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Participant

Join Date: Feb 2008
Posts: 1

Troubleshooting a Magnetic Contactor, Overload Relay, and Push Button?

02/21/2008 5:02 AM

i tested it using a multi tester and all deflected but when i applied current it didn't run. im fresh grad and this my first job. anybody? thanks!!!!

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Guru
Popular Science - Weaponology - New Member United Kingdom - Member - New Member

Join Date: May 2007
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#1

Re: how to troubleshoot a mgnetic contactor, overload relay, and push button?

02/21/2008 7:35 AM

Easies way is to fault find by substitution. Put in a 'known good' unit, if this works then leave it in place and take tha faulty unit back to your bench where you can play and learn in comfort.

Del

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Guru
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#2

Re: Troubleshooting a Magnetic Contactor, Overload Relay, and Push Button?

02/21/2008 1:31 PM

What did not run. Need more info. When you pushed the button did the coil on the magnetic starter draw in. If it did then check input and the output voltage of the starter. If you have good voltage out the problems else where. If you have good voltage in and bad voltage out the there is something wrong with the contacts.

I have seen where the contacts have carbon up from burning off environmental contaminates. Would test okay until you place a load on them. The resistance at the carbon build up would burn an open.

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#6
In reply to #2

Re: Troubleshooting a Magnetic Contactor, Overload Relay, and Push Button?

03/07/2008 1:45 AM

"What did not run. Need more info. When you pushed the button did the coil on the magnetic starter draw in. If it did then check input and the output voltage of the starter. If you have good voltage out the problems else where. If you have good voltage in and bad voltage out the there is something wrong with the contacts.

I have seen where the contacts have carbon up from burning off environmental contaminates. Would test okay until you place a load on them. The resistance at the carbon build up would burn an open."

In cases where you have seen the carbon issue you spoke of, did you also notice gritty material below contacts? I have this issue in several electrical cabinets. I assumed it was some sort of degradation, but not certain.

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Power-User

Join Date: Aug 2007
Location: San Francisco Bay Area
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#3

Re: Troubleshooting a Magnetic Contactor, Overload Relay, and Push Button?

02/21/2008 7:17 PM

Based on your description it sounds like you are dealing with a typical motor starter.

Look at your schematic. Verify control power (volts) is present.

Many circuits will put fuses feeding the contactor for instananeous protection and overload mounted below for long time protection. Verify you have proper volts at the line side of the contactor phase-to-phase.

The coil of the contactor should be wired through the trip contacts of the overload device. Verify it is not tripped (or miswired-if this is new).

E-stop circuits have taken out many a fresh tech...

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Commentator

Join Date: Feb 2008
Posts: 59
#4

Re: Troubleshooting a Magnetic Contactor, Overload Relay, and Push Button?

02/22/2008 8:14 AM

Did you check for the continuity or for the voltage with your multimeter? Best way to certify your circuit would be to deenergize it and check for continuity between the control circuit neutral and the "hot " side of the coil (if it's not apparent which is the "hot" side then check both sides of the coil), if your ciruit including the TOL relay and coil is good then you will read continuity on your meter. Apply voltage to the control circuit and push the start button. If the contactor is held in and motor still doesn't run then either the motor is defective or the power wiring (not the control wiring) is bad. While the contactor is made up, check to see if you have a voltage drop across it's (the contactor's) contacts. This will check the condition of the relay's contacts (any voltage present will indicate bad contacts). Also if you're missing a phase (single phasing) you will see it at the relay's contacts. Good luck!

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Active Contributor

Join Date: Dec 2007
Location: Auburn, MA USA
Posts: 23
#5

Re: Troubleshooting a Magnetic Contactor, Overload Relay, and Push Button?

02/22/2008 9:03 AM

Worked on many a starter. Make sure you coil is good, check res with your meter making sure you lift one lead as not to read thru your control trans an open overload conact may also be your problem should be N.C. with your heaters installed and reset.

1-Check and make sure your coil is not open-remove from ckt.

If your pulling a bucket from a MCC and it contains it's own control trans make sure you disconnect it.

2-Check your over load contcts making sure they are closed heaters installed and reset these feed the common side of your coil.

3- If you have the cheap IEC type with the "DIAL-A-AMP" setting they use bi metal heaters you could have one phase or more open and the over loads will not trip and when you put the starter in service you will single phase the starter and the unit will trip off the good phase.

4-If heaters are liquid filled make sure all the ratchets (weels) are solid ( seen this happen with SQ-D but if this is the case you can't reset.

5-Also check your cotacts on the contactor and be sure all 3 phases are closeing ar making contact and are not burned there quite easly accesed.

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