Why capacitor used in single phase only?

It can be also used in three phase system, to correct the power factor of the three pahse distribution system..

Many single phase motors use a capacitor for starting. I don't remember just why. Back a while ago, tkrussel posted a link to a very exacting explanation in the E&L forum. The search feature works well here, if you can come up with the right key words, you may find it.



I am going to suggest moving this to E&L where he may see it and remember the link to post again.

3 phase power factor capacitors are an entirely different matter. 3 phase motors run fine without them.