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Discharging and testing 2 large capacitors

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Carsey:
Hi

I have 2 large capacitors which I need to remove and test from a wood working machine (Electra beckum hc260 motor) which is blowing plug fuses when we try to power it on.

I have just bought a amecal st-9927t meter in hope of measuring the capacitance to hopefully identify a issue with the start and running motor capacitors.

Does anyone have any advice how to safely remove and test the capacitors to avoid any risk of shock?  They are pretty big in physical size and look like they could deliver a bit more than a tickle.

I’ve attached 2 pics of them below with their specs on.

Any advice would be appreciated and/or any clues why our plug fuses 13A keep popping when we try to run the machine motor.

Thanks

Chris

SeanB:
Simplest check is to use the capacitance range on the meter and measure them. Short the 2 leads on the capacitor forst to remove any charge, but as you have them off anyway there probably is none. Reading should be over 45uF for them to be functional, and the simplest is to replace them, motor run capacitors of 50uF are a common value, and you get them with wire leads like that very easily from most large electrical wholesalers as well, or from any industrial motor supplier.  Them going low value will result in the motor not starting, and blowing fuses, though first check, with the power disconnected, that the motor does turn freely. if the motor start capacitor is open the motor will try to start, and as it does not turn fast enough to disconnect the start switch it blows the fuse. Same if the start contacts are sticking for some reason as well.

Carsey:
Thanks for your reply.

Is shorting the wires together on the end ok or best done with a insulated screwdriver?

The motor does turn freely as this was one of the first things I checked when it failed to start.   Can can actually hear it hum for a split second then the fuse goes.

Is it just a case of checking both the capacitors once they are off the machine? 

I did read on another forum about there being contacts for the start switches but the motor seems a sealed unit with just a fan on the end so cant see anywhere can check any bushes that could be stuck or sticking.

SeanB:
Just short them together with power unplugged, it will be fine here.  Hums then pops the fuse most likely the capacitors are either low or open circuit. Does the motor turn over at all in that brief period.

Carsey:
It turns over about a partial turn but no where near a full rotation.  1/32th of a turn at most!

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