EE213 - 38 - Synchronous motors - Equivalent Circuit and Working

This lecture describes the equivalent electrical circuit of a synchronous motor. The working of synchronous motor is also explained with the help of phasor diagrams.

[@casdoorcasdooor3117]

Thanks sir for this video series it's really educative and informativie. Pls we want a lecture about the 3 phase machine winding

[@MAFarooqi]

Thanks that you liked it. The course in current semester covers basic theoretical concepts of Electrical Machines. However, I shall try to upload lectures on advanced topic as soon as possible.

[@ranarehman553]

Sir how is Bs still rotating with the same speed when we remove the prime mover ? Because as Br slows down the frequency of volatage in coil decreases and thus the speed of magnetic field i.e. Bs produced by them decreases.

[@MAFarooqi]

Bs is due to current in the stator and it's speed of rotation is dependent upon the frequency of the current flowing in the stator windings. In case of synchronous motor, the current in stator windings is due to three phase supply connected to the stator. Therefore, speed of Bs is independent from the speed of rotor.

[@ranarehman553]

Sir I got that, but the machine was intially operating as Generator and the voltage produced in generators is due go roataing magnetic field of rotor and the voltage in 3 phase coil has same frequency as rotating Br but now if we remove the prime mover shouldn't the frequency of voltage in 3 phase coil decrease and the corresponding speed of Bs ??

[@MAFarooqi]

The machine is connected to an infinite bus, and as soon as prime mover looses its energy, the machine starts working as a motor.

[@MAFarooqi]

If the generator would have been working standalone, the situation would have been the same as you have perceived. However, over here, the generator is connected to an infinite bus. As soon as prime mover is disconnected, the internal generated voltage drops and speed of the rotor decreases (during transients only), and the machine now starts behaving as a load (motor) for the infinite bus. Let me explain all the situation with the help of a very simple example. Suppose, you are riding a bicycle at some constant speed and suddenly you stop peddling. What will happen? Your speed will drop, however, your cycle is still supplying power (utilized to overcome friction). Now suppose another situation. You have tied your bicycle (through an rod, for example) to a truck which is running at a constant speed. As you peddle your cycle to run it at the speed of the truck, you are supplying power (energy). What will happen if you stop peddling in this situation? You bicycle will still run at the speed of the truck, however, it will now be working as a load for the truck (compare it with the earlier situation). So, your bicycle is analogous to the generator and the truck is analogous to the infinite bus.

[@muhammadosamaasghar9618]

@@MAFarooqi Excellent example sir...

[@mihiradeshappriya]

how Bs become Bnet?? At 10.10

[@MAFarooqi]

Explained at 15:42 in lecture at kzbin.info/www/bejne/fJ2aZ5mtp7yId7Msi=wFbt_NTRsOUK4p_-

[@mihiradeshappriya]

@@MAFarooqi Thx Sir

[@cupoftea411]

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