Why we use capacitor with monophase motor? Is there specific reason? If it possible to have some diagrams to understan the operation of capacitor when it is connected to a monophase motor.

Thank you everyone in advance
Any help will appreciate!!!

 

Hi, This capacitor is needed to develop starting torque. In fact an monophase motor has two windings - one connected directly to net and second in series with capacitor. Basically this creates so-called elliptical rotating magnetic field instead of pulsating. As to keep motor running once it started pulsating field is enough then the second winding with a capacitor is being disconnected.

Regards,

Jacek Dobrowolski, Ms. Sc. E. E. Software Engineer

 

Hi there,

Why we use capacitor with monophase motor?

Ever tried to disconnect the capacitor? If you should disconnect the capacitor your motor won't turn. In other words your motor axle is standing still. The capacitor creates the elektric turn field that makes your axle turn.

Bye

 

A monophase voltage has no rotation direction (unlike a 3 phase which has). Without at least 2 phases, a motor (asynchronous, i.e., squirrel cage) wouldn't know in which direction to turn. An auxiliary winding fed by a capacitor that shifts the voltage in phase versus the main winding creates an artificial 2nd phase that start turning the motor in a particular (rotation) direction. In some applications, the auxiliary winding continues to operate after that motor picked up speed, in others, it is cut of by an internal centrifugal switch. Meir

 

I assume you are not an electrical guy
So In simple language....
The conventinal three phase motor has three separate windings and supplied with a three phase power. the currents are displaced at 120 deg apart,the magnetic field produced by these currents are also120 deg apart. so a rotating magnetic field is produced.And this pulls the rotor and motor rotates.
In case of a single phase there is no such thing.So motors designed for single phase are provided with two windings. One winding is connected directly to the supply and the other by a suitable capacitor connected in series also connected to the supply. The current in the capacitor connected winding will have it's current lead by approximately 90 deg and the magnetic fields produced by the two windings are also 90 deg apart.A rotating magnetic field is produced now and So the the motor starts to run.
There are other variations in these design like using bigger capacitor in the starting time and a smaller capacitor (or no capacitor and no current in starting winding) during running etc. For further knowledge you can refer some good electrical book.
regards,
Sekar

 

You did not say what kind of motor us a using. I assume you are talking about an AC inducion motor
such as a fan motor. Monophase motors must have some
means of generating starting torgue. Many motors are
wound with a 2-phase winding and a capacitor is used in the circuit of one of the windings to produce a phase shift in the current. Some motors remove the capacitor and 2nd winding after starting an others run with 2 windings and a capacitor. These are knowen as permanet split induction motors.

 

what is a 2 pole single-phase motor?