Star-delta cam switch

The YΔ circuit is used to start larger three-phase motors with squirrel-cage rotors at reduced power consumption. This prevents overcurrent protection devices from tripping due to the otherwise high starting current during direct starting.
In this starting procedure, the three-phase motor is initially connected in a star connection, then subsequently in a delta connection. The motor's power consumption during starting in star connection is one-third of the power in delta connection. The Y-Δ switching has become largely obsolete due to the use of frequency converters. Unlike Y-Δ switching, frequency converters allow for reduced current consumption while still achieving high starting torque.

Reversing switch as cam switch

Three-phase reversing switches are used to reverse the direction of rotation in three-phase motors. During the switching process, two phases of the three-phase power supply are swapped, causing the motor to start in the opposite direction. Typically, all three phases are switched, and in the "0" position, the motor is completely disconnected from the power supply. In the next step, the motor is switched back on with two phases reversed.