Star-delta starting of three-phase induction motors
Table of Contents
ToggleThe problem of each three-phase asynchronous motors is its high starting current, which can be about 7 to 10 times the rated current. Therefore, big 3-phase induction motors from 4 kW should only start with starting aids. Star-delta starting (in short YΔ-starting) is one possibility.
In the European supply network, the voltage phase to phase is 400 V. That means, the winding of this induction motor must be rated for 400 V to apply YΔ-starting.
Here, the three-phase motor starts in star, then after a certain time, the motor is switched to delta:
![3 Phase Induction motor Star-Delta starting circuit](https://sp-ao.shortpixel.ai/client/to_auto,q_glossy,ret_img,w_1219,h_620/https://learnchannel-tv.com/wp-content/uploads/2019/04/3-Phase-Induction-motor-Star-Delta-starting-circuit.png)
3 Phase Induction motor Star-Delta starting circuit
Problem of YΔ-starting: The torque in star is 1/3 of torque in delta. Perhaps the motor cannot start with full load. Also, consider that starting with reduced power can lead to a longer acceleration time.
![3 Phase Induction motor – Star-Delta torque-speed-current curve](https://sp-ao.shortpixel.ai/client/to_auto,q_glossy,ret_img,w_452,h_277/https://learnchannel-tv.com/wp-content/uploads/2023/01/3-Phase-Induction-motor-–-Star-Delta-torque-speed-current-curve.png)
3 Phase Induction motor – Star-Delta torque-speed-current curve