Most smaller, single phase motors usually have a permanent magnet armature that is pushed / pulled around by the rotating inductive field produced by the stator (outside) windings. The inductive field rotates simply as a result of the positive / negative alternations of the 60HZ AC current flowing through the windings. The problem is that when the voltage is applied, the 60HZ is applied immediately, the rotation of the field through the windings begins immediately, and the armature has no chance to react (or catch up, as it were) to the field.

The start cap provides that electrical "push" to get the motor rotation started. It does this by creating a current to voltage lag in the seperate start windings of the motor. Since this current builds up slower, the armature has time to react to the rotating field as it builds up, and to begin rotating with the field. Once the motor is very close to it's rated speed, a centrifugal switch disconnects the start cap and start windings from the circuit. Watching a single phase motor starting you can see that this all happens very quickly.

Without a start cap (such as when one burns up) when the voltage is applied, the motor will just sit and hum. But if you were to grab the shaft and give it a spin, the motor would (usually) start and run normally.

hope this helps,...

Hi I got an air pump and motor that is belt driven for an air compressor I rigged it to work with an old tank and automatic shutoff valve and everything work, my question is how come my electric motor doesn't have a capacitor?

 

I guess it is either an universal motor or a three phase motor.

 

I guess it is either an universal motor or a three phase motor.

Or a shaded pole or polyphase induction motor.

 

It's a standard induction motor. Not all designs need a start capacitor to work.

If the start winding is wound with a smaller gauge wire with a considerably higher resistive than inductive values than the main run windings it will create a offset phase lag just like a capacitor start motor uses to get going.

 

@Dpinedo1 I would like to know where you saw this??

Most smaller, single phase motors usually have a permanent magnet armature that is pushed / pulled around by the rotating inductive field produced by the stator (outside) windings.

Max.

 

What does it matter? It's simply not true.

 

What does it matter? It's simply not true.

Obviously , Just could not see a member of this name or the OP.
Max.