# Sticking starter



## micromind (Aug 11, 2007)

The contacts of most starters, even good ones, will weld if there's a fault of some sort downstream. 

I've had (rarely) contacts of IEC starters weld with no faults and the motor was a short distance from the starter and the system was very low impedance. 

First thing I'd do is megger the motor and look at winding resistance. If that is ok and it's a big motor, a surge test would be a good idea too.


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## tates1882 (Sep 3, 2010)

Gpatrick said:


> I have a control panel that keeps welding contactors shut. It only happens when the motor is plugged in at the bottom of the overload. It's a 3 phase system. I swapped out the starter and overload and it did the same thing. My money is on a bad motor but has anyone ever seen this issue?


Plenty of times. Usually from the ol being set too high. Why'd you replace the starter without megging or at least ringing out the motor? 




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## frenchelectrican (Mar 15, 2007)

Gpatrick said:


> I have a control panel that keeps welding contactors shut. It only happens when the motor is plugged in at the bottom of the overload. It's a 3 phase system. I swapped out the starter and overload and it did the same thing. My money is on a bad motor but has anyone ever seen this issue?


I have see it pretty often espcally with undersized starter or get damaged with high intera loads and from time to time when someone use the reversing starter they switch from one direction to other direction too quick and end up plugging hard which it will weld concants.

If the overload heater or setting is too high then a good chance it will weld shut too.

I would megger the motor to make sure it is ok otherwise it will keep contuinde the issue what you have now.


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## bill39 (Sep 4, 2009)

Gpatrick said:


> I have a control panel that keeps welding contactors shut. It only happens when the motor is plugged in at the bottom of the overload. It's a 3 phase system. I swapped out the starter and overload and it did the same thing. My money is on a bad motor but has anyone ever seen this issue?


Just curious, are these NEMA or IEC starters? I believe everyone will agree that NEMA are more rugged.


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## micromind (Aug 11, 2007)

WAY more rugged......


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## telsa (May 22, 2015)

Rugged or Shagged ?


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## frenchelectrican (Mar 15, 2007)

telsa said:


> Rugged or Shagged ?


LOL.,,

but basically the NEMA starters are like diesel engine block compared to IEC starters like gas engine block.,,

so that is a super rough grist.,, :whistling2:


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## Gpatrick (Sep 2, 2017)

I was pressed for time so pretty much was told to throw parts at it. I also need to invest in a meggar as well. I appreciate the quick and helpful responses guys.


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## joebanana (Dec 21, 2010)

Is the starter the right size for the motor?


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## MechanicalDVR (Dec 29, 2007)

Welcome aboard @Gpatrick!

I see there are plenty of questions here for you about the starter that's bad.


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## bill39 (Sep 4, 2009)

joebanana said:


> Is the starter the right size for the motor?


If the starter is indeed being used for plugging, then it should be up sized no matter whether is is IEC or NEMA. Just my opinion.


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## micromind (Aug 11, 2007)

bill39 said:


> If the starter is indeed being used for plugging, then it should be up sized no matter whether is is IEC or NEMA. Just my opinion.


Most, if not all, manufacturers have tables listing jogging and plugging ratings for their starters. 

I don't know if these are NEMA ratings or manufacturer ones but they are less than full-voltage starting.

For example, the Allen Bradley book lists a NEMA size 1 as 10 HP @ 480 volts for normal starting. For jogging or plugging, it's 5 HP. A size 3 is 50 HP vs. 30 HP. 

I don't know about IEC ratings, it wouldn't surprise me if the first time a motor was plugged using an IEC contractor, it'd just blow up.......lol.


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## frenchelectrican (Mar 15, 2007)

micromind said:


> Most, if not all, manufacturers have tables listing jogging and plugging ratings for their starters.
> 
> I don't know if these are NEMA ratings or manufacturer ones but they are less than full-voltage starting.
> 
> ...


Microminded.,,

I have dealt alot of IEC starter and if it was used for plugging my quick rules is upsize at least twice some case 3X what it normally used on simple DOL system is. 

And Ya I have see those IEC blow up with hard plugging.,, no fun when they blow up.,, ( especially on 400 volts and above system )


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## JRaef (Mar 23, 2009)

If you are confident that the starter is correctly sized and applied, that the motor circuit is good, etc., another very common cause of contact welding is that the contactor is "chattering". That means it is rapidly turning on and off, sometimes so fast that you don't notice it unless you have the door open and see a blue flash. That is usually the result of a problem in the control circuit, either a bad component or an under sized control transformer. Start eliminating the possibilities and report back.


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## frenchelectrican (Mar 15, 2007)

JRaef said:


> If you are confident that the starter is correctly sized and applied, that the motor circuit is good, etc., another very common cause of contact welding is that the contactor is "chattering". That means it is rapidly turning on and off, sometimes so fast that you don't notice it unless you have the door open and see a blue flash. That is usually the result of a problem in the control circuit, either a bad component or an under sized control transformer. Start eliminating the possibilities and report back.


Thanks for bringing it up and remind that part and yuh .,, that is one of most common curpit too.


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## John Valdes (May 17, 2007)

How much current is the motor pulling at load?


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## Southeast Power (Jan 18, 2009)

I had that problem with a small IEC starter with a brake motor years ago.
I ended up putting the CORRECT fuses in it and it continued to blow them until we addressed the brake problem.
Its very possible that the controls are doing their job and you have a motor fault problem.
Also, very good observation from Micromind about the correct sizing and Jraef about the CT being weak.


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## goodtimesgladly (Sep 12, 2017)

I have only seen similar problems on IEC products especially imported brands. I only use NEMA and name brands such as Allen Bradley. I will choose a used Allen Bradley before I would use a brand new FUJI. I have actually seen FUJI overloads burn up and even catch fire and do not even trip. This happened twice to me and I now only use Allen Bradley.
You get what you pay for. By the way who did the engineering? What type, size of fusing or CB's? Management should be concerned about safety and not just throwing parts at it as a guy could get burned or worse. If you work around electricity a lot like every day then finding the problem is elementary. I always start with the motor and work back and not the other way around otherwise you will just throw parts at it as you say.


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## paulengr (Oct 8, 2017)

The problem with IEC is most people don't understand it and end up under sizing everything. IEC has different use categories like AC-3 which is what the catalog number is. To get equivalent to NEMA you need to size it for AC-4 and 2 million cycles. iEC defaults in most catalogs to AC-3 and 1 million cycles. If you check the curves and make it NEMA-like which as stated usually means 1 or 2 sizes bigger, it does just fine. And it is still much smaller and has a lot more options for panel builders. But that's in the IEC standard, not the catalog, so many people get burned in buying the wrong IEC contactor by not knowing what the specs mean because NEMA has a fixed duty cycle. With IEC contactor specs you can actually exceed NEMA once you know this.

Contact welding is caused by too much current for too long for the size contact. It can still happen sometimes IEC has "type 2" starter designs which means that unlike NEMA the starter system including a current limiting short circuit protection (current limiting fuse or MCP) are "no damage"... you can clear the fault and go right back to work. IEC type 1 starters allow the starter to be destroyed as long as it interrupts the fault which means the contactor can be melted slag or contacts welded shut because it must be tested before being put back into service. NEMA doesn't have this designation but since it has no " light duty" ratings such as for capacitors, lighting or resistive heating, or bypass contactors, the starter usually survives. But again...IEC has the option to allow contactor damage or not.

So what I find is that its not usually a brand thing (LSIS, FUJI, ABB, Sprecher-Schutt) or a NEMA/IEC thing with industrial control panels but more often a type 1 design with AC-1 contactors which might be barely OK turning a resistance heater on but is totally inadequate for an industrial motor application but gets used anyway because hey its 45 mm wide unlike the NEMA one that is 90 mm wide. But the properly sized IEC contactor might be 90 mm wide too or maybe 60 mm and now that I've been asked to fix it, I have to come up with another 45 mm of label space in an already overstuffed box. I stick with IEC because it is more compact and flexible for retrofits where I'm usually already limited on space. iEC contactors also often come with economizers too so panel heating and power draw is less, and they are often available with 24 VDC coils, something unheard of in NEMA where you are forced to add isolation relays.

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