Testing a capacitor?
30 November 2012, 12:05 AM
#2
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30 November 2012, 12:21 AM
#3
If you don't have a meter, a rough and ready alternative test is to wire the cap up in a simple circuit and apply some voltage. 3 possible outcomes:
- if the cap is short, the fuse in your circuit will blow immediately.
- if the cap is open, when you try to short the cap with a light-bulb after cutting power to your circuit, the bulb won't light.
- if the cap is working normally, the bulb should light initially, then slowly fade.
- if the cap is short, the fuse in your circuit will blow immediately.
- if the cap is open, when you try to short the cap with a light-bulb after cutting power to your circuit, the bulb won't light.
- if the cap is working normally, the bulb should light initially, then slowly fade.
30 November 2012, 06:29 PM
#4
Remove capacitor, get a 12v battery. attach each end to the each terminal on teh battery.
Then remove capacitor from battery and place each capacitor lead on your tongue. Report your findings here.
If its a pure induction motor (i.e brushless) it is likely to be the cap as there is little to fail on them; just the cap, bearings and the windings.
If its a brushed motor then other things can go wrong.
If you know the cap size you maybe able to swap it with one on another appliance with a similar rating; A helpful Snetter told me my bench grinder would likely have the same capcitor rating as my tumble dryer motor...it did! Worked a treat too (had a few days without a dryers though until I sourced a new cap
)
Then remove capacitor from battery and place each capacitor lead on your tongue. Report your findings here.
If its a pure induction motor (i.e brushless) it is likely to be the cap as there is little to fail on them; just the cap, bearings and the windings.
If its a brushed motor then other things can go wrong.
If you know the cap size you maybe able to swap it with one on another appliance with a similar rating; A helpful Snetter told me my bench grinder would likely have the same capcitor rating as my tumble dryer motor...it did! Worked a treat too (had a few days without a dryers though until I sourced a new cap
)
30 November 2012, 07:54 PM
#5
you dont need to test it really. if the lathe works by giving it a little push, that confirms the cap is shot.
Just had a re-think !! 90% of the time it will be the cap.............................
Just had a re-think !! 90% of the time it will be the cap.............................
Last edited by albob; 30 November 2012 at 08:20 PM. Reason: a re-think..
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01 December 2012, 01:52 PM
#8
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Worth taking the old capacitor to the electrical supplier and asking them to test it before you buy another one.
Les
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