# Help on Capacitors

Discussion in 'General Electronics Chat' started by daza1970, Sep 7, 2014.

1. ### daza1970 Thread Starter New Member

Sep 7, 2014
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Hello new in here just surfing for help and came across this site. So I was wondering if you could help me??
I have a single phase motor 3ph 240 volt which is not running. It has a run (50 u ) and a start capacitor (200u) I have tested both capacitors. Tested with an analogue meter ( 1k ohms ) the run capacitor flicks over and returned to 0 but the start capacitor files over and sits 1/4 of the way up the gauge.
So the question is, is the start capacitor no good or is it the motor?

2. ### profbuxton Member

Feb 21, 2014
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New capacitor needed!

3. ### daza1970 Thread Starter New Member

Sep 7, 2014
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I don't have one that big. Can I link 3 or 4 together to get the 200u needed ?

4. ### daza1970 Thread Starter New Member

Sep 7, 2014
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Sorry just to test before I by a new one?

5. ### ISB123 Well-Known Member

May 21, 2014
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Example:

3 Caps in parallel equal 300uF since they add to each other,in series they are dividing.

Series formula:

Parallel:

Last edited: Sep 7, 2014
6. ### daza1970 Thread Starter New Member

Sep 7, 2014
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I have tried to put a 50 u in and did not do anything. I take it that the motor is N/G.

How would I check this?
There are two wires running into the motor. One is the n and the second comes from the starter capacitor.
The second set of three wires, One from the start capacitor and two from the run capacitor.

As you have guessed by now electricity is not my strong point.

7. ### ISB123 Well-Known Member

May 21, 2014
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For how much Voltage was the capacitor rated(VAC)? The 50uF one you used.

8. ### andrewmm Active Member

Feb 25, 2011
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The motor capacitors are normally in my experience quite 'big' things, designed to take the high Di/Dt current spikes. you could put 100 uf of ceramic on, but I dont think that would work. For safety, you need the same type of capacitor, used to be paper, .. watch out for the voltage ratings . what was the old one 600 Vdc , 400Vac ?

the capacitors get hot with the current flowing in and out, which is why they degrade over time.

9. ### Electric Al Member

Nov 6, 2013
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(I have a single phase motor 3ph 240 volt)

I think you mean a single phase 3 HP motor !

Just trying to avoid confusion !

Sep 7, 2014
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