Engineering Q&A
Explain speed control method of 3 phase induction motor by the following methods: (1) Pole changing (2) Rotor resistance control (3) Stator voltage
in AC machine by

1 Answer

0 like 0 dislike

1) Pole Changing Method: 


Synchronous speed is given by,image

From the above equation of synchronous speed, it can be seen that synchronous speed (and hence, running speed) can be changed by changing the number of stator poles. This method is generally used for squirrel cage induction motors as squirrel cage rotor adopts itself for any number of stator poles. Change in stator poles is achieved by two or more independent stator windings wound for different number of poles in same slots. 


ii)Rotor Resistance Control Method: This method is only applicable to slip ring motors, as addition of external resistance in the rotor of squirrel cage motors is not possible. The speed of the motor can be decreased by adding external resistance to the rotor. Under normal running condition T ∝ s/R2, where R2 is rotor resistance per phase. Therefore, for same load torque, slip can be increased (i.e. motor speed can be decreased) by increasing the rotor resistance and vice versa.


iii)Stator Voltage Control Method: As in three phase induction motor, the torque produced, T ∝ sE22 where E2 is rotor induced emf and E2 ∝ V. Thus, T ∝ sV2 , which means, if supplied voltage is decreased, the developed torque decreases. Hence, for providing the same load torque, the slip increases with decrease in voltage and consequently the speed decreases and vice versa. Ultimately speed depends on the supply voltage.

by

Related questions

1 answer
Welcome to electronics2electrical.com, where students and teachers can ask and answer any question. Get help and answers to any engineering problem including Electrical, electronics, mechanical, telecommunication, instrumentation, computer, mathematics, physics etc. Get answers to questions. Help is always 100% free!

Most popular tags

power motor dc circuit transformer voltage current system used phase factor resistance ac load synchronous induction energy electric generator electrical series frequency capacitor between plant line speed transmission use meter type advantages difference single mosfet control instrument function magnetic amplifier problem high diode bjt machine unit source motors and diagram winding shunt field define electricity torque value parallel maximum relay arduino supply time digital armature types applications thyristor working transformers wave on flow operation three coil material instruments state ratio signal emf effect formula efficiency theorem method disadvantages starting microprocessor test operating direction controlled different logic transistor single-phase network scr loss temperature connected rc law force inductance compare measure station wire low conductor principle wattmeter full characteristics measuring constant measurement breaker losses device converter bridge linear materials nuclear matrix flux drive resistivity machines angle switch free rectifier of protection core battery solar gain thermal loop generators open circuits negative analog number lines friction reactance short gate pole inverter the conservation diesel iron capacitance engineering basic direct main electronics a steam induced relays resistors hysteresis universal transducer computer feedback using range electronic distribution work secondary igbt algebra pmmc plants factors capacitors dielectric controller regulation systems design air fault components rotor cable starter oscillator eddy alternator application semiconductor ammeter rl average forces damping rlc connection zener electromagnetic biasing minimum insulation pressure balanced permanent moving errors running copper self impedance stability quality start ideal curve over commutation 3-phase arc permeability peak bias error fuzzy commutator conductors superposition density mechanical rotation construction measured electrons charge memory inductive transfer explain fuse methods off back is three-phase tariff locomotive installation welding heating rms surge rating generation potentiometer coupled shaded rate capacity storage adc excitation active two pure harmonics reluctance microcontroller voltmeter inductor internal 8085 cro reaction insulating overhead hydro resonance traction definition breakers earth neutral designed

9,167 questions

7,914 answers

151 comments

3,290 users

9,167 questions
7,914 answers
151 comments
3,290 users