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Understanding of capacitors

lilbell

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Hello, my new here. My name is Craig. I'm a surveyor for the Army Corp of Engineering. What I need an understanding about is. I was just recently giving a 60 gal Black max compressor with a craftsmen (I believe) 5 hp electric motor. It did not come with a capacitor or capacitors, not sure if I need one or two. It's a 220 volts I know im just don't know which ones I need because of my lack of experience with big compressors and what all it takes to get one running and keep it running. I am infact a fast learner and and get it together if I new which ones I needed and which wires to hook it too
 
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lilbell

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A careful study of the motor nameplate may answer your questions.
I'm sure it would, if like I said in my comment about not being "experienced" so even if I were to look at the plate, i wouldn't know what I was looking for which would make me STILL NOT be experienced. So I'm pretty sure the question stands, but thank u.
 

The Cobbler

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not sure capacitor ratings are on the motor plate. I don;t recall ever seeing any listed. sometimes bearing #'s are listed .
unless you can find something online or someone with the same motor, it may be a difficult question to answer
 

dogdog

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I'm sure it would, if like I said in my comment about not being "experienced" so even if I were to look at the plate, i wouldn't know what I was looking for which would make me STILL NOT be experienced. So I'm pretty sure the question stands, but thank u.
AC induction motor are most likely on that compressor that you have especially if it is a single phase 240V / 120V motor. ...
They will have a start cap , and/or a run cap (not all motor have run capacitors) ... they are different for each motor.. even if the same HP motor , it can be different sometimes.

There are calculators online and charts. but I have found them not too accurate at least when I compare to the motors I have, it doesn't come close.... so. ...

people here recommended you to read the name plate of the motor, sometimes they might have the info written, or google the parts websites and see if they have the run cap or start cap for your compressor/motor. that is what they mean.

in general the start capacitor will always be higher capacitance than the run capacitor... run capacitor are usually 45uf or less.
the run capacitor is design for continuous operation, while the start capacitor will be higher capacitance, will get disconnected by the centrifugal switch (a mechanical switch) inside the motor once it is spin up to certain speed, it is not designed for continuous power....

in general the ac capacitors are non-polarized, higher the capacitance bigger the size, higher the voltage bigger the size.

call the company, they should be able to look up your compressor and recommend a capacitor(s) for you.


This is a tidbit of info...if you have 2 capacitor motor.. run / start..
Both capacitor will be attached to the Run coil...
the start cap will be in series with the centrifugal switch.. the Run cap will be in parallel with the "start cap and centrifugal switch"

 
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