# AB motor starter



## ponyboy (Nov 18, 2012)

Bump


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## erics37 (May 7, 2009)

Give it the ol' Fonz.


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## ponyboy (Nov 18, 2012)

erics37 said:


> Give it the ol' Fonz.


Naturally that was my first method. There's 80 of these buggers in the cabinet and it happens randomly to random starters


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## erics37 (May 7, 2009)

ponyboy said:


> Naturally that was my first method. There's 80 of these buggers in the cabinet and it happens randomly to random starters


Not too familiar with AB stuff. Is it an MMS? I've found that those can be...... weird...... when it comes to operating/resetting them.

Are yours tripping for legitimate reasons like overload? Maybe you're right; they probably have to cool off a bit or something in order to reset them.


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## MTW (Aug 28, 2013)

Black, white, red, yellow, blue.


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## nolabama (Oct 3, 2007)

I am thinking it's thermal and takes time to cool down. Check with infrared thermometer if they don't latch . Chances are it's doing its job.

http://www.ab.com/en/epub/catalogs/12768/229240/229254/229469/3100802/Specifications.html


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## micromind (Aug 11, 2007)

Those starters very likely have a time delay for O/L reset. Here's why.....

If a motor is overloaded enough that it trips the starter, then the motor is very close to its maximum insulation temperature. If the starter allowed an instant O/L reset, the motor would still be hot. If there's a time delay, the motor will cool......well, somewhat anyway.....


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## ponyboy (Nov 18, 2012)

micromind said:


> Those starters very likely have a time delay for O/L reset. Here's why..... If a motor is overloaded enough that it trips the starter, then the motor is very close to its maximum insulation temperature. If the starter allowed an instant O/L reset, the motor would still be hot. If there's a time delay, the motor will cool......well, somewhat anyway.....


Thanks for the info. I haven't given this issue my full attention yet but I can't imagine why any of these motors would be running overloaded. They are for a conveyor that runs off and on for 10 hours a day and when they start tripping there is no obvious pattern in what's been reported to me.

My thought is maybe they are grouped too tight in the cabinet. There are three rows of 25~ starters mounted on a buss rail and they are virtually touching each other from left to right. I also wonder if a thermal scan might turn up something even though physically nothing feels hot to touch


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## ponyboy (Nov 18, 2012)

nolabama said:


> I am thinking it's thermal and takes time to cool down. Check with infrared thermometer if they don't latch . Chances are it's doing its job. http://www.ab.com/en/epub/catalogs/12768/229240/229254/229469/3100802/Specifications.html


 I notice under the general-life span section there is a max rating of 25 operations/h. Do you think this is literally saying this starter shouldn't be switched more than 25 times per hour?


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## Cow (Jan 16, 2008)

ponyboy said:


> Thanks for the info. I haven't given this issue my full attention yet but I can't imagine why any of these motors would be running overloaded. They are for a conveyor that runs off and on for 10 hours a day and when they start tripping there is no obvious pattern in what's been reported to me.
> 
> My thought is maybe they are grouped too tight in the cabinet. There are three rows of 25~ starters mounted on a buss rail and they are virtually touching each other from left to right. I also wonder if a thermal scan might turn up something even though physically nothing feels hot to touch


They are made to be next to each other, AB sells feeder buss to link a bunch of them together side by side. I've used quite a few of these manual motor protectors and haven't had any issues. I've never had a problem resetting them after they've tripped but usually when I show up on site it's been a while since it's happened. 

I would start by amping and megging the motors with issues. Have you verified motor nameplate current matches the dial setting?

Maybe it'd be worth it to put some colored stickers on the ones you're having trouble with to see if it's the same ones tripping over and over again.


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## Chrisibew440 (Sep 13, 2013)

ponyboy said:


> Thanks for the info. I haven't given this issue my full attention yet but I can't imagine why any of these motors would be running overloaded. They are for a conveyor that runs off and on for 10 hours a day and when they start tripping there is no obvious pattern in what's been reported to me.
> 
> My thought is maybe they are grouped too tight in the cabinet. There are three rows of 25~ starters mounted on a buss rail and they are virtually touching each other from left to right. I also wonder if a thermal scan might turn up something even though physically nothing feels hot to touch


 

thats what im thinking, to much heat.... replace them all with telemecanique or put in some axiual? fans. one on the top right for negative preasure and one on the bottom left for pausitive.


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## Chrisibew440 (Sep 13, 2013)

the reason i say telemecanique is because ive built mcc's with them side by side anywhere from 80 to 300 starters in a cabinet and never had an issue. yet ive replaced AB's stuff for this same problem your having.


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## nolabama (Oct 3, 2007)

I would buy A - B before Telemecanique any day of the week. Thermal scan is in order.


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## JRaef (Mar 23, 2009)

ALL thermal overload protective devices, as those are, are REQUIRED to take time to reset. The time is carefully chosen by virtue of the bi-metal strip materials in an attempt to approximate the thermal cool-down constant of the motor, meaning the rate at which the motor will cool down based on standard design conditions. 

The difference between A-B and Tele in that respect would be that Tele, being a French company, bases their design on IEC motors, which have NO service factor and require fast tripping OLs set at class 10 or lower. That means the motors tripped a lot sooner, therefore they are not as hot and cool off faster. A-B on the other hand, being a North American company, bases the reset time on NEMA motor designs, which allow for a 1.15 service factor *and *a class 20 trip. So yes, the AB versions will take longer to reset, but that's because it held in a lot longer and the motor got a lot hotter. The Tele versions will trip more often if using a NEMA motor, or to look at it the other way, the Tele will not allow you to take advantage of the added thermal capacity of a NEMA motor.

The AB units are OK with "zero stacking" meaning mounting right next to each other. But ALL bi-metal OL devices are susceptible to high ambient heat inside the box. The trip times are based on the device being in a 25C environment, and have automatic compensation to adjust themselves for up to 40C (104F). But after that, all bets are off. Each unit gives off about 9 watts of heat, so if you have dozens of them in a box, it all adds up. So if you are POSITIVE that the motors are not really being overloaded, then it's likely a cumulative heat problem in your enclosure.


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## don_resqcapt19 (Jul 18, 2010)

JRaef said:


> ... The time is carefully chosen by virtue of the bi-metal strip materials in an attempt to approximate the thermal cool-down constant of the motor, meaning the rate at which the motor will cool down based on standard design conditions. ...


How do they make that work given the huge difference in mass between the bi-metal strip and the motor windings?

It has been my experience that overload relays with the bi-metal strips can be reset almost instantly. The melting alloy types can't be.


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## Big John (May 23, 2010)

Somewhere I have video of a 50HP motor with smoke just rolling out of it because the operators kept hitting the damn reset every couple minutes when it went out on OL. There is a delay in those bimetallics, but it doesn't come anywhere near to accurately representing the thermal mass of the motor. 

Those combination AB starters are bimetallic, so I agree that's also very likely your problem.


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## ponyboy (Nov 18, 2012)

I confirmed my suspicion this morning that this wasn't an overload issue but a thermal issue contained to the problematic starters. I hit the cabinet with a thermal imager this morning and immediately found the impaired connections. It's never been my habit to check the hundreds of panel shop terminations for proper torque but it would've saved us a headache for sure. It took me over an hour to check the rest of the feeder terminals.


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## JRaef (Mar 23, 2009)

don_resqcapt19 said:


> How do they make that work given the huge difference in mass between the bi-metal strip and the motor windings?
> 
> It has been my experience that overload relays with the bi-metal strips can be reset almost instantly. The melting alloy types can't be.





Big John said:


> Somewhere I have video of a 50HP motor with smoke just rolling out of it because the operators kept hitting the damn reset every couple minutes when it went out on OL. There is a delay in those bimetallics, but it doesn't come anywhere near to accurately representing the thermal mass of the motor.
> 
> Those combination AB starters are bimetallic, so I agree that's also very likely your problem.


The bi-metal design is SUPPOSED to match the thermal time constant of a typical motor. But not all OL relays are created equal. Cheap ones are designed to be cheap, good ones are designed to be good. When I worked as a Product Manager for a company developing a soft starters with an integral bypass that needed a stand-alone OL relay, we tested every one of the major manufacturers to look at reliability, repeatability and sensitivity. I was amazed at how much variation there was. A LOT of the IEC bi-metal OL relays tripped WAY sooner than they needed to. Class 10 says 10 seconds at 600% current, some were as short as 3 seconds but technically that satisfies the requirement, which only says no MORE than 10 seconds. When that is the case it's a nuisance but it would in theory be able to be reset faster. The design spec also calls for trip and reset just once. So after the second trip, all bets are off. Remember, most of the time a motor runs UNDER it's FLA rating and if the OL trips, it's usually because it really is overloaded. But nothing can be made idiot proof, and constantly resetting while doing nothing to fix the overloading problem is right on Webster's page defining "idiot". 

After that eye opening experience though, I ONLY use solid state overload relays now unless there is no other choice. No thermal issues to deal with.


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## hardworkingstiff (Jan 22, 2007)

Sounds like someone should give you an atta-boy. So here's one from me, :thumbsup:

Please don't take this as sarcasm or condescension, it's sincere.


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## nolabama (Oct 3, 2007)

ponyboy said:


> I confirmed my suspicion this morning that this wasn't an overload issue but a thermal issue contained to the problematic starters. I hit the cabinet with a thermal imager this morning and immediately found the impaired connections. It's never been my habit to check the hundreds of panel shop terminations for proper torque but it would've saved us a headache for sure. It took me over an hour to check the rest of the feeder terminals.


lol. Crummy shop terminations. I had fits with that once. DC and it got real hot.


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## just the cowboy (Sep 4, 2013)

hardworkingstiff said:


> Sounds like someone should give you an atta-boy. So here's one from me, :thumbsup:
> 
> Please don't take this as sarcasm or condescension, it's sincere.


Just remember one "Oh S**t" when working cancels out 100 atta-boys:whistling2:


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## don_resqcapt19 (Jul 18, 2010)

JRaef said:


> The bi-metal design is SUPPOSED to match the thermal time constant of a typical motor. ....


I have never heard that before, and I just don't understand how that is even possible, unless there is some electronic time delay circuit in the overload relay. 

The mass of the motor will be 100s to 1000s of times greater than the mass of the bi-metal heater.


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## JRaef (Mar 23, 2009)

don_resqcapt19 said:


> I have never heard that before, and I just don't understand how that is even possible, unless there is some electronic time delay circuit in the overload relay.
> 
> The mass of the motor will be 100s to 1000s of times greater than the mass of the bi-metal heater.


You are equating the cooling rates and no, they would not be the same. That's not what I meant. It's the RESET time of the bi-metal strip that is selected to try to approximate the cooling time constant of the motor. So the time it takes for the bi-metal strip to straighten out again must allow the hottest spot in the motor to dissipate enough of its heat, by conduction and radiation, to where you have gained sufficient thermal capacity to successfully restart. Once. 

In good Solid State overloads, the thermal run up at acceleration is measured and recorded in memory so that the reset time is more accurately determined. Can't do that with a bi-metal device, so it's approximate. There is a lengthy process involved in that bi-metal strip design. IIRC, the motor thermal status must have dropped to 75% of capacity, assuming it takes roughly 25% of the thermal capacity of a motor to accelerate a load that is 75% of rated capacity.


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## hardworkingstiff (Jan 22, 2007)

just the cowboy said:


> Just remember one "Oh S**t" when working cancels out 100 atta-boys:whistling2:


Wow, inflation.

When I 1st heard that (mid to late '70s) it was "It takes 10 atta-boys to make up for one oh chit". Then it went to 20 in the 80's 90's, now it's up to 100,  :laughing:


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## don_resqcapt19 (Jul 18, 2010)

JRaef said:


> You are equating the cooling rates and no, they would not be the same. That's not what I meant. It's the RESET time of the bi-metal strip that is selected to try to approximate the cooling time constant of the motor. So the time it takes for the bi-metal strip to straighten out again must allow the hottest spot in the motor to dissipate enough of its heat, by conduction and radiation, to where you have gained sufficient thermal capacity to successfully restart. Once.
> ...


I guess I just have never seen one that works correctly...all of them I have worked with you could reset in a matter of seconds after they have tripped. I can't imagine the the motor has cooled enough in that time. Even the eutectic types that I have worked with could be reset in about a minute.


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## IP-EI (Apr 7, 2014)

don_resqcapt19 said:


> I guess I just have never seen one that works correctly...all of them I have worked with you could reset in a matter of seconds after they have tripped. I can't imagine the the motor has cooled enough in that time. Even the eutectic types that I have worked with could be reset in about a minute.


I work maintenance, and resetting overloads is one of my most common calls. I deal with primarily the bi-metal types, and if I'm nearby when one trips I usually have to stand there for 2-4 minutes waiting for OLs to cool enough to reset. That few minutes seems really long when the equipment is locked up (like a chain hung in a screw conveyor) and I have to repeatedly reset the OLs and reverse rotation about 20 times to get the chain out.....


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## erics37 (May 7, 2009)

hardworkingstiff said:


> Wow, inflation.
> 
> When I 1st heard that (mid to late '70s) it was "It takes 10 atta-boys to make up for one oh chit". Then it went to 20 in the 80's 90's, now it's up to 100,  :laughing:


It's because of free trade agreements; now we have to compete with cheap foreign labor.


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