Rewinding AC Motor

<...how to find out KW of an motor by seeing it...>

The original equipment manufacturer's rating plate gives the size, voltage, frequency, power rating and other useful data. The plate is attached to the motor at the final stages of manufacture and testing.<...what is the priciple behind winding...>

The windings produce the magnetic fields that enable the motor to turn.

<...a single phase A.C motor...rewind it...>

Why is this motor to be rewound? Has it burnt out? If so, then rewinding it will not solve the real problem.

<...what will happen if ...reduse no. of turn...>

Why must the number of turns be reduced? Why is the motor manufacturer's design to be compromised in this way? What qualifications and experience does the rewinder have of carrying out this operation?

-o-o-o-

Why is a motor rewind preferable to a motor replacement? After all, the replacement comes with the manufacturer's warranty, and would make rewinding the original unneccessary!

Then the motor is not suitable for any purpose that requires a high level of confidence in its performance.

Replace it and scrap the original.

Hello howrang bajaj

1. It is always best to place exactly the same number of turns with the same gauge wire as the original. The original designer and maker of the motor did know best.

2. If you reduce turns, you will increase current, and probably burn out your rewind job.

3. Find out kW of motor by reading the original nameplate. That's the best way, because that will have Volts, Amps, kW/HP listed, then you are certain what you have.

Unless the motor is a larger one, ³/₄ HP = 0,5kW or more, it is presently not economic in most locations, because a new motor made in either India or China is cheaper than the cost of the winding wire.

Of course, after you have carefully examined the old motor, taken careful notes re the windings, cut the wooden wedges, and slot insulation, rewound it, varnished it with Glyptal resin, replaced the bearings, replaced/repaired the centrifugal switch, connected it up to the power, and it works properly, you will certainly have a pride in your repaired motor, and that's a new-found skill for you too.

Kind Regards....

See #5.

Figure out the load requirements of what you are turning. Size motor, purchase new motor that will meet your torque/speed requirements. Make sure the motor will fit in it's new place. If you don't have nameplate data I would be leery of rewinding the motor yourself. And as has been stated earlier, if it's not a very large motor, you are better served by purchasing a new motor.

Nice description. thanx from up over

Single phase AC motor with Split phase principle { With Capacitor } works .

For reduced turns , speed will also go down .

KVA rating with power factor [ As as average 0.8 } getting multiplied - gives KW .

Hello sivaa

A single phase "split-phase" squirrel-cage motor speed is determined by the number of Poles, not by the number of turns of winding wire.

Sometimes these motors use a "capacitor" start for boosting the start-up increase from stop to full speed, against a higher load.

The number of turns on each pole determines the operating voltage of the motor.

The size of the wire determines the Amperes which flow, the consequent magnetic flux induced into the rotor, and thus the amount of actual work in kW/HP the motor can actually do, before it drops out of the area of: Synchronous speed less the slip speed = Rotational speed.

Trust that assists you.

Kind Regards....

how many slots does the stator have ?

what is the inside diameter of the stator and the length of the magnetic core ?

how many poles or what speed does the motor run ?

What diameter is the cupper wire ? wire gauge ? (the wire inside the motor and not the connection wire)

most regards

4 slots, 4 poles, 50mm dia of stator & 14mm side of cupper wire, 1400 rpm

Hello again, howrang bajaj

That measurement of 50mm dia. of stator sounds as if the motor came from a small household fan, probably around 250mm or 300mm diameter fan assembly.

Is that 50mm diameter the internal diameter or external diameter of the stator?

Alternatively, your 50mm dia. stator measurement is incorrect.

14mm size copper does not sound very likely, perhaps that measurement is not correct.

Is there still copper windings (burnt out, perhaps) on the stator?

What is the shaft diameter?

What type of bearings are used?

It looks as if the motor is for 50Hz mains frequency, and running speed would thus be between 1400 RPM and 1485 RPM, as it is probably a Squirrel Cage Rotor - Advise if the rotor is wound with winding wire, and/or has brushes to a commutator, please.

A motor of this type and size is not worth repairing, except in case of a part-numbered motor which is part of some specialized larger apparatus (but not a motor for a household fan).

Reply here, with

Kind Regards....

I agree with Sparkstation. Just the size of the motor makes it so that it is MUCH cheaper to just buy a new motor. If this is not an option, take it to a motor rewinding shop, they can usually duplicate number of turns and wire size fairly easily if they are competent.

If you see them checking motor rotation with a ball bearing, they aren't competent.