A control function or mechanical device that prevents the elevator car from rolling backward against the intended direction of travel at start-up.
Full Definition
Rollback (or roll-back) occurs when the electromagnetic brake releases but the motor has not yet developed sufficient torque to hold the load, causing the car to briefly slide in the direction of gravity. This is particularly hazardous in heavy-load or downward-travel starts. Anti-rollback is achieved through coordinated brake-release and motor torque control in the VVVF drive — the load weighing device pre-charges the motor with the correct torque value before brake release, eliminating rollback. Mechanical anti-rollback ratchets are used in rack-and-pinion elevators. EN 81-20 mandates that the car shall not move in the unintended direction at start.
