# Need Ideas - Brain Locked



## Angus (Jan 27, 2011)

Ok,

Here is the situation, I have two 100 HP motors on the same shaft powered by 480v 3ph. I have a MCC with two sz4 starters interlocked with each other. A single start stop for control with a system that monitors belt slip and alignment and the motors built in PTC probes. 

So far no problem.......

Due to the huge inrush currents with both motors starting at the same time....I have sold my customer on installing a pair of soft starts. This is where the issues I am having starts. 

I need to wire as per the above scenario but also include the SS. Additionally, I want to include a soft start bypass switch to allow to run off the mechanicals if a SS would fail. 

What I was thinking was that instead of having several relays to switch all of the control items install a small simple PLC (such as a CLICK) to handle these issues with only needing 4 outputs (2 for the SS and 2 for the Mechs).

I am over complicating this? A simpler way?

BTW The SS are Square D Altistart 48 .

Thanks, Angus


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## oliquir (Jan 13, 2011)

plc is the way to go, i hate when electrician put a lot of relays to make logic controls.


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## John Valdes (May 17, 2007)

You can design the control scheme to your liking. I like the idea of a small PLC. But it does sound awful simple. Each soft start has its own inputs and the need for several relays may not be required.
I would have not purchased Square D, but you have them now, right? The bypass should be discussed with the SS manufacturer before the purchase. This should have been part of the SS package. 
You could have bought the SS and bypass in their own enclosure. Then all you had to do was connect your interlock.
You are just going to have to work with what you have. Start with a drawing and make sure it works on paper. Then make your material list from the drawing. Good luck.


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## Angus (Jan 27, 2011)

Looking back at the decision on the SS.....I agree I wished I wouldn't have bought the Square D. 

Any opinions on the Click brand of PLC's ---> http://www.automationdirect.com/adc...s_(Stackable_Micro_Brick)/PLC_Units/C0-01AR-D

Thanks


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## Angus (Jan 27, 2011)

Looking back at it I wished I didn't buy the Square D Starters.....

How does the Click PLC stuff stack up.......http://www.automationdirect.com/adc...s_(Stackable_Micro_Brick)/PLC_Units/C0-01AR-D

Thanks again


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## oliquir (Jan 13, 2011)

i would personally go with this one http://www.automationdirect.com/adc...tLogic_05_(Micro_Brick_PLC)/PLC_Units/D0-05AR since relay output are more beefier
the click relay output (1A max) rating are small for 100hp contactor coils (ive burned some driving some hydraulic valve coils)
but the click is ok if you use external relay to drive contactor coils
also the click needs 24V supply and not the dl-05


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## John Valdes (May 17, 2007)

I would go with Weg. They make their bread and butter on soft starts and motors. 

http://www.weg.net/us/Products-Services/Drives/Soft-Starters

These guys got it goin on. They will build it for you if you want. To your specs. Take a look at the web site and see if they are not the leaders in soft starts and motors.
Look at the options. No one does it like they do. Maybe Benshaw, but not as good as Weg.


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## JRaef (Mar 23, 2009)

You didn't post the nature of the machine, and it makes a BIG difference. 

I have done countless dual-motor-common-shaft systems and in fact developed a standard option for that for a soft start manufacturer. Basically you must FIRST determine if the machine / process can start with one motor and just needs the second one AFTER it gets to speed, or if you need the starting torque of BOTH motors in order to accelerate it. If it's the latter (both motors to accelerate it), then you cannot put soft starters on at all. Forget it, it's a fail waiting to happen. Your ONLY option in that case is going to be a VFD big enough to accelerate moth motors, i.e. a 200HP VFD in your case.

If, as is USUALLY the case on these types of systems, one motor will accelerate it because it is unloaded, then there are two directions you can take:

1) Don't deal with the soft starters yet, try tuning on motor one, then after the machine accelerates, turn on motor 2. If it was the starting current of BOTH motors together that was overloading your system, then this will likely cure that problem, and if that's the only problem you need to cure, you are done.

2) If you still have a problem with system capacity, try putting a soft staerter on motor one, again wait for it to acceklerate the load, then close starter 2. Because the motor is already spinning, all you will have is magnetizing inrush; high peak, but 2 cycles long, usually not enough to trip breakers etc.

In either case it's important to interlock this scheme with whatever feeds into the machine to make sure the infeed is delayed until AFTER the second motor is connected and at full power.

Putting soft starters on both motors will never work, they will never share the load anyway, so one will be dragging the other, meaning the soft starter on the second one was a complete waste. If anything, put in ONE BIG soft starter and start them both together. You will need separate OL relays and possible separate breakers, which tends to make it not worth doing. But in my extensive experience with this, the end result is no different tha option 2 above.


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## JRaef (Mar 23, 2009)

John Valdes said:


> I would go with Weg. They make their bread and butter on soft starts and motors.
> 
> http://www.weg.net/us/Products-Services/Drives/Soft-Starters
> 
> ...


Weg motors, fine. But my opinion of the Weg soft start is not as high, albeit we all have our own experiences and preferences. Mine comes from the fact that Weg, when they wanted to bring their soft start to the US from Brazil, was looking for a US based mfr to assemble it and take it through UL for them. But they wanted to control the design and components. We (my employer at the time) considered doing it, but when we got units to take a look at, they were _very_ marginally designed and we decided we didn't want our name associated with that product even indirectly. We declined, and gave them suggestions for improving it for the US market (probably not a great move, but what the heck). The outfit they selected does an OK job and Weg seems to have taken some of that advice, but since then I have sold a couple of them on rock crushers (a subsequent employer owned a Weg distributorship) and I was unimpressed. They didn't die, but the setup was a struggle and I know a lot more about that than most people do.

But I will say this, they are UNEQUIVOCABLY better that the AntiStart 48!

Again, just my opinion...


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## John Valdes (May 17, 2007)

And your soft start of choice?


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## JRaef (Mar 23, 2009)

John Valdes said:


> And your soft start of choice?


Whoever is signing my paycheck... ;-)

Seriously, in no particular order and even though in some cases I can't stand the PEOPLE, but I'm being fair about the products:
I like A-B (my current paycheck provider, but I don't work for that division), Motortronics, Benshaw, Solcon and SAF Canada ( not Saftronics who are all but gone now). ABB is OK, they copied Motortronics but their Swedish version is OK too, just difficult to use. GE looks ok too, I just have never used one. Aucom (Danfoss) makes both good and really crap products. The Weg is ok, just not top tier IMHO. 

My "run the other way" list is Sq. D / Schneider, Cutler Hammer, and most of the small "energy saver" scammers. 

All the others are marginal at best.


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## Netree (Sep 3, 2011)

Angus said:


> Looking back at the decision on the SS.....I agree I wished I wouldn't have bought the Square D.
> 
> Any opinions on the Click brand of PLC's ---> http://www.automationdirect.com/adc...s_(Stackable_Micro_Brick)/PLC_Units/C0-01AR-D
> 
> Thanks


Very bad. I would use the Zelio from Schneider; 5 amp contact rating, 6 inputs, 4 relays output. SR2A-101FU is 120-240 VAC powered. I use many of this type and none have failed.

http://www.grainger.com/Grainger/ww...a101fu&op=search&Ntt=sr2a101fu&N=0&sst=subset

Software and manuals you download free, cable is cheap. This can be programmed from the keypad. :thumbsup:


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## John Valdes (May 17, 2007)

JRaef said:


> Whoever is signing my paycheck... ;-)
> 
> Seriously, in no particular order and even though in some cases I can't stand the PEOPLE, but I'm being fair about the products:
> I like A-B (my current paycheck provider, but I don't work for that division), Motortronics, Benshaw, Solcon and SAF Canada ( not Saftronics who are all but gone now). ABB is OK, they copied Motortronics but their Swedish version is OK too, just difficult to use. GE looks ok too, I just have never used one. Aucom (Danfoss) makes both good and really crap products. The Weg is ok, just not top tier IMHO.
> ...


The reason Weg is my first choice for soft starts is availability, quality, technical support, custom control panels and crusher duty products.
Weg is my top choice in aggregate. That is where I made my bread and butter. I like the ability to build a soft start with bypass and the control the way I want it from the catalog. I also had a very good working and personal relationship with Weg along with few other manufacturers.
Going to Brazil for a week did not hurt my relationship at all with them. Impressive would be an understatement. They were easy to work with and extremely knowledgeable about there equipment. Not as knowledgeable about their customers needs. But they were doing better as they have not been in this market as long as the other big names.
Benshaw is similar in that aggregate company's are particular about what they install in their quarry's and plants. They want heavy duty reliable equipment and immediate relief on shut downs. With Weg and Benshaw I could provide this to them 24-7. I could also provide extended warranty when they purchased motor and SS/drive together.
Sometimes service trumps everything else. 
I have been out of this business for over 5 years now. So you have an advantage as you are working with the equipment every day. Like I used to.

One more thing that really made Weg an excellent choice. Price.


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