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Thread: Contactor Question

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    Contactor Question

    Today i replaced the switchgear on a star delta circuit. Simple enough ....
    When i pressed start nothing happens. So i realized my coil voltage was not right. So i took the old coils and put them in the new contactors.
    The first question is would it damage a contactor or its coil if i gave it 110V on a 22Ov coil? I'm thinking no???
    So then the circuit works after the change exept when delta pulls in the contactor chatters and shakes heavy before it pops the fuse on the transformer. So what could cause this?
    Nothing wrong with the wiring because when i put the old contactor back it worked fine.
    So it could be the coil but it was working an hour before i started, only thing i can think of is that it might be a dud contactor? is that possible?

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    Diamond Member AndyD's Avatar
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    Dud contactor is a long shot but it's possible. The phrase '.......but it was working an hour before i started' would be the hint of a more likely cause, check the circuit you've worked on and every termination.

    110v across a 220v coil won't cause a problem for the coil, it's more likely to cause burning or arcing at the actual load contacts due to slow and sluggish operation.

    In general a contactor that has sufficient voltage to bring it in will stay in without chattering. The voltage required for it to operate from scratch is higher than the voltage required to hold it in once it's operated. Chattering is more likely to happen if there's a poor connection, or incorrect wiring where the coil supply is being interrupted due the the operation of the contacts. Possibly specifying a contactor with a normally closed aux contact instead of a normally open one or vice versa but this would be obvious with the contact numbering.

    The only other thought I had was that you should check to see that the coils is AC rated not DC but this is a more common issue with 24volt coils than 220 volt ones.
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    Site Caretaker Dave A's Avatar
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    The other reason for chattering could be a voltage drop when the load comes in...
    The trouble with opportunity is it normally comes dressed up as work.

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    the delta contact on the timer could be damaged, or the n/c on the star contactor . connect 110 volt direct on to the coil and see if it works. hope you have mechanical interlocks.it could be expensive if both come in at the same time.

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    Gold Member Martinco's Avatar
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    I have experienced this before and what happened when I stripped the top of the contactor to replace the coil, I inadvertently rotated the top part by 180 degrees which caused the mating surfaces on the core to be 180 degrees out. I can only assume that the copper strips embedded into the laminated core had something to do with the chattering of the contactor.
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    Quote Originally Posted by Gei View Post
    Today i replaced the switchgear on a star delta circuit. Simple enough ....
    When i pressed start nothing happens. So i realized my coil voltage was not right. So i took the old coils and put them in the new contactors.
    The first question is would it damage a contactor or its coil if i gave it 110V on a 22Ov coil? I'm thinking no???
    So then the circuit works after the change exept when delta pulls in the contactor chatters and shakes heavy before it pops the fuse on the transformer. So what could cause this?
    Nothing wrong with the wiring because when i put the old contactor back it worked fine.
    So it could be the coil but it was working an hour before i started, only thing i can think of is that it might be a dud contactor? is that possible?
    are you sure the n/o and n/c contacts on the control circuit are the same

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    Thanks for all the replies, Found where i made the mistake, When i stripped the contactor to change the coil the iron core that holds the coil in place fell out and i did not notice this. Found it the next day on the floor. This will teach me to strip the thing while its still mounted in the panel with wires attached. To much of a rush and to lazy to take it out. Cheers

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    Diamond Member AndyD's Avatar
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    Thanks for the follow-up, it's always interesting to find out what the problem was in the end.
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