# AB soft start



## gpop

I have a AB soft start with a smc dialog plus controller. breaker, primary contactor, soft start, bypass contactor. 

Motor was running fine the day before but failed to start the next day. Motor load is to big to start on the bypass for testing. 

Soft start closes the primary breaker when the start button is pressed then trips after 1-2 seconds on f15 fault. (motor does not turn)

F15 which is a line loss fault. There is a note in the manual where you can reset with out shutting the softstart down then try to restart and it should report what phase the problem is on. When we tried this it just went back to f15 so it may be seeing all phases as lost. 

Followed the manual and tested with a ohm meter for shorted gates or problems with the gate drivers. All readings are with in limits. Tested load side just because i was there and again no problem was detected. 

Suited up and checked line side voltage in the 1-2 seconds that the primary is closed and voltages are with in limits. 

95% certain that the control module is bad but i do not have a spare to test it. 

AB obsoleted the controller back in 2015 so its going to be a hassle getting a new one which means i need to be sure that i haven't missed anything.

Any one have a history with this style of softstart.


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## MDShunk

I don't know, but I'm curious how many HP this motor is?


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## Cow

How old is the softstart? 



How many starts per hour/day?


What's it running?


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## gpop

MDShunk said:


> I don't know, but I'm curious how many HP this motor is?



I can not remember of the top of my head. About 50-60hp.


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## MDShunk

My only advice is probably something you already know and/or have done. Check that motor and the associated conductors from the SS to the motor upside down and backwards before trying new parts in the SS bucket.


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## gpop

How old is the softstart? 

Last time i replaced the controller was about 13 years ago so its older than that.

How many starts per hour/day?

probably 2 or 3 times a day on average


What's it running?

High pressure water pump. Its the type that spins a large drum and a scraper blade on the inside scopes the water from inside surface of the drum. Takes about 20-30 seconds to come up to speed or it will smoke the belts


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## MDShunk

If you're sure the load is in good shape, you have a spare VFD of a suitable size that you can flop on a cart and temp in to rule in or out the SS as the point of failure? I hate playing swaptronics, but there's no fantastic way to test a SS that faults out so quickly.


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## gpop

MDShunk said:


> My only advice is probably something you already know and/or have done. Check that motor and the associated conductors from the SS to the motor upside down and backwards before trying new parts in the SS bucket.



Normally the controllers are good about explaining the problem but f15 is a little fluffy

Line Fault ②
(no phase indication)

F15 and
F29

• Missing supply phase (tested and passed)
• Motor not connected properly (tested and passed according to the meter, Have not visibly checked as no one has touch it)
• Shorted SCR (tested and passed according to ohm reading)


• Check for open line ( i.e., blown fuse) (tested and passed)
• Check for open load lead (all 3 legs ohm low to each other)
• Check for shorted SCR; replace if necessary (tested and passed)


Shorted SCR Test
1. Using an ohmmeter, measure the resistance between the line and
load terminals of each phase on the controller.
The resistance should be greater than 10,000 ohms.

Feedback Resistance
1. Measure resistance between pins 1 and 2.
Resistance should be 19,000 ohms, +/–5%.
2. Measure resistance between pins 7 and 8.
Resistance should be 19,000 ohms +/–5%.
Gate Lead Resistance
1. Measure resistance between pins 2 and 3.
Resistance should less than 100 ohms.
2. Measure resistance between pins 6 and 7.
Resistance should be less than 100 ohms.
Thermistor Resistance
1. Measure resistance between pins 4 and 5.
Resistance should be less than 150 ohms.
If the power module fails any of the above tests, replace it.


Only thing i haven't tried yet is to flash the memory back to factory and reprogram the unit.


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## gpop

MDShunk said:


> If you're sure the load is in good shape, you have a spare VFD of a suitable size that you can flop on a cart and temp in to rule in or out the SS as the point of failure? I hate playing swaptronics, but there's no fantastic way to test a SS that faults out so quickly.



hmmm i like the way you think. I have a modern SS thats a spare but it doesn't use bypass contractors and would not be a easy install but a vfd wouldn't be a heavy lift to test the line and load.


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## MDShunk

If you haven't already done it, don't rule out that the pump rotor isn't locked up to the drum and the motor draws LRA for too long and trips out the primary contactor. This a wye-delta or does it just have primary contactor out of tradition?


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## gpop

MDShunk said:


> If you haven't already done it, don't rule out that the pump rotor isn't locked up to the drum and the motor draws LRA for too long and trips out the primary contactor. This a wye-delta or does it just have primary contactor out of tradition?


SS wont even send voltage to the motor. As far as it is concerned its failed a test so it faults rather than trying to start. 

When you press start the (primary) isolation contractor closes supplying voltage to the SS. (the SS controls the contactor). After a second or two it decides that there is a problem and shuts down on F15.
Its almost like the internals in the control box does not see the voltage on the line side (none of the 3 phases). 
There are other alarms to indicate if you loose one phase or have a low or high voltage condition. There are also alarms to indicate load loss and a bunch of other problems.


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## Rora

Just for clarification, it's only giving F15 and not F29, although that's grouped in the same part of the manual, right? I'm inclined to believe the error at face value, i.e. it really thinks there is a problem on the line side. Curious what would happen if you disconnected the load whether it would even get to that point of self-test to indicate what it believes is a line fault, doubtful though.

Seems like one of those problems that indicates an unattractive resolution, so you try everything hoping it's something else. Pretty clear that you've done your due diligence and a replacement wouldn't be inappropriate. Swapping something else on hand would give an even greater degree of confidence if getting another one is really that difficult.


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## frenchelectrican

The last time I got hit with F15 and F23 at the same time.,

I did test the phase rotation pretty closely due sometime if phase shifted just enough to make the SS go bonkers and cry code F15 or F23.

and yes I did reboot the whole bloody thing back to factory setting and work it way out to correct setting.

but you mention a older model ., I dont recall excatally which model did have interal back up battery for memory card and some case the memory card backup battery go bad it can throw that code.

If back up battery working correct the display should go dark in about 3 to 5 seconds after the source is cut off or disconnected or drop to 0 volts. but if go dark quick then it circuit board related issue ( yes I did heard some circuit board is reading some resduide dc voltage on dc buss for couple seconds so it may stay on just a hair longer )

without the current model numbers I cant really pinpoint the exact spot what you are going thru even thru you did follow the check list very carefully so I am sure you did covered all base on this.


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## JRaef

On the SMC Dialog Plus, the starter needs to see at least 20% of the motor current flowing within 2 seconds of the Start command on all 3 phases. If not, you get the F15 fault. 

I know this can sound insulting, but I'm not meaning it that way because trust me, I've done it myself...

Is there a local disconnect switch at the motor and is it open? :blink:

Assuming not, then other cheap-to-check-out possibilities:


Has one of the CT leads has come off inside of the starter (been there, seen that too)?
Bad contact or connection on the input isolation contactor? Easy to test by jumping around it.


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## gpop

JRaef said:


> On the SMC Dialog Plus, the starter needs to see at least 20% of the motor current flowing within 2 seconds of the Start command on all 3 phases. If not, you get the F15 fault.
> 
> I know this can sound insulting, but I'm not meaning it that way because trust me, I've done it myself...
> 
> Is there a local disconnect switch at the motor and is it open? :blink:
> 
> Assuming not, then other cheap-to-check-out possibilities:
> 
> 
> Has one of the CT leads has come off inside of the starter (been there, seen that too)?
> Bad contact or connection on the input isolation contactor? Easy to test by jumping around it.



Not insulted at all. (rather be insulted by a electrician than look like a idiot in front of the boss)

Disconnect is closed and tested. Contactor has been stripped and checked and when the SS gets a start signal it closes and tests good with a voltmeter. 

The CT are using a adapter and that could be a problem. (not sure how to test)

Jumping around the isolation contactor is a good idea at least i will be able to look in the linear list and see what the control module is seeing. 

Was busy today and no one is screaming for the pump so i haven't got back to it.

At least i know what the SS expects to see and why it takes 2 seconds to fault.


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## frenchelectrican

JRaef.,

Thanks for reminding me about CTs I am not too famuair with smaller units if they are CTed or not but larger ones yes ., I have fount out in hard way I have one soft starter went bonkers and took me a little while to find out why and found out the CT was shorted out ( got uneven reading on the cts ) 

At least we know now what to expect.

Thanks again JRaef.


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## glen1971

Did you megger the motor? Lines to ground? Line to Line? Wiring from the SS to the motor? If you have blown winding, or a bad splice, would that be similar to JRaef's thought on the local disconnect?


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## gpop

glen1971 said:


> Did you megger the motor? Lines to ground? Line to Line? Wiring from the SS to the motor? If you have blown winding, or a bad splice, would that be similar to JRaef's thought on the local disconnect?


All tested good.

Hopefully tomorrow i will get some time to run a few more tests. The motor doesn't attempt to budge when the SS says its starting. I would like to get a voltage reading to see if the SS is putting out anything. Either the voltage is real low and stays low because its not seeing amps or there is no voltage. 
Also would like to try md's plan and run it off a vfd to test it.


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## gpop

OK heres a update.

SS has had the breaker shut down since Thursday (this cuts 120 control power and 480v main power)

This morning i go to the pump and try the fan with a screw driver. Motor is heavy but turns. Defeat the safety so i can open the disconnect with out turning it off. Hook up the recorder to the line side.

Go in the Mcc and turn on the breaker. Go back to the pump and press the start button expecting nothing to happen (just planning to prove to myself that there is no volatge during starting). Bloody pump starts, ramps and runs fine. 

Consider it must be a solider joint in the controller that flakes out when its warm. Test the pump at least another 4 times during the day. Starts every time with out faulting. 

Now its a intermittent problem. That worse than a unknown problem.


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## Cow

gpop said:


> Now its a intermittent problem. That worse than a unknown problem.



I absolutely HATE intermittent problems. Because then I know the customer is going to call back. Later. When it stops working again....


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## MDShunk

Cow said:


> I absolutely HATE intermittent problems. Because then I know the customer is going to call back. Later. When it stops working again....


I think in this case he's the plant electrician, but it still sucks. It's your name on the line. As far as everyone else is concerned, he "got it working", then it will break down again and they'll think he didn't "fix" it right the first time. It just sucks any way you think about it. It would have been better if the thing just melted down in a big blaze, then at least you'd have a black charred mess to point at and could slap a new one it with surety. Actually, there still may be some doubt whether it's the SS or not, at this point. At least there's still a little doubt in my mind yet, I should say.


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## gpop

Yep been in this position before. 

Its got my interest now. This one is defiantly getting the full dissection when it either dies or gets upgraded to something new.


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## gpop

MDShunk said:


> I think in this case he's the plant electrician, but it still sucks. It's your name on the line. As far as everyone else is concerned, he "got it working", then it will break down again and they'll think he didn't "fix" it right the first time. It just sucks any way you think about it. It would have been better if the thing just melted down in a big blaze, then at least you'd have a black charred mess to point at and could slap a new one it with surety. Actually, there still may be some doubt whether it's the SS or not, at this point. At least there's still a little doubt in my mind yet, I should say.



Yep im a plant electrician and ive got about 15 years with the company so i don't have to baffle them with bull****. 

Told them i have no idea how its working and no idea how long it will run for.

They are more concerned that we have a plan B, once it was explained that we have multiply vfds in stock that could be used instead of the SS they forgot all about it and moved on to the next problem.


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## JRaef

gpop said:


> ...
> The CT are using a adapter and that could be a problem. (not sure how to test)...



Sorry, forgot about that, it's been a while since I've played with an old Dialog Plus and I forgot that they needed that "converter module". Yours should be a part # 825-MCM180. But all that is is a set of 3 Hall Effect Transducers and a comm board that feeds a digital signal into the SMC control board, then all of those parts are essentially "potted" into that module. There's no good way to test it that I am aware of. One thing I remember about them though, there is a little cable that connects the 825 Converter Module to the fanning strip of the SMC with an RJ45 connector (I think). Rockwell warned people to NOT try to make their own cable or it will be subject to intermittent failure. The problem was, it was only available as 3ft long and if people wanted to mount the 825 module further away, they would sometimes make up a longer cable themselves. Check that cable to see if it looks home made, and/or see if it is loose, has corroded connection pins, etc., anything that might be intermittently interrupting that signal telling the SMC what the current value is. before you replace the entire soft starter, you may want to replace just that 825-MCM180 unit first. I'm pretty sure you can still buy them because they used them for other things beside the old SMC Dialog Plus.


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