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star delta starter wiring differences

star delta starter wiring differences

star delta starter wiring differences

(OP)
I have a strange problem, where I have 2 wiring methods for star/delta starter for (18Kw)squirrel cage motor.
the first method is working correctly in case of the transformer or the generator is the main supply.
but the second method is working only when the transformer is the main supply.
but in case of the generator is the main supply, the pump made a disturbance in the power system at the transition from star to delta and the pump is fallen down
all methods are shown in the attached

RE: star delta starter wiring differences

It's very difficult to follw their logic in what appears to be the original design (no hand written changes). It's way more complicated than it needs to be. So the first one appears to be someone's idea of simplifying the circuit. Both circuits are functionally operable as you have noticed, but the original circuit's unnecessary complexity may have made it susceptable to a voltage drop caused by high starting current when used behind a generator with limited capacity, so the sequence became incomplete. My suspicion would be that KA1 NC interlock circuit on the left side, and all the added control circuit paths it entailed. That is also what it looks like the redesign eliminated.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln  
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RE: star delta starter wiring differences

Keep in mind that open transition Star-Delta starting can and will, often shock the network badly. Causing severe transients that could easily trip the generator protection.

A soft starter would be far better for generator starting.

Keith Cress
kcress - http://www.flaminsystems.com

RE: star delta starter wiring differences

The part of the circuit that matters is the part immediately concerned with the transition timer, the shorting contactor and the delta contactor. This part of the circuit is identical. I suspect a timing issue or, as jraef suggests, a voltage drop issue.
Bearing itsmoked's comment in mind, a small change in timing may cause a big change in system upset.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: star delta starter wiring differences

The reason I surmised that it was a VD issue is because he says that the modified version DOES work with the generator, the original one does not. As we see they are both functional, so the only thing I could see that might make the original version fail on a genset would be a loss of the control integrity during transition.

But certainly if there were a difference in the timer settings that could do it too Bill. Good catch.

And Yes, Keith, you are absolutely right about a SS being a better chioce. I am usually one who rails against Star-Delta as a starting choice, I don't think it provides ANY positive benefit, only risk, so there is no "up side" to choosing it. I don't know why I let that opportunity slip by me this time wink


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln  
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies  

RE: star delta starter wiring differences

(OP)
I'm completely agreed with you about VD, but the cause of this failure is vague and can't be explained.
in other words, why it didn't happen with the modified one?
that means there is a small difference between the two methods, what is this?
regarding "KA1 NC interlock circuit on the left side" it is used only in Automatic mode starting and has no function in manual mode.
the problem was done in manual or automatic mode all the same.   

RE: star delta starter wiring differences

Hello mkhalifa09
One question, are these two circuits being used on the same motor and pump assembly, or do you have two motors, one using method 1 and the other using method 2?

From the circuits, I do not see nay reason why one circuit should be any different from the other in a manner that would consistently cause one method to operate and the other trip.
Both methods can cause very high current and torque transients.

Best regards,

Mark Empson
L M Photonics Ltd

RE: star delta starter wiring differences

(OP)
I tried the two circuits on the same motor and pump (submersible pump)    

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