480 v 3 phase blower motor

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electricalist

electricalist

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dallas tx
We recently looked at some motors and there seems to be something going on with them. Some things I shouldnt say til I know more about the sollution.
There are 10 all 20 hp name plate says 12 amp when running. I should have took a pic of the n/p. 2 of them are tripping the starter
11276ddc143971b08022d7b4e5f9aea5.jpg
the star up is about 90 amps but as fast as a blink its down to 12/13 amps. We have checked connections . There is #10 awg thhn or thwn .feeding them. Any lb or j box that is in the run we have opened and to the touch wire are not hot. Mainly at the motor and the starter. Any suggestions
 
Did you
meg the motor
check running amps and start up amps
look for mechanical issues - bad bearing or belt

Often an electrical issue is from a mechanical failure
 
did you correct for temperture in panel

did you correct for temperture in panel

Your panel is almost 100 degrees with the door open, overloads are rated at ambient temp as per manufacture. They need to be raised as per manufacture if panel is higher
 
Yes sir I think you are correct. I couldnt get my phone in a position to take a pic of the n/p. By the math it is more likely to be a 10 hp
 
just the cowboy said:
Your panel is almost 100 degrees with the door open, overloads are rated at ambient temp as per manufacture. They need to be raised as per manufacture if panel is higher
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The temp was about 93. Im lisrening. I try not to point tge blame at other peoples equipment. So are you suggesting I find out the temp rating of the overall cabinet or the starter
 
electricalist said:
We recently looked at some motors and there seems to be something going on with them. Some things I shouldnt say til I know more about the sollution.
There are 10 all 20 hp name plate says 12 amp when running. I should have took a pic of the n/p. 2 of them are tripping the starter
11276ddc143971b08022d7b4e5f9aea5.jpg
the star up is about 90 amps but as fast as a blink its down to 12/13 amps. We have checked connections . There is #10 awg thhn or thwn .feeding them. Any lb or j box that is in the run we have opened and to the touch wire are not hot. Mainly at the motor and the starter. Any suggestions
Click to expand...

Is this a problem that recently started happening or is this since new? Looking for what has changed.

What exactly is tripping? overloads? circuit breaker?
When are they tripping? On startup? After running for a while?

What kind of starters are you using? MCC with Listed combination mag-only CB? TM CBs with contactors and overloads? mechanical overloads? Electronic overloads.

Answers to these will help with t-shoot direction

ice
 
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Those appear to be AB 140M motor circuit protectors, if so those are rated for 60C operation, about 140F without de-rating. But if your temperature is 93F with the door open, it's likely a LOT hotter inside of the box with the door closed.

Do they trip right away or after a while?

One thing about those devices is that they will trip early if there is a current imbalance, it's a way to help protect the motor. So on the ones that are tripping, record the measured current on each phase, don't assume that if you check one they are all the same.
 
just the cowboy said:
I just looked in a sq d starter and it said to use 125% of rating when starter enclosure is in 40C (104 f) . Also motors that are in hot or cold areas need to be derated, a cold motor is not protedted or hot motor is overprotected.


Nice motor overload info from AB http://literature.rockwellautomation.com/idc/groups/literature/documents/wp/icg-wp001_-en-p.pdf
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I actually bought the thermometer cause I wanted to see after the door is closed. . These are dryer motors at a car wash. I believe the starter s are ATL there is a philips type adjustment screw on the left of the starter.
 
just the cowboy said:
I just looked in a sq d starter and it said to use 125% of rating when starter enclosure is in 40C (104 f) . Also motors that are in hot or cold areas need to be derated, a cold motor is not protedted or hot motor is overprotected.


Nice motor overload info from AB http://literature.rockwellautomation.com/idc/groups/literature/documents/wp/icg-wp001_-en-p.pdf
Click to expand...
Thanks for the link ive been reading it I even sent it to a co worker. As for these motors I think its in my best interest to not concern myself any more. I found out there have been multiple hands on the motor terminations. Wiring was ran by electrician , motors supplied and installed by another and the cabinet with all the starters they call the mcc , as I read up on them its more of a cabinet that was built for starters. No specific. I can see that if any of the 3(mcc wire to motor, motor) components had a problem and got fixed it could have resulted in problems with the others.
Im not good at chasing ghost
 
The best thing to do is install a recording ammeter and see what is really happening with current. Any other is just a guess. If one is not available, see if they want you to rent one or borrow one from a POCO. An option is to use a Fluke or similar with a min/max setting and reset it after starting to see what the max running is. If it never gets above trip rating but trips anyway, you have overload protective device problems.
 
the star up is about 90 amps but as fast as a blink its down to 12/13 amps.
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My guess is they are 10 hp and not 20 hp motors, you said the nameplate says 12 amps - pretty popular nameplate rating for 10 hp.

if they are drawing 12/13 amps you are right on the protection limit and is really not too surprising you are tripping some of them. Don't know anything about the design of your blowers but if you can restrict flow just a little on the ones that are pulling too much you can probably bring that current down.

High ambient temp doesn't help any but you are still pulling too much if seeing 13 amps on a 12 amp rated motor.
 
Well for one, 93 degrees is warm but not too bad. Those starters should be able to handle that. Overload trips are slow usually, so if you get a fast trip you might
have shorts in wiring or windings. Or I have seen about 3 times at my job...contactors where 1 or more legs fuse. Or contacts develop some resistance on a leg.
You can pick those up with a clamp or kill the power and look for continuity across the contactor when it is not energized. You can kill the power, push in the contactor
manually and read across to catch bad contacts. And make sure the overloads are set right and no one miss wired a motor for the wrong voltage. Just because a motor
says it runs 20 amps doesn't mean it will in practice. It depends on the load on the motor. If you will be working on this kind of stuff then a clamp that will catch peaks is
very useful tool.
 
kwired said:
My guess is they are 10 hp and not 20 hp motors, you said the nameplate says 12 amps - pretty popular nameplate rating for 10 hp.
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I agree. In post#2, I mentioned that the current was not right for 20hp and the OP responded in post #5 that it was probably 10hp. The 90A starting current at 7.5 tomes FLC would accord with that.

kwired said:
if they are drawing 12/13 amps you are right on the protection limit and is really not too surprising you are tripping some of them. Don't know anything about the design of your blowers but if you can restrict flow just a little on the ones that are pulling too much you can probably bring that current down.

High ambient temp doesn't help any but you are still pulling too much if seeing 13 amps on a 12 amp rated motor.
Click to expand...

And I agree with all of that too.
There is another effect of high ambient if the fans are blowing ambient air.

The higher the air temperature, the less dense the air and the lower the loading on the fans.
We have a couple of fairly big fan drives (2,200kW) installed in a cement works. On restart after an outage, I've known them to sit in current limit rather than reach rated speed.
 
ActionDave said:
I find this to be true as many times as not.

The motor or overloads get blamed before any other part of the system gets checked.
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Yep. Easier to blame the electrics.
I've had a few real gems over the years.
Recently, it was mechanical vibration. Our drive so we had to investigate.
Nothing to do with the drive but you have to go through the motions.
About 20 years out of warranty but you still feel like you are having to defend your corner.
 
Were going back to this location today. These motors have ran without any problems for 2 days during buisness hrs. .there is a factory fan in the mcc. Filters for incoming and outgoing air were solid with dust and a box blocking air in. There was a disconnect, non fused that has failed at terminations in line and load side. Another disconnect was headed in the same direction. We have new disconnects and now I can read up on the exact specs to determin why they failed. They apear to have gotten hot at terminations. If they are listed and approved for this application. Can I look at either the motor the motor connections or something from the motor to the disconnect as the original corruption? Thanx
 
electricalist said:
Were going back to this location today. These motors have ran without any problems for 2 days during buisness hrs. .there is a factory fan in the mcc. Filters for incoming and outgoing air were solid with dust and a box blocking air in. There was a disconnect, non fused that has failed at terminations in line and load side. Another disconnect was headed in the same direction. We have new disconnects and now I can read up on the exact specs to determin why they failed. They apear to have gotten hot at terminations. If they are listed and approved for this application. Can I look at either the motor the motor connections or something from the motor to the disconnect as the original corruption? Thanx
Click to expand...
If they failed at terminations, I would suspect connection was not properly tightened to be the primary reason for that failure.
 
I agree except . I am 100% sure all disconncts were checked for loose wiring by 3 electricians. These motors were problematic before the disconnect failures. ..first thing done was check all connection and terminations. Would it benefit us to heat test these points with infrared
 
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