Electrically driven liquid pump e.g. for wet cleaning machine

摘要

A device to monitor an electrically driven liquid pump in a wet cleaning machine has a switch (20) in the supply circuit (14) to the motor (10) with a controller 940). This generates a pulse-shaped control signal with variable mark/space ratio. A measurement circuit (50) is connected to the motor and in the time periods when the power to the motor is interrupted, this circuit measures the generated voltage. An evaluation circuit (60) takes this voltage as representative of the rotation of the motor and therefore of the pump. It has a circuit which releases a signal if the voltage generated lies below a certain threshold corresponding to the pump's minimum speed.