How to determine the star Delta change over time ?

Hello rseee

Do you mean the time between closing the star contactor to the change over to delta, or due you mean the time between opening the star and closing the delta contactors?

The starter should remain star connected until the motor has reaced full speed, or run out of acceleration torque. NB in many cases, the motor does not produce enough torque in star to get the load to full speed, so the changeover happens at part speed.

Have a look at Motor Starters and Star Delta Starters

Please note, the more specific the question, the better the answer, and the more likely you are to get an answer.

Best regards,
Mark

You means to say that the Delta changeover time to be set as per the practical conditions.
That is Time taken of the motor to reach 50% of the rated speed.
Please correct me if i understood wrong.

Hello rseee


If the starter steps to delta at half speed, there will be a high start current in delta and there is no advantage of using a star delta starter over a DOL starter.

The delta change over time is set to the actual installation and it is set to change over when the motor is at full speed except where there is not enough torque to reach full speed.

Best regards,
Mark.