Traction

Traction elevators are what most people think of when they think of an elevator. The elevator cab and a counterweight are suspended by specially designed steel hoist ropes that run over a sheave with grooves designed to grab the ropes. Their name is derived from the traction between the hoist ropes and the traction sheave.

There are essentially only two configurations for traction elevators; overhead and basement. Each of these configurations rely upon a motor that turns the traction sheave and thus transmits the motion to the elevator. Both alternating current and direct current motors are used in traction elevators. The speed of the elevator is regulated by the type of control system.

Currently, typical speed control of a traction elevator is accomplished by either variable voltage in direct current applications and variable voltage variable frequency in alternating current applications. Earlier alternating current control systems were single and two-speed control systems. Due to inaccurate floor stop performance and the associated liability, these types of control systems have fallen in popularity.