Sensorless Safety Standstill Monitor
2-channel standstill monitoring of motors
The new DOLD safety standstill monitor LH5946 detects standstill of disconnected motors independent of the rotating direction. It fulfils SIL 3 and PL e/SK 4 and is used to release a solenoid locking switch or to activate a mechanical hold in brake, e.g. on woodworking machines, machine tools or on conveyor systems. This provides fast access to dangerous areas of a plant for service and maintenance.
Proximity sensors and speed sensors are not necessary. This saves cost, installation work and allows efficient refurbishment. The unit measures the back emf voltage of a freewheeling motor. The unit is connected directly to the motor supply wires. Residual voltage on the measuring circuit up to some volts, can be compensated by adjusting the response value.
The unit includes extended failure diagnosis and is often used with frequency inverters.