Induction Motors

Which one of the following options is correct regarding the typical double-squirrel-cage structure used in induction motors?

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 react...

A three phase, 50 Hz, 6 pole induction motor runs at 960 rpm. The stator copper loss, core loss, and the rotational loss of the motor can be neglected. The percentage efficiency of the motor is

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 eff...

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 ar...

The following columns present various modes of induction machine operation and the ranges of slip A B Mode of operation Range of Slip a. Running in generator mode p) From 0.0 to 1.0 b. Running in motor mode q) From 1.0 t...

A 10-pole, 50 Hz, 240 V, single phase induction motor runs at 540 RPM while driving rated load. The frequency of induced rotor currents due to backward field is

A 3-phase, 415 V, 50 Hz induction motor draws 5 times the rated current at rated voltage at starting. It is required to bring down the starting current from the supply to 2 times of the rated current using a 3-phase auto...

The type of single-phase induction motor, expected to have the maximum power factor during steady state running condition, is

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

The power input to a $500 \mathrm{~V}, 50 \mathrm{~Hz}, 6$ pole, 3 phase induction motor running at 975 rpm is 40 kW . The stator losses are 1 kW . If the total friction and windage losses are 2.025 kW , then the efficie...

An 8 pole, $50 \mathrm{~Hz}, 3$ phase, slip-ring induction motor has an effective rotor resistance of $0.08 \Omega$ per phase. Its speed at maximum torque is 650 rpm . The additional resistance per phase that must be ins...

A 375W, 230 V, 50 Hz capacitor start single-phase induction motor has the following constants for the main and auxiliary windings (at starting): $$Z_m=\left(12.50\;+\;j15.75\right)\;\Omega$$ (main winding), $$Z_a=\left(2...

A 3-phase, 4-pole, 400 V, 50 Hz squirrel-cage induction motor is operating at a slip of 0.02. The speed of the rotor flux in mechanical rad/sec, sensed by a stationary observer, is closest to

A star-connected, 12.5 kW, 208 V (line), 3-phase, 60 Hz squirrel cage induction motor has following equivalent circuit parameters per phase referred to the stator. R 1 = 0.3 Ω, R 2 = 0.3 Ω, X 1 = 0.41 Ω, X 2 = 0.41 Ω. Ne...

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

In a constant V/f induction motor drive, the slip at the maximum torque

The direction of rotation of a single-phase capacitor run induction motor is reversed by

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 5 th harmonic component. If the operating slip of the motor with respect to fundamental component volt...

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 th...

A three-phase, 4-pole, self excited induction generator is feeding power to a load at a frequency $$f_1$$. If the load is partially removed, the frequency becomes $$f_2$$. If the speed of the generator is maintained at 1...

An 8-pole, 3-phase, 50 Hz induction motor is operating at a speed of 700 rpm. The frequency of the rotor current of the motor in Hz is ________.

A 3 phase, 50 Hz, 6 pole induction motor has a rotor resistance of 0.1 Ω and reactance of 0.92 Ω. Neglect the voltage drop in stator and assume that the rotor resistance is constant. Given that the full load slip is 3%,...

A single phase induction motor is provided with capacitor and centrifugal switch in series with auxiliary winding. The switch is expected to operate at a speed of 0.7 Ns, but due to malfunctioning the switch fails to ope...

In a constant V/f control of induction motor, the ratio V/f is maintained constant from 0 to base frequency, where V is the voltage applied to the motor at fundamental frequency f. Which of the following statements relat...

A 4-pole induction motor, supplied by a slightly unbalanced three-phase 50Hz source, is rotating at 1440 rpm. The electrical frequency in Hz of the induced negative sequence current in the rotor is

Leakage flux in an induction motor is

The locked rotor current in a 3-phase, star connected 15 kW, 4-pole, 230 V, 50 Hz induction motor at rated conditions is 50 A. Neglecting losses and magnetizing current, the approximate locked rotor line current drawn wh...

The slip of an induction motor normally does not depend on

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

A balanced three-phase voltage is applied to a star-connected induction motor, the phase to neutral voltage being V. The stator resistance, rotor resistance referred to the stator, stator leakage reactance, rotor leakage...

A $$400$$ $$V,$$ $$50$$ $$Hz$$, $$4$$ pole, $$1400$$ $$rpm$$, star connected squirrel cage induction motor has the following parameters referred to the stator: $$R = 1.0\,\Omega ,{X_s} = X{'_r} = 1.5\,\Omega $$ Neglect s...

A $$400$$ $$V,$$ $$50$$ $$Hz,$$ $$30$$ $$hp,$$ three-phase induction motor is drawing $$50$$ A current at $$0.8$$ power factor lagging. The stator and rotor copper losses are $$1.5kW$$ and $$900$$ $$W$$ respectively. The...

A $$230V,$$ $$50Hz,$$ $$4$$ pole, single phase induction motor is rotating in the clockwise (forward) direction at a speed of $$1425$$ $$rpm.$$ If the rotor resistance at standstill is $$7.8\,\,\Omega ,$$ then the effect...

A three phase squirrel cage induction motor has a starting current of seven times the full load current and full load slip of $$5\% $$ If an auto-transformer is used for reduced voltage starting to provide $$1.5$$ per un...

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 rota...

A three phase squirrel cage induction motor has a starting current of seven times the full load current and full load slip of $$5\% $$ If a starting torque of $$0.5$$ per unit is required then the per unit starting curre...

A three phase squirrel cage induction motor has a starting current of seven times the full load current and full load slip of $$5\% $$ If a star-delta starter is used to start this induction motor, the per unit staring t...

A $$3$$ phase, $$10$$ $$kW$$, $$400$$ $$V,$$ $$4$$ pole, $$50$$ $$Hz$$, star connected induction motor draws $$20$$ A on full load. Its no load and blocked rotor test data are given below. No Load Test: $$400V$$ $$6A$$ $...

The speed of a $$4$$-pole induction motor is controlled by varying the supply frequency while maintaining the ratio of supply voltage to supply frequency $$(V/f)$$ constant. At rated frequency of $$50$$ $$Hz$$ and rated...

A $$3$$ phase, $$4$$ pole, $$400$$ $$V,$$ $$50$$ $$Hz,$$ star connected induction motor has following circuit parameters $${r_1} = 1.0\Omega ,\,{r_2} = 0.5\Omega ,$$ $${\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {x_1} = x{'_2...

Under no load condition, if the applied voltage to an induction motor is reduced from the rated voltage to half the rated value,

Assertion [a]: Under V/f control of induction motor, the maximum value of the developed torque remains constant over a wide range of speed in the subsynchronous region. Reason [r]: The magnetic flux is maintained almost...

In a single phase induction motor driving a fan load, the reason for having a high resistance rotor is to achieve

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 startin...

For an induction motor, operating at a slip 's', the ratio of gross power output to air gap power is equal to:

A single-phase, 230 V, 50 Hz, 4 pole, capacitor-start induction motor has the following stand still impedances Main winding Z m =6.0 + j4.0Ω Auxiliary winding Z a = 8.0 + j6.0Ω The value of the starting capacitor require...

The direction of rotation of a 3-phase induction motor is clockwise when it is supplied with 3-phase sinusoidal voltage having phase sequence A-B-C. For counter clockwise rotation of the motor, the phase sequence of the...

The type of single-phase induction motor having the highest power factor at full load is

The synchronous speed for the seventh space harmonic $$mmf$$ wave of a $$3$$-phase, $$8$$ pole, $$50$$ $$Hz$$ induction machine is

A 400 V, 15 kW, 4 pole, 50 Hz, Y-connected induction motor has full load slip of 4%. The output torque of the machine at full load is

A single phase induction motor with only the main winding excited would exhibit the following response at synchronous speed

No-load test on a 3-phase induction motor was conducted at different supply voltages and a plot of input power versus voltage was drawn. This curve was extrapolated to intersect the y-axis. This intersection point yields

A 3-phase Inductor Motor is driving a constant torque load at rated voltage and frequency. If both voltage and frequency are halved, following statements relate to the new condition if stator resistance, leakage reactanc...

A $$4$$-pole, $$3$$-phase, double layer winding is housed in a $$36$$-slot stator for an $$ac$$ machine with $$60$$ degree phase spread. Coil span is $$7$$ slot pitches. Number of slots in which top and bottom layers bel...

If a 400 V, 50 Hz, star connected, 3 phase squirrel cage induction motor is operated from a 400 V, 75 Hz supply, the torque that the motor can now provide while drawing rated current from the supply?

A 3-phase, 4-pole squirrel cage induction motor has 36 stator and 28 rotor slots. The number of phases in the rotor is:

The power input to a 415 V, 50 Hz, 6 pole, 3-phase induction motor running at 975 rpm is 40 kW. The stator losses are 1kW and friction and windage losses total 2 kW. The efficiency of the motor is

A three phase, wound rotor induction motor is to be operated with slip energy recovery in the constant torque mode, when it delivers an output power P 0 at slop 's'. then theoretically, the maximum power that is availabl...

Starting torque can be obtained in the case of a single phase induction motor with identical main and auxiliary windings by connecting

The following starting method for an induction motor is inferior view of the poor starting torque per ampere of the line current drawn:

A 3-phase squirrel cage induction motor has a full load efficiency of 0.8 and a maximum efficiency of 0.9. It is operated at a slip of 0.6 by applying a reduced voltage. The efficiency of the motor at this operating poin...

If an induction machine is run at above synchronous speed, it acts as

An induction motor having full load torque of $$60$$ $$Nm$$ when delta-connected develops a starting torque of $$120$$ $$N$$-$$m.$$ For the same simply voltage, if the motor is changed to star-connection, the starting to...

In case of a split phase motor, the phase shift between currents in the two windings is around

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

In an induction motor, if the air gap is increased

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

Skew is used in induction motors in order to reduce torque due to

A three phase slip ring induction motor is fed from the rotor side with stator winding short circuited. The frequency of the currents flowing in the short circuited stator is