capacitor for an electric motor?

[Soybomb]

I have a 120volt electric motor I need a 45microfarad run capacitor for. McMaster carr has one but its rated for 370V and is $23. They have one for 440V for $18 Will either of those work? I'm new to large AC motors so I don't understand how the voltage rating will come into play and thought maybe someone here would.

Thanks!

 

[Analog]

I am assuming that this is a 120 VAC electric motor?

Since it is single phase, it will need a start capacitor. Generally an electrolytic NPO will be sufficient, the 440V one is probably more common than the 370V, and that is why it is cheaper. You may want to check surpluscenter.com

Here is one for $1.49:
http://www.surpluscenter.com/i...&item=22-1092&catname=

 

[Soybomb]

Yup 120 VAC. So the voltage rating on the caps is a maximum and I could use higher if it were cheaper? "Requires a max 108uF start cap. and a 45uf run cap." I'm not too worried about the start cap, from what I understand most people using them in this application don't need the higher starting torque on the beefier start cap and for simplicity just go rith a 45uf run cap only.

This look good? http://www.surpluscenter.com/i...&item=22-1203&catname=

Even with shipping its probablycheaper than the mcmaster carr one.

 

[Analog]

should be fine, kind of overkill though?

 

[Soybomb]

Originally posted by: yellowfiero
should be fine, kind of overkill though?

How come overkill? 45mfd run cap as required.

 

[Analog]

Originally posted by: Soybomb

Originally posted by: yellowfiero
should be fine, kind of overkill though?

How come overkill? 45mfd run cap as required.

Because of the voltage rating. Most motors that run at high voltage don't require start capacitors, since they are 3 phase. Those higher voltage caps are generally used as power factor correction caps, but can be used for other purposes. In any case, its not that expensive to go with the one you want.