1. Visiting from the US? Why not try DIYnot.US instead? Click here to continue to DIYnot.US.
    Dismiss Notice

Electric Hoist Contactor issue

Discussion in 'Electrics UK' started by Bing, 17 Sep 2014.

  1. Bing

    Bing

    Joined:
    27 Apr 2004
    Messages:
    55
    Thanks Received:
    0
    Country:
    United Kingdom
    Hi all.

    I am currently working on a Machine that as an Hoist with separate raise lower Contactors. Whilst doing a load test on the Hoist, I noticed that when I manually activated the raise Contactor, on occasion the Hoist would actually lower the load momentarily. This is not a Brake failure, the Motor actually drives in reverse as if 2 of the phases on the Contactor had been swapped. If I wait a second & activate the same Contactor again, the Hoist raises. This isn't just when under excessive load, I have seen it do this without any load on it.
    Just to clarify, this as never happened during the machine's automatic running cycle, it as only happened when I have manually operated the Contactor through it's over-ride button on the front of the Contactor.
    I have never seen this happen before & am wondering if anyone can offer a technical explanation.
    Am I missing something blindingly obvious? Your thoughts please.

    Bing.
     
  2. Sponsored Links
  3. bernardgreen

    bernardgreen

    Joined:
    3 Nov 2006
    Messages:
    25,826
    Thanks Received:
    2,572
    Location:
    Bedfordshire
    Country:
    United Kingdom
    Maually operating a contactor by hand ( pushing in the actuator ) can result in the contacts not operating at the same time as each other. This may be resulting in one phase closing a short time after the other two and the motor may momentarily run in reverse as a result.
     
  4. Bing

    Bing

    Joined:
    27 Apr 2004
    Messages:
    55
    Thanks Received:
    0
    Country:
    United Kingdom
    Thank you for your explanation Bernard. That is what I kind of thought it might be, but just wanted some one else's take on it. That's the beauty of these Forums, you can bounce things around with others!
    Thanks.

    Bing.
     
  5. donrkebab

    donrkebab

    Joined:
    15 Apr 2012
    Messages:
    507
    Thanks Received:
    26
    Location:
    London
    Country:
    United Kingdom
    It is a brake fault. After any up or down operation the brake should automatically and permanently lock the hoist. And it should only release on new up or down movement.
     
  6. Sponsored Links
  7. JohnW2

    JohnW2

    Joined:
    28 Jan 2011
    Messages:
    48,635
    Thanks Received:
    3,189
    Location:
    Buckinghamshire
    Country:
    United Kingdom
    Yes, but if bernard's theory were correct, there would have been "new up or down movement" (to release the brake), albeit momentarily in the unintended direction.

    Kind Regards, John
     
  8. Bing

    Bing

    Joined:
    27 Apr 2004
    Messages:
    55
    Thanks Received:
    0
    Country:
    United Kingdom
    Thanks for the replies Donr & Jon.
    I did try to write my question as clearly as possible but it seems not clearly enough.
    I don't believe it's a brake problem because when the Contactor is released the Hoist stops immediately with 1500Kg load on it. It doesn't creep in the slightest & in fact the Brake was only adjusted 3 Month ago.
    This issue only happens when I manually over-ride the raise Contactor, more often than not it will lift rather than lower.
    I am quite happy with Bernard's theory but I am open to other views.
    Just to reiterate, the Hoist stops the moment the Contactor is released by the Brake, whether it has raised or lowered.

    regards.

    Steve.
     
  9. ericmark

    ericmark

    Joined:
    27 Jan 2008
    Messages:
    18,617
    Thanks Received:
    1,746
    Location:
    Llanfair Caereinion, Nr Welshpool
    Country:
    United Kingdom
    On manual operation is that still electrically activated or are you pushing the contactor with a screwdriver the latter is likely to close only two phases.

    Is it a three phase motor or is it single phase using a three phase contactor to energise start and run coils?
     
  10. Bing

    Bing

    Joined:
    27 Apr 2004
    Messages:
    55
    Thanks Received:
    0
    Country:
    United Kingdom
    Hi Ericmark.

    The Motor is a 3 phase Motor & yes, I am operating the Contactor over-ride button on the front, with a Screwdriver in the main Control Cabinet.
    From your reply & question, I am assuming that Bernard was right with his theory.

    Thanks for your input it is appreciated, everyone.

    Still learning after all these years!

    Best regards.

    Bing.
     
  11. DIYnot Local

    DIYnot Local

    Joined:
    3 Sep 2019
    Country:
    United Kingdom

    If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

    Select the supplier or trade you require, enter your location to begin your search.


    Are you a trade or supplier? You can create your listing free at DIYnot Local

     
Loading...

Share This Page