# Stator Voltage Control of three phase induction motor

Stator Voltage Control of three phase induction motor

Stator Voltage Control of three phase induction motor

By stator voltage control :

•We have, •Torque is directly proportional to stator voltage square.

•The torque is directly proportional to speed so if torque will decrease speed also decrease and if torque will increase speed also increase.

•So we can control speed of three phase induction motor by varying stator voltage.

•This method is suitable for application where load torque decreases with speed.

•This method is sometimes used for small motor fans.

•This method is very easy and cheap but still use rarely.

•Because by decreasing the voltage torque will reduce.

•But to maintain power (P=VI) this will increase current in motor which will heat the motor which is not good it causes losses.

•Also the torque is proportional to square of voltage so large voltage change is required for changing torque.

## Related questions

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 ... increases and decreases in the opposite direction with the same magnitude (D) current flows through the rotor

Last 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

Description : Explain speed control method of 3 phase induction motor by the following methods: (1) Pole changing (2) Rotor resistance control (3) Stator voltage

Last Answer : 1) Pole Changing Method:  Synchronous speed is given by, From the above equation of synchronous speed, it can be seen that synchronous speed (and hence, running speed) can ... in voltage and consequently the speed decreases and vice versa. Ultimately speed depends on the supply voltage.

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

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Description : In a three-phase, squirrel-cage type, induction motor the rotating magnetic field is established by the _____________. A. current induced in the rotor windings B. application of a three-phase voltage ... caused by the induced current in the squirrel-cage bars with the magnetic field of the stator

Description : The speed of a multi-speed, squirrel-cage, induction motor operating in a fixed frequency system can be changed by _____________. A. reconnecting stator windings for different numbers of poles B. ... sequence of the applied voltage D. reconnecting the stator so that no poles have the same polarity

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

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Description : speed control methods of three phase induction motor?

Last Answer : Speed control of three phase induction motor

Description : The torque and current curves for a three-phase induction motor with a cage rotor, are shown in the illustration. Which of the following statements is true concerning the depicted curves? EL-0056 A. As slip ... D. If the motor is loaded to the point where 40% slip has resulted, it will stall.

Description : A three-phase, squirrel cage, induction motor will run hot due to a/an ______________. A. improper brush position B. reversed commutating pole C. shorted stator D. high power factor

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Description : The rotation of a three-phase induction motor can be reversed by _____________. A. interchanging any two of the three line leads to the stator B. disconnecting one of the three line leads to the ... the shunt field coil leads D. permanently disconnecting any two of the three line leads to the stator

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Description : The stator mmf and rotor mmf of a 3-phase induction motor (A) are equal (B) rotate with slip speed (C) are opposite but rotate with synchronous speed (D) rotate with the same rotor speed

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Description : 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 1.5 kW and 900 W respectively. The friction and windage losses are 1050 W and the ... the motor will be (A) 23.06 kW (B) 24.11 kW (C) 25.01 kW (D) 26.21 kW

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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

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Description : 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 when the motor ... Hz supply is  (A) 58.5 A (B) 45.0 A (C) 42.7 A (D) 55.6 A

Last Answer : 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 when the motor is connected to a 236 , V 57 Hz supply is 45.0 A

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 ... (C) both windings develop the same starting torque (D) both windings develop high starting current

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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

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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

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Last Answer : Reason is kinetic energy

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Last Answer : If a single phase induction motor runs slower than normal, the most likely defect is worn bearings.

Description : How does a single phase induction motor work?

Last Answer : As we know that single phase induction is not self started because for self started we require atleast two revolving field but single phase induction motor has only one. So we provide extra ... 1phase IM classified as split phase IM, capacitor start capacitor run, capacitor start induction run.

Description : explain the working of single phase induction motor.

Last Answer : Stator has two winding namely main winding and auxiliary winding.when single phase ac supply is given to the motor,its produces alternating field.this field cut by a cage rotor.so some emf ... due to this emf,rotor flux produced.the interaction between two fluxes produce torque.so rotor rotates.

Last Answer : Capacitor start motor has high torque in starting

Description : Single Phase Induction Motor

Last Answer : Single Phase Induction Motor Single phase induction motor is mostly used in home, office, shop and many single phase appliances like pumps,  ... torque and silent operation. It is uses where silent operation is required.

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Last Answer : A change of 4% in the supply voltage to an induction motor will produce a change of approximately 8% in the rotor torque

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Description : A 4-pole, 3-phase, double-layer winding is housed in a 36-slot stator for an ac machine with 60o phase spread. Coil span is 7 short pitches. Number of slots in which top and bottom layers belong to different phases is  (A) 24 (B) 18 (C) 12 (D) 0

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Description : The variable resistance placed in the rotor circuit of a wound-rotor induction motor provides for __________. A. speed control B. frequency control C. voltage control D. use as a split-phase motor

Description : In a 3-phase voltage source inverter used for speed control of induction motor, anti-parallel diodes are used across each switching device. The main purpose of diodes is to:

Last Answer : In a 3-phase voltage source inverter used for speed control of induction motor, anti-parallel diodes are used across each switching device. The main purpose of diodes is to: Allow the motor to return energy during regeneration

Description : The air gap in an induction motor should be periodically checked with a feeler gage to prevent possible ___________. A. rotor contact with the stator B. axial misalignment of the rotor C. damage to the motor bearings D. electrical damage to the bearings

Description : The speed of a squirrel-cage induction motor is determined by the ____________. A. diameter of the stator B. number of stator poles C. rotor winding resistance D. rotor conducting bars resistance