what is the difference between synchronous and asynchronous motor?

Question

i want the difference in working operation at the rotor side as at synchronous motor rotor feeded by D.C current but at induction by A.C

Answer 1

A "machine" has a shaft for rotational energy input/output and electric terminals for electric energy input/output. If it takes electric energy, it is "motoring;" If it gives electric energy, it is "generating."

A synchronous generator rotates an electromagnet within coils generating three-phase alternating current. All by itself, it is not "synchronized" with anything.

So let's have two steam-turbine synchronous generators put in parallel, with both turning at 3600 revolutions per minute (rpm). Now, the generators must both turn at the same speed. If one loses steam completely, it will motor at
3600 rpm pulled along by the other generator working harder. But let's put the steam back, and have the two turning as generators. The point is, either machine can only generate or motor at 3600 rpm.

Picture a third synchronous generator with a diesel engine attached as a potential prime mover. I must start the engine and have it turning at 3600 rpm before I parallel this third machine. If I feed enough fuel, it will join the
other steam-powered generators and share the load at 3600 rpm. This is the synchronization aspect. This "doubly-excited" machine (DC on the rotor; AC on the stator) can only participate in average energy conversion at 3600 rpm. It must be synchronized.

Can we parallel a fourth machine that does not have to be synchronized? Yes. I attach a two-pole squirrel-cage induction motor to another
prime mover -- this time, a windmill propeller.

I parallel the four machines, and the induction motor begins spinning the propeller at a speed less than synchronous speed -- say, 3200 rpm. The induction motor is acting as an asynchronous motor. Suddenly, the wind picks up big time, and the propeller, instead of taking energy, begins pumping mechanical energy into the motor. Now the speed is 4000 rpm, and the induction motor is now acting as an asynchronous generator. Any speed above 3600 rpm will result in generation.

Being singly excited (AC on the stator) allows the induction machine to generate or motor at any speed. Above 3600, it generates. Below, it motors.

There's your asynchronous generator. But it must work with other machines, at least one of them one that is doubly excited.

Answer 2

Synchronous Vs Asynchronous Motor

Answer 3

I really like teressa's answer - very long and complete.

In short synchronous motor's run in lock step with the rotating magnetic field produced by the AC field winding. There may be a phase difference - lead or lag, however the frequency with which the rotor spins is locked to the frequency of the AC power.

Asynchronous motors run at a frequency not locked to the AC power, either faster or slower depending on whether power is being generated or used.

Answer 4

This Site Might Help You.

RE:
what is the difference between synchronous and asynchronous motor?
i want the difference in working operation at the rotor side as at synchronous motor rotor feeded by D.C current but at induction by A.C

Answer 5

Synchronous AC motors run at a speed fixed by the input line frequency. Typically 60 Hz in the USA. Run a clock with the sync motor from the USA in England and it runs slow because they use 50Hz.

Asynchronous motors run at whatever free-run speed they feel like, and slow under load. A DC wound hand-drill is such a motor, runs pretty fast till you start drilling, then it slows down.

A synchronous motor will develop maximum power at its' designed speed, try to slow it down and it puts out more torque. Slow it down by overload, it doesn't create more power, it just creates more heat.
An Async motor creates highest torque at stall speed, least torque as it approaches maximum speed.

https://www.electrikals.com/products/rm-motors/havells?mid=28&cid=641&page=1&pagesize=20

Answer 6

Maybe so

Answer 7

thankyou for the answers, very much appreciated.