Why star delta starter is used? Explained


why star delta starter is used, advantages of star delta starter


Star delta starter is mainly used to reduce the flow of current at the starting of the three-phase induction motor to avoid sparking, overheating, coil burning, etc. Now it is most important to understand that how a star-delta starter reduces the starting current of the induction motor. The concept is very simple, in the star connection phase voltage is lower than the delta connection. 

So basically star delta starter has both the star and delta connection arrangement and also it has a timer. So at the starting time, the motor is connected to the Start connection. After few seconds which already set in the timer motor will connect from the star to the delta connection.

So, at starting time star connection helps to reduce the starting current and in the running condition, the delta connection helps to gather enough torque and speed for the motor.



What happens if the Motor is connected to Delta connection at starting?

The secondary or rotor coil of the induction motor always short-circuited. So if the motor is connected to the delta connection, it will get a very high voltage to the winding, the motor will draw a very high current which may cause the burning of the coil.



What happens if the motor is always connected to the Star Connection?

Now, you may think why need to change the star to delta connection, what happens if the motor is always run with the star connection. We know that the speed and torque of the induction motor are directly proportional to the square of the supply voltage. So if we increase the supply voltage, speed and torque also be increased. For this reason, once the motor is started with a normal speed it changed to a delta connection to gather more speed and torque.



What is the Difference between Star Delta Starter and DOL Starter?

DOL starter means Direct On Line Starter. It only helps to start and stop the motor. With a DOL starter, the motor only connected with the Star connection or Delta Connection. It does not change the connection. DOL starter does not reduce the starting current. DOL starter provides the same voltage to the motor at both starting and running conditions. 

On the other hand, Star delta starter can reduce the flow of current at starting. It starts the motor with a star connection and runs the motor with a delta connection. Star delta starter is used with an induction motor above 5 KW. Star delta starter is more expensive and complex designed than DOL starter. 


Advantages of Star Delta Starter

1. Reduce the flow of current at starting which avoids the chances of sparking, overheating, burning of the coil, etc.

2. It helps to gather more speed and torque to the induction motor at running conditions.

3. Star Delta starters are most suitable for large and high power induction motors.

4. Star delta starter provides more electrical safety and a greater life span to the induction motors.


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Why star delta starter is used? Explained Why star delta starter is used? Explained Reviewed by Author on 5/25/2021 Rating: 5
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