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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    0
    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
    233
    68
    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
    5
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    Sorry just to test before I by a new one?
     
  5. ISB123

    Well-Known Member

    May 21, 2014
    1,239
    527
    Example:

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


    Series formula:
    [​IMG]

    Parallel:
    [​IMG]
     
    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
    1,239
    527
    For how much Voltage was the capacitor rated(VAC)? The 50uF one you used.
     
  8. andrewmm

    Member

    Feb 25, 2011
    29
    6

    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
    58
    8

    (I have a single phase motor 3ph 240 volt)




    I think you mean a single phase 3 HP motor !

    Just trying to avoid confusion !
     
  10. daza1970

    Thread Starter New Member

    Sep 7, 2014
    5
    0
    Thank you for your correction.
     
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