Motor protection switch

The motor protection switch protects a motor from overload and failure of an external conductor by monitoring current consumption. Motor protection switches used for three-phase motors typically integrate OR release logic in the three supply lines, which are monitored thermo-mechanically (bimetal), hermo-electronically (PTC resistor) or electronically (current measurement).

Restarting after tripping can take place automatically or manually by pressing a reset button.

Short-circuit trips, which are not actually required for motor protection, are also frequently installed to protect the power supply from short circuits. In accordance with DIN VDE 0100 they must be positioned at the start of a motor supply line.