ECN Forum Forums General Topics of the Trade General Discussion Area Motor Starters

I am a bit perplexed! We wired 8 motors with IEC Motor starters, Start/Stop monetary switches all the same schematic they all work fine (except for one in which the contactor only locks on sometimes). Then we wired in another motor exact same schematic does not work. switched the starter still does not work. Someone eles wired it tied in the start/stop switches differently it works. I'm confused any ideas?

Check out the start/stop buttons. In a standard 3-wire control system, the start button should be normally open (contacts make when pressed) and the stop button should be normally closed (contacts break when pressed.)

If the buttons have the same operating/actuator hardware (trim, button, etc.) it is possible that they were assembled wrong.

Good luck.

Thanks for your reply it is working now with the same switch. and I tried reversing the connections still did not work

May have been phisicaly a bad fit for the coil,amature and or contactor body springs.(magnetic feild is stong enough to pull in but the springs cannot open the contacts)I've had this in a certain make of starter before where the fix was simply to take it apart and reassemble.Maybe a back feed from a control device.I always manually actuate the the starter 5 or so times while de-energized to see if its sticky.Hold open the stop pb while checking the coil for power if power is there and the pb is open it's a back feed on the control circuit see how the holing contact is wired.They can also heat up while energized and stick closed.

[This message has been edited by frank (edited 09-01-2005).]

I changed the starter and coil a few times already.

Sorry didn't read the post properly.Where in the circuit is it now wired?What type of machine and How many stop pb's Are they remote?Generally the stops are the very first device in the circuit.Sounds like the coil had A back feed and depending on how complex the circuit is one wire terminated in the wrong spot can do funny things down the line.It is also possible that they never found the problem an just wired around it.All you can do is keep going through the control circuit from the xformer to the coil as many times as it takes to find it.don't trust even your own wire numbers one small distraction can cost many hours frustration when you power it up.Is the panel fed from two sources?Are there dry contacts used from another circuit? If it isn't the starter its got to be the controls and moving the pb may just be hiding the problem.Hope all safeties and fail safes are still in circuit.Most importantly nobody can fix everything and like you i wouldn't let it go until i figured it out or had someone show me.
cheers

[This message has been edited by frank (edited 09-02-2005).]

each motor has its own circuit and starter. they are all wired independtly

So your saying the entire control circuit never leaves the panel?No remote pressure switches fail safes prox switches or dry contacts?What is this motor for?If the coil has power with the pb open the pb is not in circuit or the coil is tied to another intermittent cycling in phase source or back fed.Somehow the control circuit was parallel not series connected



[This message has been edited by frank (edited 09-02-2005).]

Could this be a Voltage drop problem?.

I thought that was the problem. The coils were 240v and the actual voltage was 208v
so I switched the coil to 208v still doesn't
work.