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Air Purifier Electrical Fault.

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I was given a faulty VAX air purifier to repair today. The fan would not turn. The motor would not work. The control buttons did operate and a confirmatory bleep could be heard when they were pressed. Also dim L.E.D.s lit up confirming that the control panel seemed to be o.k. The motor fan did rotate quite freely by hand. No damage to P.C.B. P.C.B. fuse o.k. The appliance is rated at 75 Watts. The 1.5 micro Farad motor starting capacitor was reading very low capacitance. In the pico Farad region. After replacement of the bad capacitor the motor still did not start.


What did I have to do to get the motor working, and why?


https://www.vax.co.uk/ap01-air-purifier

Z.
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    beeps suggest electronics, so there will be a relay or a triac that puts power onto the motor, presumably only when certain other conditions are met, but without knowing a lot more, we are in the dark.  Could be as simple as a cover interlock, could be fiendishly hard.
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    mapj1:

    beeps suggest electronics, so there will be a relay or a triac that puts power onto the motor, presumably only when certain other conditions are met, but without knowing a lot more, we are in the dark.  Could be as simple as a cover interlock, could be fiendishly hard.




    Thanks Mike. More clues. My component analyser identified a three legged device as a sensitive or low power thyristor. That seemed o.k. It connected to the capacitor start capacitor run induction motor. The motor would not run even with a hand "kick start". I believe the P.C.B. to be functioning correctly. There are no filter door interlocks or micro switches.  Just how warm does a stalled motor get?


    P.S. Mike, is a 250 Volt A.C. X2 type capacitor (WIMA MKS 4-R) rated at R.M.S. mains Voltage or peak Voltage?


    Z.

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    Zoomup:




    P.S. Mike, is a 250 Volt A.C. X2 type capacitor (WIMA MKS 4-R) rated at R.M.S. mains Voltage or peak Voltage?

     





    If peak voltage then 1.414 times. BTW fart dispensers are prone to sticky particles. 


    Jaymack

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     BTW fart dispensers are prone to sticky particles. 


    Jaymack



     




    What?


    Z.

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    I have found this reference source that discusses X ratings of capacitors.

    https://www.allaboutcircuits.com/technical-articles/safety-capacitor-class-x-and-class-y-capacitors/


    Z.
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    Indeed. An 'X' capacitor is rated to spend all day connected L-N, but is allowed to fail dead short - as the assumption is tht this trips the ADS and is safe.

    A Y capacitor has a higher standard, and is intended to be between Live and the case of earthed equipment, and is very care fully designed to fail open circuit when  it finally dies.

    Ratings are RMS, but there is a huge margin - a 250V X2 will have been tested to survive short duration 2500V  surges - the equivalent Y about twice that.

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    Thanks for that Mike. The problem was, as far as I can gather, that the capacitor went open circuit and the motor stalled. Perhaps it was turned on and left on but it didn't rotate the fan blades. As the unit is very quiet on the low speed the fault may not have been noticed. Then the motor overheated and the thermal fuse opened as well to reduce the chance of fire and further damage. I replaced the thermal fuse and the capacitor and oiled the motor bearings with thin synthetic oil, now the unit works well. Please see my other post about servicing a fan motor as it shows the thermal fuse renewal.


    Fan head motor servicing....https://www.youtube.com/watch?v=KtDz_GPIi0s


    The capacitor is the black box with two wires as seen in the video.


    Bye,


    Z.

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