Improved Starting Process Alternative to Conventional Star-Delta Switching of A-C Meters

For the purpose of reducing mechanical shocks caused by the sudden increase of torque, and to avoid high current transients as a result of the interruption of supply in the conventional stardelta switching, an alternative starting process is presented here. It is proposed to start the motor on the unbalanced-delta connection in which a resistance is inserted in one of the lines feeding its delta-connected stator. When the running speed has been reached, the resistance is bridged to permit normal balanced running. It is also proposed to use the unbalanced-delta connection as an intermediate step in star-delta switching. In this respect, the once suggested open-delta connection is proved unsuitable for this purpose.