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## Related questions

An induction motor having full load torque of 60 Nm when delta connected develops a starting torque of 120 Nm. For the same supply voltage if the motor is changed to star connection, the starting torque developed will be  A) 40 Nm B) 60 Nm C) 90 Nm D) 120 Nm

A d.c. shunt motor runs at no load speed of 1140 r.p.m. At full load armature reaction weakens the main flux by 5%. Whereas the armature circuit voltage drops by 10%. The full load speed of the motor is (a) 1200 r.p.m. (b) 1080 r.p.m. (c) 1040 r.p.m. (d) 1000 r.p.m.

A DC Motor develops a torque of 150 N-m. A 10 percent reduction in the field flux causes a 50 percent increase in armature current. The new value of torque is: A) 102.5 N-m B) 202.5 N-m C) 172.5 N-m D) 232.5 N-m

A 220 V shunt motor develops a torque of 54 N-m at armature current of 10 A. The torque produced when the armature current is 20 A, is?

A d.c. motor develops a torque of 200 N-m at 25 rps. At 20 rps it will develop a torque of .......... N-m.

The d.c. series motor should never be switched on at no load because?

Full load current of an Induction motor is 20 Ampere. The no-load current may be expected to be: A) 25 Ampere to 28 Ampere B) 15 Ampere to 18 Ampere C) 11 Ampere to 14 Ampere D) 6 Ampere to 10 Ampere

The no load speed of a d.c. shunt motor is 1140 rpm. At full load, the armature reaction weakens the main flux by 5% whereas the armature circuit voltage drops by 10%. The motor full load speed in rpm will be: (A) 1080 (B) 1203 (C) 1000 (D) 1200

The no~load current of a single phase induction motor is around _____% of full load current.  (1) 10 (2) 20 (3) 40 (4) 80

The dc motor, which can provide zero speed regulation at full load without any controller is  (A) series (B) shunt (C) cumulative compound (D) differential compound

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) 1.66 Nm (B) 95.50 Nm (C) 99.47 Nm (D) 624.73 Nm

In a 2 kW, 200 V, 1000 rpm. DC series motor the torque at full load was found to be 0.3 N -m. The torque at half full load in N -m is :

A three phase induction motor is driving full -load torque which is independent of speed. If the line voltage drops to 90% of the rated value, % increase in motor copper losses  (a) 23% (b) -18% (c) 123% (d) None of these

As compared to shunt and compound motors, series motor has the highest torque because of its comparatively .......... at the start.

In a battery, the difference between the no-load voltage and the measured voltage output is called ________ A) Internal voltage B) Internal resistance C) External resistance D) All the above

Which of the following plants will take least time in starting from cold conditions to full-load operation? A) Nuclear power plant B) Steam power plant C) Hydro-electric power plant D) Gas turbine plant

A synchronous motor at no load condition is known as synchronous condenser and improves the (a) stability (b) efficiency (c) power factor (d) frequency of the integrated system

If the load current and flux of a d.c. motor are held constant and voltage applied across its armature is increased by 10 per cent, its speed will?

D.C. motor is to drive a load which has certain minimum value for most of the time and some peak value for short duration. We will select the?

The no-load current drawn by transformer is usually what per cent of the full-load current ?

No-load test on a 3-phase induction motor was conducted at different supply voltage and a plot of input power versus voltage was drawn. This curve was extrapolated to intersect the y-axis. The intersection point yields  (A) Core loss (B) Stator copper loss (C) Stray load loss (D) Friction and windage loss

When running under no-load condition and with over excitation, armature current Ia drawn by a synchronous motor

A dc series motor driving and electric train faces a constant power load. It is running at rated speed and rated voltage. If the speed has to be brought down to 0.25 p.u. the supply voltage has to be approximately brought down to  (A) 0.75 p.u (B) 0.5 p.u (C) 0.25 p.u (D) 0.125 p.u

An ideal synchronous motor has no starting torque because the  (a) Rotor is made up of salient poles. (b) Relative velocity between the stator and rotor mmfs is zero. (c) Relative velocity between stator and rotor mmfs is not zero. (d) Rotor winding is highly inductive.

The shaft torque of a d.c. motor is less than its armature torque because of .......... losses.

In a d.c. motor, unidirectional torque is produced with the help of

The power consumed in a circuit element will be least when the phase difference between the current and voltage is?

A 3-phase induction 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 reactance and core loss are ignored  1. The difference between synchronous speed and actual speed remains same 2. The airgap flux remains same 3. The ... . slip remains same Among the above, current statements are  (A) All (B) 1, 2 and 3 (C) 2, 3 and 4 (D) 1 and 4

An 8-pole alternator runs at 750 rpm and supplies power to a 6-pole induction motor which has a full load slip of 3 percent. The full load speed of the induction motor will be: A) 1000 rpm B) 920 rpm C) 950 rpm D) 970 rpm

A three-phase synchronous motor connected to ac mains is running at full load and unity power factor. lf its shaft load is reduced by half and field current is held constant then its new power factor will be

A separately excited d.c. motor fed from single phase full converter with firing angle 60° runs at 1000 r.p.m. If motor is connected to single phase semiconverter with the same firing angle of 60°, it would run at (a) 2000 rpm (b) 1850 rpm (c) 1500 rpm (d) 1000 rpm

Suggest the energy conservation techniques in following cases : (i) Motor is running with 70% loaded condition. (ii) Motor is continuously loaded at 50%. (iii) Motor runs with 30% loaded condition but sometimes rises to 50% loading condition. (iv) Motor runs continuously under no-load condition.

A salient pole synchronous motor is running at no load. Its field current is switched off, the motor will (a) come to stop. (b) continue to run at synch. speed. (c) continue to run at a speed slightly less than synch. speed. (d) continue to run at a speed slightly more than the synch. speed.

The armature resistance of a permanent magnet dc motor is 0.8 Ohm. At no load, the motor draws 1.5 A from a supply voltage of 25 V and runs at 1500 rpm. The efficiency of the motor while it is operating on load at 1500 rpm drawing a current of 3.5 A from the same source will be  (A) 48.0% (B) 57.1% (C) 59.2% (D) 88.8%

Under no load condition, if the applied voltage to an induction motor is reduced from the rated voltage to half the rated value,  (A) the speed decreases and the stator current increases (B) both the speed and the stator current decreases (C) the speed and the stator current remain practically constant (D) there is negligible change in the speed but the stator current decreases

The power factor of an induction motor under no load conditions will be close to (A) 0.2 lagging (B) 0.2 leading (C) 0.5 lagging (D) Unity

The no-load speed of a single-phase SCR bridge converter fed separately excited dc motor operating at a firing delay angle, α and flux, Φ (A) directly proportional to α and Φ (B) inversely proportional to α and Φ (C) directly proportional to α and inversely proportional to Φ (D) directly proportional to Φ and inversely proportional to α

The reading of wattmeter in no load test of induction motor gives : (A) Friction and windage loss (B) Copper losses on no load in the stator (C) Core losses (D) Sum of all losses

Why shouldn’t a DC shunt motor start on the heavy load setting?

Why does the speed of a DC shunt motor decrease as the load increases?

With the increase in load on a d.c. shunt motor, speed of the motor (a) increases proportionately (b) remains constant (c) increase slightly (d) reduces slightly