CET Machine Room & Pit Equipment Flashcards

What is the purpose of the motor brake on a geared traction elevator?

Answer: Holds the car stationary when the motor is de-energized

The motor brake is a spring-set, electrically released device that holds the sheave and car stationary whenever the drive motor is not powered.

What is the maximum allowable wire rope (hoist rope) diameter used in most standard traction elevator installations?

Answer: 5/8 inch

Most standard traction elevator installations use hoist ropes up to 5/8 inch (16 mm) in diameter, though actual size depends on the design load.

In a machine room, what is the purpose of the 'selector' or 'dispatching system'?

Answer: Tracks car position and manages hall and car calls

The selector is a position-tracking and dispatching system that monitors car location and manages the queue of hall and car calls for efficient service.

What is the function of the deflector sheave in a machine room or overhead?

Answer: Changes the direction of the hoist ropes between the drive sheave and the car or counterweight

A deflector sheave redirects the hoist ropes to properly align them between the drive sheave and the car or counterweight connection points.

What safety device prevents an elevator from operating with the machine room access door open?

Answer: Machine room door interlock

A machine room door interlock (access switch) de-energizes or restricts elevator operation whenever the machine room door is opened, protecting personnel.

What is the purpose of the phase reversal relay in an elevator machine room?

Answer: Prevents operation if incoming power phases are reversed or missing

A phase reversal relay monitors the three-phase power supply and prevents the elevator from operating if phases are reversed or a phase is lost, which would cause the motor to run backward.