The Star-Delta 3-phase Motor Starting Method

The Star Delta starting method is a motor starting mechanism that minimizes the large amount of starting current that motors draw in. The Star Delta, as the name suggests basically involves feeding the motor with 1/sq. root3 (58%) of the full load current until it attains speed then applying the full load current. This method is commonly referred t
The Star-Delta 3-phase Motor Starting Method - schematic

o as "Soft Starting" the motor, For this to work the whole set-up requires 3 contactor i. e The Star Contactor, The Delta Contactor & The Main Contactor. However for the motor to be started in Star Delta, its internal connection at the terminal box has to be wired in Delta-giving it capability of receiving the full-load current at any instant. Traditionally, in many regions there was a requirement that all motor connections be fitted with a reduced voltage starter for motors greater than 4KW 5HP. This was to curb the high inrush of starting currents associated with starting induction motors.

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