The complete set of interacting safety systems — governor, safety gear, brake, and drive electronic monitoring — that detect and respond to uncontrolled car acceleration or descent above the rated speed.
Full Definition
Elevator overspeed protection is a layered defence-in-depth system described in EN 81-20 §5.6 and §5.9. The layers operate in sequence as speed increases beyond rated: Layer 1 — Drive electronic overspeed monitoring: VFD encoder-based speed monitoring inhibits the drive and applies the machine brake when speed exceeds typically 110 % contract speed; Layer 2 — Overspeed governor electrical trip: centrifugal governor switch opens the safety circuit at ≥ 115 % contract speed (EN 81-20 §5.6.2), cutting power to the brake coils; Layer 3 — Overspeed governor mechanical trip: governor jaws grip the governor rope, mechanically actuating the progressive safety gear on the car sling; Layer 4 — Progressive safety gear (Parachute): wedge or roller jaws clamp onto the guide rails, decelerating the car within EN 81-20 §5.6.7 retardation limits (0.2–1.0 g). On the counterweight side, a counterweight safety device may also be required per EN 81-20 §5.6.5. All components forming the overspeed protection chain must be type-examined per EN 81-50 and individually serialised in the technical file. Testing at commissioning requires a governor rope pull test and, where practicable, a full-speed drop test with rated load.
