What is a Star Delta Starter?

What is a Star Delta Starter?

Star triangle starter set

The star triangle starter is used to start a three-phase induction motor by starting in a "star" configuration and then switching to a "triangle" after reaching a certain speed, thereby minimizing initial electrical overload.

Circuit diagram

The circuit includes a TPDP switch that helps to change the motor connection from a star to a triangle, thereby effectively controlling current and torque during startup. For that let us consider,

VL = Supply Line Voltage, ILS = Supply Line Current, IPS = Winding Current per Phase, and Z = Impedance per phase winding at standstill conditions.

The formula shows that the star-shaped triangle starter reduces the starting torque to one-third of the starting torque generated by the DOL starter. The star triangle starter is equivalent to a self-motor transformer with a tapping rate of 57.7%.

Advantages of Star Delta Starter

• Cheap

• It does not generate heat and does not require a faucet change device, thus increasing efficiency.

• The starting current is reduced to 1/3 of the direct online starting current.

• High torque per ampere line current.

Disadvantages of Star Delta Starter

• The starting torque is reduced to 1/3 of the full load torque.

• You need a specific set of motors.

Application of Star Delta Starter

• As described above, the Star Triangle starter is best suited for applications where the required starting current is low and line current consumption must be at a minimum.

• The star triangle starter is not suitable for applications requiring high starting torque transmission. For these applications, the DOL starter should be used instead.

• If the motor is overloaded, there will not be enough torque to accelerate the motor to speed before switching to the incremental position. An example application of a star-triangle starter is a centrifugal compressor.