Contactor Not Automatically Energizing

If the contactor is humming, it is getting current.

Possibly resistance in the switch or another part in the circuit is causing insufficient current to reach the contactor. It may be low voltage in the circuit energizing the contactor. Or there could be friction in the contactor.

Measure the voltage at the contactor when it is energized and compare with the voltage supply to the circuit. If it is less, find the point in the circuit where the drop is occurring.

you say it is getting current, but how did it get out of date?

We all seem to be as hungry for questions as buzzards are hungry for a dead rabbit on the shoulder of a highway.

Here we are again, playing 20 questions with OP that is probably about to take a hike, if not already seen disappearing into the distance down the road that leads to (and away from) CR4.

I think you mean hungry for answers to follow-up questions. I totally understand that there doesn't seem to be that much traffic here. Aside from the "Start a Discussion"s from members, 5 or 6 "Ask a Question"s a day on average does seems pitiful.

A thought: If the incoming questions increased by a factor of say 5, would an equivalent percentage reveal OPs that never came back to their own post to answer followup questions that are absolutely necessary to identify the problem? That's the one that gets me the most.

I come here for 3 reasons. 1) To learn and absorb, 2) To be entertained, and 3) To try and help if it falls within my knowledge and experience.

For the most part, I enjoy my time here.

Yes, same here, and thanks for helping me in the past, by the way.

Right now, you and I are mostly hearing the sound of crickets chirping on threads like this, but the quiet is the lack of informational followup by the OP.

I think he said the motor was humming, does this indicate a star delta starter?

It sounds as though the contacter coil is open or not receiving its supply voltage.

Was it working before? or is this a new installation? Does the contactor stay closed when you push it in? Is the contactor closing just not making good contact? How do the contact point surfaces look, are they clean or burnt looking?

If the power supply for the coil has not changed, as per its specifications,

It is possible the contacts on the selector switch has developed some resistance, thereby reducing the voltage that otherwise meant for the contactor coil..

A quick way to test is by putting a short jumper wire across the selector switch contacts taking note if the contactor will close by itself, without giving it any push..

Otherwise it is also possible the coil characteristics of the contactor has changed, ie., developed higher coil resistance, that now is looking for a much higher amount of current to actuate? Typical thing to happen on old devices and therefore need to be replaced...

Among the possibilities:

• Wrong voltage, either supply or coil
• Mechanical obstruction to be removed
• Needs lubricating
• Series resistance to be removed
• Etc.

Keep trying.

I just checked for wrong voltage and the voltage at the A2 (coil) is lower than expected

SO what next can i do

You have two options.

First, find out where and why your voltage is lower than expected and correct the voltage drop. This solution is nothing but a band aid fix. This failure will happen again.

Second, replace the contactor with a suitable contactor having a coil with a pull in voltage that is lower than your discovered low voltage.

Actually, the first question, yet to be answered is details about the set-up specs.

Second question is how low is the voltage below specs?

The third is where is the loose connection? Improper wiring?

Fourth is where is my replacement contactor with the lower pull in requirement?

• Needs lubricating --> to make it more slack? Are you serious PWslack?

Some parts could have corroded, and might need removal, cleaning, and lubrication prior to placing back in the MCC.

If I had a contractor that was not a self-starter, I too would want to push him over a cliff in a wheel chair.

I would push him right past the donuts and coffee.

Are you connected to a PLC? Maybe the run confirm bit (relay) is not connected back to the contactor, and that may result in the PLC removing the start command from the motor on the next scan.

Wild guess - too little data presented - last time I saw this happen here, someone had ordered the contactor with 120 volt coil, and per my schematics, which the contactor purchaser didn't follow, we ran 24 volt to the contactor coil. It will latch in at too low a voltage but not pull in.

The rating of the CPT control Power transformer should be checked, if you have one. Too small a transformer to handle the coil inrush is a now & then problem, if you are building something from scratch. Though a 50VA transformer, about the smallest you might find should pick up that contactor.

The specs say 85% voltage, so 187V should pick it up, reliably.

OH, so there is the problem. Those three letters on there. Not only that, this thing says NO on it twice. That should be a clue. You need a "YES" contactor. LOL

This "thing that says NO on it", is a good hint.... it is an auxiliary contact that can be used as a latching mechanism for the coil.... When closed it connects the coil directly to its power supply... Manually pushing the contactor relay will make that a "yes" making his motor run!

JS strikes again!

"yAy!", an actual image! ... now we have taken the 1st "baby-step".

So, you stated in #11 that you checked, and, "the voltage at the A2 (coil) is lower than expected".

Well ; if the image you've posted is, in fact, correct then,

with your meter across A1 & A2 (and your "selector switch" in the "On" position) you should read 220-230v IF you are using it in 50Hz region, and/or 230-240v IF you are using it in 60Hz region.

This is, of course, assuming that your image is 100% correct... and NOT just a "generic" image (the contactor you posted is available with coils from 12v up to 600v).

Ergo (NOW), the question remains (as asked in Post #13)

"how low is the voltage below specification?"

[and, what OTHER information might you be able to add-into the equation here, at this stage...? Motor being driven / current draw at start-up, FLA...? What type of "selector switch" is involved, to which you made reference?]

Have you considered providing a depiction of the circuit involved...(see links in prior post)...?

^{this is exactly what am saying the voltage across A1 and A2 is 190v and not 220-230}

^{Is its about 30v lower}

^{So what can i do to correct this}

Find the wiring diagram. Test the nodes going back to your source to see where the voltage dropped from 220 VAC to 190 VAC. This should tell you what to fix. It will depend on what is failing how one fixes it. My WAG is that you have a poor connection somewhere.

If this baffles you, hire an electrician. They can safely perform this work safely.

Have you read my suggestion in post #4.... your selector switch may be the one causing the voltage drop?

That may be a quick way to find out if you really need to replace any component..

specially if the 220 volt supply is up to par?

First, determine why the voltage is low. Measure every step where there might be a voltage reduction from full. Eliminate all improper resistances. Tighten all connections. Etc.

After 22 posts, "finally", we have some numbers...(!)

So, now, as both redfred and Tornado have suggested, you need to plug-in the test leads, turn your meter "On", and do some troubleshooting.

We can't tell you EXACTLY where to place the test-lead-probes without having some semblance of an idea as to WHAT the EXACT situation is... as previously asked;

Having asked THRICE now, in (my) Post #8 above ("an actual Circuit Diagram"), and repeated in (my) Post #17 (bottom line), and RE-repeated in (my) Post #21;

? Got a sketch (a schematic , a diagram) ?

IF this is "way-over-your-head", to produce at least a rudimentary "map" of what you have (especially, having been pointed to some nice, "standard" examples)... AND, if you are unable to answer those OTHER questions, asked above {again, see #21)...

... then, we shall all have to keep "shotgunning-it".

Try the blue wire... (and always keep one hand behind your back).

Trust me, this cat has no intrinsic ability to troubleshoot, and really should not be allowed near power tools, equipment, or industrial control cabinets.

He only has 8 lives left.

"Aye" to that. When you had asked him (in #13), "How low?" (is the voltage), and I repeated that question in #17, and he replied with:

"this is exactly what am saying the voltage across A1 and A2 is 190v and not 220-230

Is its about 30v lower _^(sic)

So what can i do to correct this"

... it was all I could do to NOT respond with "You need to get a boosting transformer to bring your voltage back up to what it should be. Your 190v measurement is about 15% low from what it should be. Read below the image on the 1st page, and the 1st sentence on page 2... you'll see that something like THIS should do the job well."

I hope-&-pray that I never-Never-NEVER become SO cynical as to preclude the "Golden Rule" from being able to keep me in-check...

Hey, that's the same place Wiley E. Coyote gets his road-runner trap parts and kits.

God bless you, senor.

...... ^{much of what I learned {what NOT to try} CAME from that Saturday morning "Bud"}... ((Linked ⇓ ))

Please do not suggest the boost transformer. It is not a good idea. Troubleshooting the rest of the elements of the system is much more appropriate. If there is some power limiting element, the boosting transformer will do no good.

With ALL due respect . . . please read posts THOROUGHLY and IN-FULL-CONTEXT before responding in such "antidotal" fashion.

I was NOT suggesting that ... I believe that I made it poignantly clear that I could NOT bring myself to make such a suggestion, (in-doing-so) displaying the cynicism that frequently erupts when people [both OP's & responders] do NOT pay attention to what is being asked; especially when questions are asked r-e-p-e-a-t-e-d-l-y...

{read my other posts here BEFORE re-reading this one, to which you replied, and perhaps you will better "follow" what I am saying...}

Check the voltage step by step and locate where the voltage is dropping . It may be a poor contact may be carbonised/damaged contact .Clean it or replace the defective contact .Your problem will be solved. Get a good electrician who can fix it.

According to the specs

Rated Operational Current AC-3 (Ie): (220 / 230 / 240 V) 55 °C 9 A (380 / 400 V) 55 °C 9 A (415 V) 55 °C 9 A (440 V) 55 °C 9 A (500 V) 55 °C 9 A (690 V) 55 °C 7 A

190V is below the minimum rated voltage, so it is normal it will not work.

If you want an advice, use an auxiliary contactor, capable of providing those 9A. I would not add such a high load directly to a conventional wired system.

Actually, if you re-read ndt-tom's response, it was all he could do not to suggest a buck-boost transformer, tongue-in-cheek. Get the joke?

As you astutely pointed out, the only way to provide the needed power for pull-in is to provide the correct voltage, either by fixing the circuit, or adding a sub-contactor, a definite purpose contactor, as you referred to it, an auxiliary contactor.

It appears I miss read your question "the motor does not run as well, it will just hum" does not run as well?

So the contactor is humming?? the voltage across the coil is low, so read the voltage at your switch when on and when off it will indicate a faulty switch or supply to the switch then trace the wires back to the supply for a bad connection.

No, the contractor that installed the ABB contactor is humming (and singing and laughing) all the way to the bank.

So am I, but then again, I am just sitting here doing nothing, waiting for 45.3 MW to being dispatchable, so I can go about my normal routine.

It hums because it simply doesn't know the words.

<Boom-tish!>

mmmm

<tish tish boom>