Capacitors (running or starting)

Discussion in 'General Electronics Chat' started by peterangelo, Feb 12, 2012.

  1. peterangelo

    Thread Starter New Member

    Feb 12, 2012
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    hello,

    i have problem with my exhaust blower installed at our mini theatre. the blower rating is 450 watts, single phase (220-240 Vac), 50/60 hz. the blower was functioning normally but when fluctuation occurred the blower suddenly become weak. it can't extract heat already but it is running. i tried to checked the input voltage but it alright. i checked the capacitor, which i don't know if it is running or starting cap, but found out that it is far from its value. the cap value is 40microfarad but the reading was only 19 nanofarad. does this mean my cap is already defective or maybe there's something wrong with the motor windings?
     
  2. crutschow

    Expert

    Mar 14, 2008
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    Did you disconnect the cap before measuring its value? If it is indeed only 19nF then it is likely bad.
     
  3. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    U have a defective starting cap.
     
  4. peterangelo

    Thread Starter New Member

    Feb 12, 2012
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    yes. i removed the cap before measuring it. there's only one cap in there but i'm wondering if it is a running cap or starting cap.
     
  5. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Starting ...
     
  6. shortbus

    AAC Fanatic!

    Sep 30, 2009
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  7. PackratKing

    Well-Known Member

    Jul 13, 2008
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    I will concur w/ Shortbus........it is a run cap.

    Be sure to perform any more testing on the ductwork the unit is normally mounted on, as the amp draw of the motor will be excessive if operated in free air w/o its baffles.

    Excessive to the point the motor will cut out on its internal thermal overload, and will very soon begin to lose the magic smoke it works on :D if it hasn't already.
     
  8. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Funny... If it was one cap, It was always starting.

    Atleast that's all I have seen here so far.

    If there were a running one, it would have two of them.

    Guess I was wrong. Or am I?

    {ED}

    Hey I was right somewhat..They are dual caps.

    So it was the running one that faulted.
     
  9. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Check out our Ebook - http://www.allaboutcircuits.com/vol_2/chpt_13/9.html ,look for "split-capacitor" motor. This motor type has no start capacitor, just a run cap. This is often used for fans and blowers.

    What your referring to is a 'capacitor start - capacitor run' motor, not the same animal.:)
     
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