motor has the following parameters referred to the stator:

$R_s = 3\, \Omega,\; X_s = 2\, \Omega,\; X_r' = 2\, \Omega,\; R_r' = 2.5\, \Omega$

The per phase stator to rotor effective turns ratio is 3:1. The rotor winding is also star connected. The magnetizing reactance and core loss of the motor can be neglected. To have maximum torque at starting, the value of the extra resistance in ohms (referred to the rotor side) to be connected in series with each phase of the rotor winding is _______ (rounded off to 2 decimal places).

A three phase 415 V, 50 Hz, 6-pole, 960 RPM, 4 HP squirrel cage induction motor drives a constant torque load at rated speed operating from rated supply and delivering rated output. If the supply voltage and frequency are reduced by 20%, the resultant speed of the motor in RPM (neglecting the stator leakage impedance and rotational losses) is ___________ (Round off to the nearest integer).