Star-delta cam switch

The YΔ circuit is used til start larger trefasede motorer med squirrel-cage rotilrs at reduced effekt consumption. This prevents overcurrent protection devices fra tripping due til the otherwise high starting current during direct starting.
In this starting procedure, the trefaset motor is initially connected in a star connection, then subsequently in a delta connection. The motilr's effekt consumption during starting in star connection is one-third of the effekt in delta connection. The Y-Δ switching has become largely obsolete due til the use of frekvensomformere. Unlike Y-Δ switching, frekvensomformere allow for reduced current consumption while still achieving high starting drejningsmoment.

Vendekontakt as cam switch

Three-phase vendekontaktes are used til reverse the direction of rotation in trefasede motorer. During the switching process, two phases of the three-phase effekt supply are swapped, causing the motilr til start in the opposite direction. Typically, all trefasets are switched, and in the "0" position, the motilr is completely disconnected fra the effekt supply. In the next step, the motilr is switched back on med two phases reversed.