How to create pole in electric motor for speed variation?

WHEN THE MOTOR IS GOING FOR REWINDING ,AT THAT TIME ONLY THE POLES CAN BE CHANGED TO OUR REQUIREMENT.

THIAGARAJAN.E

The speed of a motor is a linear function of the [voltage applied on it's windings minus the (windings resistance multiplied by the current)] So you can vary the speed by varying the voltage. If you want a precise speed control, then you would need a feedback signal. You can use a tacho-meter which will give you a voltage output proportional to the motors speed. You can build a circuit which reads the tacho's voltage and varies the motor's windings voltage accordingly.

In general if you supply the DC motor with a PWM voltage, then the PWM's duty cycle would be proportional to the motors speed.

No one can create or add pole in existing motor. It is a designer part,provided as per speed required.

Well, Actually you can't add poles or decrease any ones since, each motor is already designed and constructed with that number. you can know which speed you can use depending on what you find on motor plate, as follows:

3000 rpm

1500 rpm

750 rpm

This means3000 rpm is corresponding to2 poles,1500 rpm is corresponding to4 poles.

because, the speed depends linearly & Reversely on number of poles, this means when number of poles increases to double, the speed decreases to half the speed.