Star Delta or Wye Delta Motor Wiring Configuration - A basic how to guide

The previous article which covered the star delta motor control power circuit for industrial process control presented an electrical diagram showing the interchanging motor wiring configuration for a star connection and a delta connection using magnetic contactors as motor starters. Exploring further with reference to the previous star delta power circuit diagram, if you manually trace each line connections going to the motor you will begin to understand how the following star and delta motor wiring connections are achieved.

Motor Terminals Before Wiring Connection

Normally, an AC induction motor have six wiring terminals, U1, V1, W1 for the primary terminals, and U2, V2, W2 for the secondary terminals. The start coil where the motor's coil winding starts is marked by a dot (see drawing on the right) to represent each primary starting ends of the three internal motor coils. These starting coil windings are designated with the number 1 following each three phase terminal which are alphabetically represented with U, V, W, so then the primary terminals are named U1, V1, W1. Correspondingly, the other end of each coil is designated with the number 2 to represent the completed end of the coil where each winding comes to a finish, each of these finish ends which are designated with the number 2 are also alphabetically and numerically represented to identify them as the secondary terminals U2, V2, W2.

In the field of industrial process automation control technology, it has always been a common safe practice before doing the actual wiring installation of the electric motor to firstly check for the continuity on both ends of each coil using an ohm meter to verify that U1 meets with U2, and V1 meets with V2, and W1 with W2.

Motor Connected in Star (Wye) Configuration

The AC induction motor's wiring terminals can be configured in either the star connection or the delta connection. The star wiring configuration is connected by shorting all the secondary terminals U2, V2, W2 together while connecting all the primary terminals U1, V1, W1 to the supply source voltage L1, L2, L3. This is achieved by the star delta control circuit which initially activates the main contactor and the star contactor simultaneously while leaving the delta contactor inactive during the startup run sequence of the motor from standstill.

Motor Connected in Delta Configuration

The delta wiring configuration of the motor, which resembles a triangle, is connected by joining U1 and V2, V1 and W2, W1 and U2, while also connecting each of these joined terminals to each of the supply source voltage L1, L2, L3. The delta configuration is achieved by energizing the main contactor together with the delta contactor while disengaging the star contactor.

Learn more about the proper phasing sequence in accordance to a conforming orderly configuration for a star delta motor control wiring configuration.