Three phase pole-changing motor - changes from delta to double star configuration with soft run=up by delaying connection of star point

摘要

In pole changing motors using a change from delta to double star connection between low speed and high speed the starting current in the high speed condition can be very high. This current is reduced by introducing a time delay between the closing of the paralleled windings ends (1-6) onto the supply (8, R, S, T) and closing the star point forming contactor (9). With the star point open the motor starts with reduced torque in a quasidelta connection but with the correct pole number. At the selected time interval the solid star point is made and the motor is available for full output.