start stop interlocking

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rjdad82

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Having a bit of a brain cloud....i have seven motors all on starters with start stop buttons. They all have low voltage xfmrs for the control voltage. Right now they all work independently. I have to interlock all the motors together in sequence so that they can be turned on in order 1-2-3-4-5-6-7 without either being able to be turned on without the previous. my cloud is where to hook in the interlock wire so that the next start button can be used after the first. thanks for any input.
 

iceworm

Curmudgeon still using printed IEEE Color Books
Location
North of the 65 parallel
Occupation
EE (Field - as little design as possible)
Wire an Aux NO contact from the first starter into the STOP circuit of the second starter. Wire an Aux NO contact from the second starter into the STOP circuit of the third starter.

You get to fill in the rest.:)

Of course if motor 1 is turned off, then all stop, #2 next, then #3 ..... to #7, one relay click apart.

the worm
 

Ken9876

Senior Member
Location
Jersey Shore
You?re probably going to need several auxiliary contacts one per motor starter except for the last one. So your control circuit for motor two would first be feed through the auxiliary contact on motor one which would be held closed as long as that starter was energized
 

rjdad82

Member
I was bringing the NO from the first to the STOP of the next but took out the link from the existing start to NO ... .... brain cloud ... thanks again for the help.
 

hurk27

Senior Member
Having a bit of a brain cloud....i have seven motors all on starters with start stop buttons. They all have low voltage xfmrs for the control voltage. Right now they all work independently. I have to interlock all the motors together in sequence so that they can be turned on in order 1-2-3-4-5-6-7 without either being able to be turned on without the previous. my cloud is where to hook in the interlock wire so that the next start button can be used after the first. thanks for any input.

No aux contacts needed, just remove the control voltage supplying the stop button for contactor 2, and supply it from the coil from contactor one, again supply 3 from 2's coil and so on, but if any overloads trip any contactor after that point will also de-energize, with the aux method same thing would happen anyways.

IF this is a problem then start button would be fed from the previous coil, but the stop and hold-in contacts would have to be fed from the control supply, this way only the start button has to be done in sequence but the hold in will keep working for all the starters but the one with a tripped OL.
 

hurk27

Senior Member
Thanks so much guys for the insight i think i have got it now, thanks for your time.

Your more then welcome.

If you need all motors to stop in the event of one motor failure, then series all overloads then feed the L2 side of each coil from the end of the last overload, this will drop out all the contactors if one over load trips.
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
Your more then welcome.

If you need all motors to stop in the event of one motor failure, then series all overloads then feed the L2 side of each coil from the end of the last overload, this will drop out all the contactors if one over load trips.

One other thing to be aware of: With Hurk's diagram, if someone stops motor #4 (just as an example), motors 5, 6, 7, and 8 can still run. That may or may not be OK.
 

rcwilson

Senior Member
Location
Redmond, WA
Daisy chaining the coils as suggested means all the contactors will be powered off of one control power transformer. That will probably overload the transformer and may pop the fuses when the last few motors come on.

If it was my plant I would want the control power for Motor 2 to only come from its MCC bucket and not Motor 1. Go with the Aux contacts.

What if motor 4 trips its CB in the MCC. The contactor will still be held in because the power is from the previous motor. Motors 5-8 will not stop.

This logic is common in a converying system where the downstream conveyors need to run before the upstream one starts to prevent lgojams. When a downstream conveyor stops alll the upstream ones need to halt also, otherwise product gets damaged as it's pushed onto a stopped conveyor.
 
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
Wire an Aux NO contact from the first starter into the STOP circuit of the second starter. Wire an Aux NO contact from the second starter into the STOP circuit of the third starter.

You get to fill in the rest.:)

Of course if motor 1 is turned off, then all stop, #2 next, then #3 ..... to #7, one relay click apart.

the worm

This is probably the most common method but I have also seen it done by inserting the Aux NO into the Hold portion of the next control. Troubleshooting was initialy a real pain until we realized that this was not an "Oops" or a shortcut but planned. However you do it, leave a drawing around somewhere. Just because you know, doesn't mean the next guy will.

Next thing is to spend the bucks & buy yourself a CLICK plc and start playing. Add one of their low end HMIs and for -$300 you have yourself a learning tool.
 
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