The operating region of the developed torque   and speed () of an induction motor drive is given by the shaded region OQRE in the figure. The load torque  characteristic is also shown. The motor drive moves from the initial operating point O to the final operating point S. Which one of the following trajectories will take the shortest time?

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

The per phase stator to rotor effective turns ratio is . 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).

The following columns present various modes of induction machine operation and the ranges of slip

The correct matching between the elements in column A with those of column B is

The frequencies of the stator and rotor currents flowing in a three-phase 8-pole induction motor are 40 Hz and 1 Hz, respectively. The motor speed, in rpm, is _________ (round off to nearest integer).

A 4 pole induction machine is working as an induction generator. The generator supply frequency is 60 Hz. The rotor current frequency is 5 Hz. The mechanical speed of the rotor in RPM is

A 3 – phase 50 Hz square wave (6-step) VSI feeds a 3 – phase, 4 pole induction motor. The VSI line voltage has a dominant  harmonic component. If the operating slip of the motor with respect to fundamental component voltages is 0.04, the slip of the motor with respect to  harmonic component of voltage is __________________.

A 220 V, 3-phase, 4-pole, 50 Hz inductor motor of wound rotor type is supplied at rated voltage and frequency. The stator resistance, magnetizing reactance, and core loss are negligible. The maximum torque produced by the rotor is 225% of full load torque and it occurs at 15% slip. The actual rotor resistance is 0.03. The value of external resistance (in Ohm) which must be inserted in a rotor phase if the maximum torque is to occur at start is______.

A 3 phase, 50Hz, six pole induction motor has a rotor resistance of  and reactance of . Neglect the voltage drop in stator and assume that the rotor resistance is constant.

Given that the full load slip of 3%, the ratio of maximum torque to full load torque is

The slip of an induction motor normally does not depend on

A three-phase 440V, 6pole, 50Hz, squirrel cage induction motor is running at a slip of 5%. The speed of stator magnetic field with respect to rotor magnetic field and speed of rotor with respect to state magnetic field are

A 3-phase squirrel cage induction motor supplied from a balanced 3-phase source drives a mechanical load. The torque-speed characteristics of the motor (solid curve) and of the load (dotted curve) are shown. Of the two equilibrium points A and B. which of the following options correctly describes the stability of A and B?

A three-phase squirrel cage induction motor has a starting torque of 150% and a maximum torque of 300% with respect to rated torque at rated voltage and rated frequency. Neglect the stator resistance and rotational losses. The value of slip for maximum torque

On the torque/speed curve of induction motor shown in Figure, four points of operation are market as W, X, Y and Z. Which one of them represents the operation at a slip greater than 1?

A three-phase cage induction motor is started by direct-on-line (DOL) switching at the rated voltage. If the starting current drawn is 6 times the full load current, and the full load slip is 4%, the ratio of the starting developed torque to the full load torque is approximately equal to

Unbalanced supply voltage given to a 3-phase, delta-connected induction motor will cause

When the supply voltage to an induction motor is reduced by 10%, the maximum torque will decrease by approximately

Out of the several characteristics shown in figure identify the appropriate ones to match the following for a 3-phase induction motor.

 x-axis                        y-axis

(a) Load         efficiency                (P) curve-I

(b) Speed        current                 (Q) curve-II

(c) Speed         power factor        (R) curve-III

                        (S) curve-IV

                                (T) curve-V

An induction motor runs stably under constant torque load at 1250 rpm off a 50Hz supply. Its number of poles is _______________

Motor characteristics         

(a) Speed torque characteristics of induction machine under motoring operation.

(b) Current torque characteristics of a dc series motor

(c) Power factor variation with voltage of an induction motor under no-load operation

(d) Speed torque characteristics of induction machine under dc injection dynamic braking operation

(e) Speed torque characteristics of dc series motor.

A six pole 50Hz induction motor rotating at 1400 rpm is in generating mode. (True=1/False=0)