Answer :
In repulsion motor, maximum torque is developed when brush axis is at 45° electrical to the field axis.
asked
Mar 20, 2018
by
anonymous
Answer :
The repulsion-start induction-run motor is used because of high starting torque.
asked
Mar 20, 2018
by
anonymous
Description : Torque developed by a three-phase, 400V, induction motor is 100 N -m. If the applied voltage is reduced to 200-V, the d'veloped torque will be
Answer :
Torque developed by a three-phase, 400V, induction motor is 100 N -m. If the applied voltage is reduced to 200-V, the d'veloped torque will be 25 N -m
asked
Apr 29, 2018
by
anonymous
Answer :
For the same H.P. rating and full load speed, following motor has poor starting torque differentially compounded.
asked
Mar 20, 2018
by
anonymous
Description : In a double squirrel cage induction motor, good starting torque is produced as (A) Large current flows through the outer high resistance winding. (B) Large current flows through the inner high resistance winding. (C) Small current flows through the outer high resistance winding. (D) Large current flows through the inner low resistance winding.
Answer :
In a double squirrel cage induction motor, good starting torque is produced as Large current flows through the outer high resistance winding.
asked
May 8, 2018
by
anonymous
Description : The torque developed by any 3-phase induction motor at 0.8 p.u. slip is (A) Full-load torque (B) unstable torque (C) starting torque (D) break down
Answer :
The torque developed by any 3-phase induction motor at 0.8 p.u. slip is unstable torque
asked
Apr 28, 2018
by
anonymous
Answer :
Capacitor start motor has high torque in starting
asked
Sep 13, 2017
by
anonymous
Description : The speed of a three-phase induction motor is controlled by variable voltage variable frequency control (i.e. keeping V/f constant). As the frequency is reduced, the slip at maximum torque (1) Decreases (2) Increases (3) Remains constant (4) None of the above
Answer :
The speed of a three-phase induction motor is controlled by variable voltage variable frequency control (i.e. keeping V/f constant). As the frequency is reduced, the slip at maximum torque Increases
asked
May 1, 2018
by
anonymous
Description : speed control methods of three phase induction motor?
Answer :
Speed control of three phase induction motor
Answer :
In repulsion motor, zero torque is developed when brush axis coincides with the field axis and brush axis is 90° electrical to field axis.
asked
Mar 20, 2018
by
anonymous
Description : The synchronous speed of an 8 pole induction motor supplied power from a 50 Hz source will be ?
Answer :
Ns equals f/pair pole 50/4 - 12.5
asked
Dec 31, 2017
by
anonymous
Answer :
The purpose of stator winding in the compensated repulsion motor is to improve power factor and provide better speed regulation.
asked
Mar 20, 2018
by
anonymous
Answer :
A repulsion motor is equipped with commutator.
asked
Mar 20, 2018
by
anonymous
Answer :
The armature torque of the D.C. shunt motor is proportional to armature current.
asked
Mar 20, 2018
by
anonymous
Description : In an induction motor if the flux density is reduced to one-half, of its normal value then the torque will (1) reduce to one-half (2) reduce to one-fourth (3) remain unchanged (4) increase four times
Answer :
In an induction motor if the flux density is reduced.to one-half, of its normal value then the torque will reduce to one-fourth
asked
May 1, 2018
by
anonymous
Answer :
In repulsion motor direction of rotation of motor is the same as that of brush shift.
asked
Mar 20, 2018
by
anonymous
Description : A 3-phase, 4-pole, 50Hz induction motor runs at a speed of 1440 rpm. The rotating field produced by the rotor rotates at a speed of ________ rpm with respect to stator field. (A) 1500 (B) 0 (C) 1440 (D) 60
Answer :
0
asked
Apr 28, 2018
by
anonymous
Description : In a 3-phase slip-ring induction motor, the slip at some speed is 0.05. The speed is reduced by inserting an external resistance in the rotor circuit and the slip is 0.15. If the rotor winding resistance per phase is 0.2 Ω, the external resistance is (A) 0.2 Ω (B) 0.3 Ω (C) 0.4 Ω (D) 0.5 Ω
Answer :
In a 3-phase slip-ring induction motor, the slip at some speed is 0.05. The speed is reduced by inserting an external resistance in the rotor circuit and the slip is 0.15. If the rotor winding resistance per phase is 0.2 Ω, the external resistance is 0.3 Ω
asked
Apr 28, 2018
by
anonymous
Answer :
For constant torque drive armature voltage control speed control method is preferred.
asked
Mar 20, 2018
by
anonymous
Answer :
In case of a reluctance motor, when the load is increased so that it cannot maintain synchronous speed the motor will run as induction motor.
asked
Mar 20, 2018
by
anonymous
Answer :
The speed/load characteristics of a universal motor is same as that of D.C. series motor.
asked
Mar 20, 2018
by
anonymous
Description : The speed of a D.C. motor can be controlled by varying 1. Its flux per pole 2. Resistance of armature circuit 3. Applied voltage 4. All of the above
Answer :
The speed of a D.C. motor can be controlled by varying 1. Its flux per pole 2. Resistance of armature circuit 3. Applied voltage 4. All of the above
asked
Mar 20, 2018
by
anonymous
Answer :
The speed of a D.C. shunt motor can be increased by increasing the resistance in field circuit.
asked
Mar 20, 2018
by
anonymous
Answer :
The speed of a D.C. series motor is inversely proportional to the armature current.
asked
Mar 20, 2018
by
anonymous
Answer :
In a D.C. shunt motor, speed is independent of armature current.
asked
Mar 20, 2018
by
anonymous
Answer :
The torque produced in induction type relay (shaded pole structure) is inversely proportional to the square of the current.
asked
Mar 20, 2018
by
anonymous
Answer :
As the load is increased the speed of D.C. shunt motor will reduce slightly.
asked
Mar 20, 2018
by
anonymous
Description : In a split-phase induction motor, the resistance/reactance ratios of windings are such that (A) current in the auxiliary winding leads the current in the main winding (B) current in the auxiliary winding lags the current in the main winding (C) both windings develop the same starting torque (D) both windings develop high starting current
Answer :
In a split-phase induction motor, the resistance/reactance ratios of windings are such that current in the auxiliary winding leads the current in the main winding
asked
Apr 28, 2018
by
anonymous
Description : The torque speed characteristic of a repulsion motor resembles which of the following d.c. motor characteristics A) Separately excited B) Shunt C) Series D) Compound
Answer :
The torque speed characteristic of a repulsion motor resembles which of the following d.c. motor characteristics Series
asked
May 17, 2018
by
anonymous
Answer :
If the centrifugal switch does not open at 70 to 80 percent of synchronous speed of motor, it would result in damage to the starting winding.
asked
Mar 20, 2018
by
anonymous
Answer :
Torque developed by a D.C. motor depends upon magnetic field, active length of the conductor, current flow through the conductors, number of conductors, radius of armature.
asked
Mar 20, 2018
by
anonymous
Description : A change of 4% in the supply voltage to an induction motor will produce a change of approximately
Answer :
A change of 4% in the supply voltage to an induction motor will produce a change of approximately 8% in the rotor torque
asked
May 8, 2018
by
anonymous
Description : In a single-phase induction motor when the rotor is stationary and voltage is applied to the stator, then (A) the flux is constant (B) the flux first decreases and then increases in the same direction (C) the flux increases and decreases in the opposite direction with the same magnitude (D) current flows through the rotor
Answer :
In a single-phase induction motor when the rotor is stationary and voltage is applied to the stator, then the flux first decreases and then increases in the same direction
asked
Apr 28, 2018
by
anonymous
Answer :
Reason is kinetic energy
asked
Mar 20, 2018
by
anonymous
Description : A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s. The armature resistance is 0.5 W and the field winding resistance is 80 W. The net Voltage across armature resistance at the time of plugging will be
Answer :
A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s. The armature resistance is 0.5 W and the field winding resistance is 80 W. The net Voltage across armature resistance at the time of plugging will be 474 V
asked
May 8, 2018
by
anonymous
Description : The speed of a 2-pole, 3-phase stepper motor operated by 1200 pulses/min (A) 100 rpm (B) 200 rpm (C) 400 rpm (D) 800 rpm
Answer :
The speed of a 2-pole, 3-phase stepper motor operated by 1200 pulses/min 200 rpm
asked
Apr 28, 2018
by
anonymous
Answer :
The speed of a universal motor is usually reduced by using gearing.
asked
Mar 20, 2018
by
anonymous
Answer :
Speed control of a universal motor is achieved by varying field flux with tapped field windings, connecting rheostat in series, applying variable voltage by means of silicon controlled rectifier, applying variable voltage by means of variable auto-transformer.
asked
Mar 20, 2018
by
anonymous
Answer :
The rotor slots, in an induction motor, are usually not quite parallel to the shaft because it helps in reducing the tendency of the rotor teeth to remain under the stator teeth.
asked
Mar 20, 2018
by
anonymous
Answer :
In variable speed motor a weaker commutating field is needed at low speed than at high speed.
asked
Mar 20, 2018
by
anonymous
Answer :
Series motor has the poorest speed control.
asked
Mar 20, 2018
by
anonymous
Answer :
Centrifugal switch disconnects the auxiliary winding of the motor at about 70 to 80 percent of synchronous speed.
asked
Mar 20, 2018
by
anonymous
Answer :
The speed control of universal motor used for sewing machines is by varying the resistance.
asked
Mar 20, 2018
by
anonymous
Description : Why the speed of synchronous motor is constant?
asked
Mar 15, 2018
by
anonymous
Description : What are the speed control methods of dc motor?
Answer :
Field control of DC motor Armature control of DC motor
asked
Dec 16, 2017
by
anonymous
Description : A 400 V, 50 Hz three-phase induction motor rotates at 1440 rpm on full -load. The motor is wound for
Answer :
A 400 V, 50 Hz three-phase induction motor rotates at 1440 rpm on full -load. The motor is wound for 4 poles
asked
Apr 29, 2018
by
anonymous
Description : An 8-pole, 50Hz, three-phase induction motor is running at 705rpm and has a rotor copper loss of 5kW. Its rotor input is (A) 5.06 kW (B) 0.3 kW (C) 100 kW (D) 83.33 kW
Answer :
An 8-pole, 50Hz, three-phase induction motor is running at 705rpm and has a rotor copper loss of 5kW. Its rotor input is 83.33 kW
asked
Apr 28, 2018
by
anonymous
Answer :
If starting winding of a single-phase induction motor is left in the circuit, it will draw excessive current and overheat.
asked
Mar 20, 2018
by
anonymous
Answer :
If a single phase induction motor runs slower than normal, the most likely defect is worn bearings.
asked
Mar 20, 2018
by
anonymous
Description : How is a three phase cage induction motor self starting?
Answer :
Any type of induction motor is self starting. Because the reason for torqe production require two flux displaced by some angle theta.If theta is constant with time then torqe will be constant;if ... torqe also pulsating. In induction motor this angle theta is not pulsating.so it is self starting
asked
Mar 17, 2018
by
anonymous