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Motor Keeps going after it's turned off.

Discuss Motor Keeps going after it's turned off. in the Commercial and Industrial Electrical at Tilers Forum; Newman 3 phase induction motor (Bradbury liftmaster MK1) on a four post ramp - . When the ramp is raised it sometimes keeps going - bloke says he can't switch ...
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    Default Motor Keeps going after it's turned off.

    Newman 3 phase induction motor (Bradbury liftmaster MK1) on a four post ramp - . When the ramp is raised it sometimes keeps going - bloke says he can't switch it off by regular switch - has to do it at the main isolator. I haven't been there yet, any ideas?

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    Default Re: Motor Keeps going after it's turned off.

    Contactor sticking?
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    Default Re: Motor Keeps going after it's turned off.

    Poor connection on the contactor which is making it stick might have to change the contactor or strip it down and clean the points of contact with some fine emery paper if it's the old open type.

    Check to see if the push button is ok, should be have a contact coil on it, but could still give you problems.

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    Default Re: Motor Keeps going after it's turned off.

    Also could be the raise button sticking? Maybe the contol box needs the buttons and the contacts behind them cleaning and re-assembling

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    Default Re: Motor Keeps going after it's turned off.

    If it was a sticking raise PB then the raise would cut back in when power was restored.
    Does it have a stop PB? Most don’t, you normally have to keep your finger on the PB as a safety precaution.
    Will have to think about this one.
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    Default Re: Motor Keeps going after it's turned off.

    It looks to me as though the action of turning the isolator off is dropping out the raise contactor,so I'd guess it's a control issue (which I think we've worked out already!!!).
    How does the lift work?motor up and down or does the motor power a hydraulic lift then it just releases the pressure to lower it?

    My one was electric power,hold the button in then release wherever up and down.

    A lot of them are very crude,literally the push button has a plastic stalk on the back that pushes the contactor in physically to operate it,usually interlocked then to prevent arcing if up and down are operated simultaneously. I'd go for jonboy's idea of a good physical clean up first,something sticking etc.

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    Default Re: Motor Keeps going after it's turned off.

    Quote Originally Posted by malcolmsanford View Post
    Poor connection on the contactor which is making it stick might have to change the contactor or strip it down and clean the points of contact with some fine emery paper if it's the old open type.

    Check to see if the push button is ok, should be have a contact coil on it, but could still give you problems.
    Far better to clean contacts with ''Glass Sticks'' (glass-fibre strands held tightly together by glued fibre tape, or in a purpose made height adjustable pen type construction) The finish is as good as a new contact surface. I haven't used fine emery paper for maybe 25 years now... You can purchase from any good electronic stores, or where i get mine from, RS.

    Yes the fault could well be in the push-button, the contacts within the push-button unit could be stuck/wedged in the contact position while the spring release is still sending the button back to it's normal position, making it seem like it's working normally.
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    Default Re: Motor Keeps going after it's turned off.

    Thanks all - as stated - contactor sticking - lift installed 1964 and some very crude switching via pulleys and springs etc. all surrounded by hydraulic fluid and, filth!

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    Default Re: Motor Keeps going after it's turned off.

    Quote Originally Posted by eddybs23 View Post
    all surrounded by hydraulic fluid and, filth!
    Always a good combination.

    Well done and thanks for getting back to us.
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