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Star Delta Connection

6129 Views 13 Replies 10 Participants Last post by  bennysecond
Hello,
I hope every body is good there. Well i am installing one 37kW load Star-delta motor. when my motors turns from star to delta connection my ELCB which is 4 pole 63/30mA trip. rest of all the isolator and MCB remain same. when i disconnect all the wires from the terminal block and run my panel then there is no trip in the circuit.

i connect my six wires properly and checked my star connections which are ok...
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It's not uncommon for this to happen, it has to do with the phase shift that takes place in the transition and whether or not the magnetic field in the motor has collapsed, and/or whether the motor slows down during the open transition.

The shortest route to a solution is to scrap the star-delta starter and install a solid state soft starter, it will not have this issue and is better for the motor and load. All other potential solutions involve having someone with experience in this issue being there with the motor and starter to troubleshoot it, because it could be any of a large number of issues, or ultimately it may be that star delta will never work for your application. But you will not know until you have spent countless hours trying other solutions. So it comes down to you deciding wh[p]ether your time is more valuable than the hardware.
 

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Hello,
I hope every body is good there. Well i am installing one 37kW load Star-delta motor. when my motors turns from star to delta connection my ELCB which is 4 pole 63/30mA trip. rest of all the isolator and MCB remain same. when i disconnect all the wires from the terminal block and run my panel then there is no trip in the circuit.

i connect my six wires properly and checked my star connections which are ok...
Have you checked the contacts on both starters? Is the star dropping out? I'd check some of those things first. Has the machine ever run correctly or is it a new machine?
 

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Sir this is a brand new machine..
I like the sir part:laughing::laughing: Couldn't tell that in your original post. What type of machine are you installing it on? Just curious because the machine's I've seen with star/delta starters come as a package and I presume someone test runs them before release.
 

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I'm not sure I'm understanding the problem correctly. Is the problem that the GF breaker is tripping during the switching from star to delta?
 

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Discussion Starter · #9 ·
Tripping of ELCB

I'm not sure I'm understanding the problem correctly. Is the problem that the GF breaker is tripping during the switching from star to delta?
Can any one please guide me what are the main cause of 4P ELCB tripping in a circuit in which i have one three phase machine running with 3core cable while neutral is only using inside the panel for control purpose such as contactors and indication lamps.
 

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Can any one please guide me what are the main cause of 4P ELCB tripping in a circuit in which i have one three phase machine running with 3core cable while neutral is only using inside the panel for control purpose such as contactors and indication lamps.
You have an intermittent fault. A tough condition to track down.

Or, you have a bad circuit breaker?

Is the neutral on the control transformer grounded? If so, could you have some "leakage" at this ground point that is causing the GF to trip?
 

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megger test

we have the same problem in s-d starting of a 200KW induction motor which drives a fan. just in star to delta transition the 400A Simens MCCB trips. then we replace that motor with another and every things get OK.
check your motor insulation resistance with a megger. maybe one phase insulation broken and it leads the current to ground in transition and your ELCB trips.
regards,
reza mohandes.
 

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It's not uncommon for this to happen, it has to do with the phase shift that takes place in the transition and whether or not the magnetic field in the motor has collapsed, and/or whether the motor slows down during the open transition.

The shortest route to a solution is to scrap the star-delta starter and install a solid state soft starter, it will not have this issue and is better for the motor and load. All other potential solutions involve having someone with experience in this issue being there with the motor and starter to troubleshoot it, because it could be any of a large number of issues, or ultimately it may be that star delta will never work for your application. But you will not know until you have spent countless hours trying other solutions. So it comes down to you deciding wh[p]ether your time is more valuable than the hardware.
Not everyone can just pull out a factory install 3 contactor start system and its associated wiring system and install a soft start.

OP. This is the very most common issue with 6 and 12 lead motors.
Connecting the motor correctly.
If the motor starts in wye and trips when it tries to go into delta config,
the motor is connected wrong.

9 times out of 10 it is the phasing on the transition.
I have been working around motors my whole career and I can honestly say that incorrect motor connections are the most common reason.

If the motor will run in any configuration, the motor is not the issue nor is it your breaker.

What size breaker do you have in front of this motor?
Its FLA X 2.50 for maximum breaker size.
 

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Why do you use 30mA breaker?
Is that have to protect people?
Is it mandatory in your local code book?
what about 4P 63A/300mA

added: I assume you have TT service as neutral is also protected
I had came across that kind of systems and never have seen 27kW motor on 30mA. In fact there was 300mA for main protection and sub main 30mA for outdoor and humid spaces (Residential). For Industrial you have even higher mA breakers (125, 500, 1000 etc). Beside you have extra breakers with e.g. D curve for peak current during start or other required by manufacturer. Or special set just for machine.
e.g. DPX series from Legrand for Industrial application:
http://www.legrand.se/se/scripts/se/publigen/content/templates/previewMultiPhoto.asp?P=485&L=EN

good luck
 
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