CET Traction Elevator Mechanics 3

Question 1

What is the significance of the 'T1/T2 ratio' in traction elevator design?

Accepted Answer

It is the ratio of rope tension on the load side to the slack side, determining traction capacity

Answer

The T1/T2 ratio compares the heavy (load) side tension to the light (counterweight) side tension and must not exceed the traction capacity of the sheave-rope system.

Question 2

Undercut grooves on a traction sheave are used primarily to:

Accepted Answer

Increase traction by raising the effective friction coefficient

Answer

Undercut grooves create a higher contact pressure on the rope sides rather than the bottom, effectively increasing the traction coefficient.

Question 3

What happens to traction if a traction elevator hoist rope becomes oil-contaminated?

Accepted Answer

Traction decreases, risking rope slippage on the sheave

Answer

Oil contamination significantly reduces the friction coefficient between the rope and sheave groove, diminishing traction capacity.

Question 4

In a gearless traction machine, what directly drives the sheave?

Accepted Answer

The motor rotor shaft without intermediate gearing

Answer

Gearless machines connect the sheave directly to a slow-speed, high-torque motor, eliminating gearbox losses and noise.

Question 5

What type of motor is most commonly used in modern gearless traction elevator machines?

Accepted Answer

Permanent magnet synchronous motor (PMSM)

Answer

Permanent magnet synchronous motors are favored in modern gearless machines for their high efficiency, compact size, and precise speed control.

(CET) Certified Elevator Technician Practice Test

(CET) Certified Elevator Technician Practice Test

CET Traction Elevator Mechanics 3