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Welcome to Classroom on demand, your source for educational materials related to the vertical transportation industry. This site represents the knowledge and expertise of the best engineers and mechanics in the elevator industry, and will help those new to the elevator industry learn about the basic workings of elevator systems, and also will serve as a reference for people with more experience.

Governor Module

The governor, which is located in the machine room or overhead depending on the elevator design, is a speed monitoring device on traction elevators that triggers the safety mounted on the car frame when the elevator over-speeds in either direction. The governor rope runs over the governor sheave and down to the elevator car and is attached to the safety trip mechanism. The governor rope continues to the pit and runs over a pit mounted sheave and turns back to the governor sheave located in the machine room or overhead. This governor rope arrangement forms a continuous loop while the elevator moves up and down the hoistway.

If an elevator over speeds either because of a mechanical malfunction or the suspension ropes are severed then the governor sheave accelerates as the car accelerates until a preset speed limit is attained and a speed sensing device is tripped. At that point the governor’s rope griping jaw is activated to seize the governor rope. As the car continues to descend, the stopped governor rope moves the fixed car safety operating lever to engage the safety jaws installed at the ends of the safety plank. The safety jaws normally slide along the two main rails until the safety is “set” by the governor. Once the safety is set the safety jaws grip the guide rails. Friction between the safety jaws and the guide rails slow the car to a halt.

If an elevator car is traveling at a rated speed of 350 fpm (1.7 fpm) an a malfunction develops the governor will set the safety jaws at a speed of 400 fpm (2.03 m/s)(4.55 mph). Once the safety jaws engage the rails the car will be brought to a halt in about 6.5 inches.

An elevator can also over-speed in the up direction. With a 40% counterweight and an empty or lightly loaded elevator the elevator car would be pulled in the up direction while the counterweight, in this situation, would be the heaver mass and move in the down direction. The governor would sense the over speed condition and set the safety which would stop the upward traveling elevator.

In addition to triggering the safety, when a governor’s over speed switch is tripped it activates the car safety devices, cutting the power to the drive, and initiating the brakes, if necessary.

The governor is usually encoder capable. Mounted on the governor, the encoder tracks the precise location of the elevator and relays the information back to the controller.

Tags:  traction Safety


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