Electric Motor Star and Delta Connection Diagrams

by Editor on August 17, 2012

These diagrams show the basic 3 phase electric motor coil winding configurations for Star and Delta connections.

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The first shows that a Star connected motor will draw less current than when it is connected in Delta.

Electric Motor Star and Delta Connections Diagram

(Double ckick the image twice to enlarge)

The diagram below shows the actual wiring and link connections for both Star and Delta to a typical Squirrel Cage electric motor.

Note that most electric motor coil windings are labelled U,V and W and the end of each winding is indicated as 1 or 2 ie. U1-U2…

When wiring the motor you will need to fit the links in the motor connection box to configure them for either Star or Delta. The link connections options are normally shown on the motor or inside the connection box lid.

Most basic fan motors will be connected for Star configuration.

To change the direction of the motor simply swap any two phase connections.

Electric Motor Star and Delta wiring and Link Connections Diagram

Star Delta Motor Starter

Where a Star Delta Motor Starter is used all 6 motor terminals are connected as per the wiring diagram of the starter unit.

The motor will be started in Star and switch to Delta when the motor reaches its normal running speed.

This is to reduce the start-up current draw of the motor which can be up to 4 times the running current.

Thanks for the diagram to: Rotor UK Ltd. 16 Everitt Close, Denington Industrial Estate Wellingborough NN8 2GF

More info about Electric Motors.


{ 7 comments… read them below or add one }

Magnumswitchgear September 5, 2018 at 07:25

Hi, very useful blog helped me lot. Thanks Geoff

jayakarthick July 1, 2018 at 06:46

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Araav March 10, 2018 at 10:42

Professional, efficient, experienced.
Thank you for your guidance. I searched for a long time the star and delta connections.

chris March 5, 2015 at 19:19

good blog here,
but how do we reverse a star delta wired motor, as iv tried all sorts but nothing seems to work correctly?

Geoff Dye December 14, 2014 at 08:41

Hi can you help please. I have a three phase lathe but only have single phase available to the house. Im contemplating fitting a single phase to 3 phase VSD to overcome this.
This will require a bit of rewiring.
A. I intend to firstly change the motor from star to Delta as the VSD is only 230 v 3 phase output. Am I correct in my thinking on this.
B. I intend to connect the VSD directly to the motor and switch the single phase input not the 3 phase output so as there is a load on the 3 phase output at all times when energised so as not to have run away voltage ( blow up ) due to no load. IS this a good idea. I was thinking of using an on/ off and E stop push buttons control a relay for connecting and disconnecting the VSD supply.
C. Forward and rev. I intend to use the existing forward revers contactors and controls that exist as switches only, to switch the input /outputs forward / Rev contacts inside the VSD.
however im not sure how to wire in the inching, jogging control?
A review of this and any suggestions would be greatly appreciated a simple but safe inching circuit would be much appreciated. Thanks Geoff

Onota Adeiza January 13, 2013 at 08:46

This is a one stop solution. it has really helped. regards.

Andy Ward November 16, 2012 at 10:44

Thanks for giving sparks this blog.
It’s a really useful source of info.

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