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Star and delta connections

Star and delta connections A three-phase electric motor can be connected in two ways, star (Y) or delta (A). The winding phases in a three-phase motor are marked U, V and W (U1-U2; V1-V2; W1-W2). With the star (Y) connection the "ends" of motor winding's phases are joined together to form a zero point, which looks like a star (Y).
On the motor plate it can, for example, state 690/400 V. This means the star connection is intended for the higher voltage and the delta connection for the lower. The current, which can also be stated on the plate, shows the lower value for the star connected motor and the higher for the delta connected motor.
The main supply is connected to a three-phase motor's terminals marked U,V and W. The phase sequence is L1, L2 and L3. This means the motor will rotate clockwise seen from "D" the drive end. To make the motor rotate anticlockwise, two of the three conductors connected to the starter or to the motor are switched. Check the opperation of the cooling fan when rotating anticlockwise.