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    250VAC Run Motor Capacitor

    I know what capacitors do, in theory, but I do not have a real-world/application knowledge of (motor) run capacitors.

    I am replacing a 10uF +/- 5% 250VAC (motor run) capacitor that popped in my bench grinder. Man, did that bang scare me! I found, in my box of capacitors, the following new cap: 12.5uF +/- 5% 250VAC (Motor)
    (They are both big, cylindrical types, roughly 30mm diameter x 70mm height...roughly the size of the size D batteries)

    Can I use it? Is there a general rule-of-thumb to remember for such?

    The new one is the same as:
    http://www.westfloridacomponents.com...L-2EJ012E.html

    The old one just has the specs (I listed) & model #: CBB25
    (The only CBB25's I was able to find on the web were definitely different...miniscule capacitance & box-type.)
    Last edited by JuniperSprouts; 10-05-2012, 11:57 AM. Reason: added link for capacitor

    #2
    Re: 250VAC Run Motor Capacitor

    The general rule is replace with same uF value and equal or higher voltage rating. The 12.5uF will probably work fine but may make the motor run a bit hotter. You don't necessarily need the same part #, just a typical 10uF film cap in a size you can mange to strap on where it goes, and of course the right terminal type of you don't want to rig new connectors.

    Personally if the bench grinder isn't a high end/expensive model, I'd use the 12.5uF you already have, but ideally it should be another 10uF.

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      #3
      Re: 250VAC Run Motor Capacitor

      Look at this site they have one for about $7.50 the right UF value 10 uf @ 250 volts AC

      http://store.eurtonelectric.com/capa...0uf250vac.aspx
      9 PC LCD Monitor
      6 LCD Flat Screen TV
      30 Desk Top Switching Power Supply
      10 Battery Charger Switching Power Supply for Power Tool
      6 18v Lithium Battery Power Boards for Tool Battery Packs
      1 XBox 360 Switching Power Supply and M Board
      25 Servo Drives 220/460 3 Phase
      6 De-soldering Station Switching Power Supply 1 Power Supply
      1 Dell Mother Board
      15 Computer Power Supply
      1 HP Printer Supply & Control Board * lighting finished it *


      These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

      1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
      2 Hem Saw Computer Stack Board

      All of these had CAPs POOF
      All of the mosfet that are taken out by bad caps

      Comment


        #4
        Re: 250VAC Run Motor Capacitor

        You might also enquire at HVAC supply houses locally, 10uF motor caps are fairly common in HVAC systems though usually in 450V value, which of course will be physically larger. I was really surprised that I found one locally for only $8 or so the last time one crapped out on my A/C, and even more surprised when the guy who sold it to me turned out to be an old friend I hadn't seen in over 20 years.

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          #5
          Re: 250VAC Run Motor Capacitor

          Thank you for the input, guys.

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