A sensor system that prevents the elevator from moving when the load in the car exceeds the rated load, protecting the traction system and ensuring passenger safety.
Full Definition
EN 81-20 §14.2.5 requires that every traction elevator be equipped with an overload device that prevents departure when the car load exceeds 110 % of rated load. The device typically uses a load weighing system (strain gauge on the suspension rope hitch, floor-mounted load cell, or car frame deflection sensor) to measure car load continuously. At 80 % of rated load the device can be configured to send a 'nearly full' signal to suppress new hall calls to the car (advance notification). At ≥110 % of rated load, a buzzer activates inside the car, the door reopening device is activated to shed some passengers, and the drive circuit is inhibited — the car cannot depart until load drops below the threshold. The overload device also provides load data to the VVVF drive for torque pre-setting (load weighing compensation), improving levelling accuracy and reducing rollback on brake release.
