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Topic Title: Star- Delta Motor
Topic Summary: Issue With tripping on change over.
Created On: 28 September 2017 12:38 PM
Status: Read Only
Linear : Threading : Single : Branch
 Star- Delta Motor   - RichardElliott - 28 September 2017 12:38 PM  
 Star- Delta Motor   - ToniSM - 28 September 2017 03:57 PM  
 Star- Delta Motor   - RichardElliott - 28 September 2017 08:24 PM  
 Star- Delta Motor   - whjohnson - 28 September 2017 10:29 PM  
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 28 September 2017 12:38 PM
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RichardElliott

Posts: 3
Joined: 15 September 2016

I'm looking for some help regarding an issue with a Star delta motor/ starter.

To give some background to this I was asked to re-terminate a motor that had been disconnected and replaced with a new one by a mechanical team.

I had originally terminated the star side of the motor as per usual (U1=L1 V1=L2 W1=L3) however this caused the motor to run in reverse.

So I then swapped the L1 & L3 phases to allow the motor to run to the correct rotation. (U1=L3 V1=L2 W1=L1).

This worked so I then altered the Delta side of the motor accordingly (U2=L1 V2=L3 W2= L1) However this caused the MCB in the panel to trip on change-over from Star to Delta.

My question is

1)Is the above wiring/ modification correct? If not, how would I need to modify it.
 28 September 2017 03:57 PM
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ToniSM

Posts: 339
Joined: 21 November 2006

Put them back as you first connected them and then swap the feed to the contactors.

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Could there be a better way?

In theory yes, but in practice?
 28 September 2017 08:24 PM
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RichardElliott

Posts: 3
Joined: 15 September 2016

Thanks ToniSM
 28 September 2017 10:29 PM
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whjohnson

Posts: 934
Joined: 24 January 2009

You say the motor has been changed?
Is the replacement motor of the same rating as the original? If not, you may have to look at changing the ratings of contactors/overload units, cable sizes etc to accommodate.

As you have found, if you swap phases on the star side only, the motor will try to reverse itself when it changes over to delta, which would cause a momentary overload and subsequent trip-out. So swap only the mains side as suggested.

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Political correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.
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