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What is a star delta starter?

Star delta starters are another device that may be used to reduce current demand during motor startup. It is often used for starting three-phase induction motors, but can only be used when starting the motor without load and when the required starting current is relatively low.

Star delta starters are asynchronous motor starters that are used primarily to control the starting and running of asynchronous motors. Most induction motors are started by a direct in-line starter, which connects the induction motor directly to the power supply and allows the motor to start at full voltage. However, when starting large motors, due to the high starting current, they can cause voltage disturbances to the power supply line, potentially causing damage to the motor and the power supply. To avoid this, large induction motors need to be started at reduced voltage to limit the starting current. Star delta starters reduce the voltage across each winding by starting the motor with a star connection, where the motor windings are connected in a star configuration, and then switch to a triangular connection after the motor reaches a certain speed. This reduces the starting current and torque and can result in a safer motor and power supply.

Considerations for using star delta start

In general, large Induction motors require star-delta starting, but whether to actually use star-delta starting cannot be judged solely on the basis of the size of the motor power, but also the load of the motor. If the induction motor is lightly loaded during starting and heavily loaded during running, a star-delta starter can be used. Usually, the starting current of squirrel cage motors is much higher than the running current, and a star delta starter can be used.


A star delta starter is a starter used to control the starting and running of induction motors. Using a star delta starter reduces starting current and torque, helping to extend the life of the motor and power supply, making it a cost-effective option in the long run.

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