The Carlo Gavazzi DWB01 Monitoring Relay is used for monitoring the actual load of asynchronous motors and other symmetrical loads, where the power factor is almost proportional to the load. The desired function can be set via adjusting the four DIP-switches, which can be accessed by using a screwdriver to open the plastic cover.

The relay measures the power factor (cos ϕ) ratio between the active and apparent power of the motor. A manual switch can start and stop the motor without the need for an auxiliary device. As cos ϕ varies with the load of the motor, underload and overload can be indirectly detected by the DWB01. The relay also has an adjustable power ON delay to avoid overload detection during motor start.