Star-delta (wye-delta) starting

Star-delta (wye-delta) starting can only be used if the motor normally operates in a delta connection or starts softly, or if the load torque is low and does not rise sharply during star starting. In the star (wye) stage motors can be subjected to around 50 % (torque class CL 16) or 30 % (CL 10) of their rated torque; the starting torque reduces to approximately 1/3 of the value on direct closing. The starting current is approximately 2 to 2.7 times the rated motor current.

The switchover from star (wye) to delta cannot be carried out until the motor has been fully accelerated to the rated speed. Drives which require this switchover to be performed earlier are not suitable for star-delta (wye-delta) starting.

The rated power levels apply to motors with a starting current ratio of I_A в‰¤ 8.4 x I_N and when using a 3RT1916-2G or 3RT1926-2G solid-state time delay auxiliary switch block with wye-delta function, or a 3RP2574 wye-delta time relay with a changeover delay of approximately 50 ms.