The basic principle.

A traction lift moves a car and counterweight through suspension members passing over a driven sheave. The machine controls sheave rotation while the guide system maintains the intended path.

The motor supplies or absorbs mechanical power according to load, direction and acceleration. The counterweight reduces gravitational imbalance but does not remove inertia or losses.

A controlled journey.

A worked-through example

The controller establishes the required conditions and requests movement. The drive develops torque, the brake is released in the designed sequence, and the machine moves the suspension.

Follow the relationship.

  1. ControlPlans and permits the journey.
  2. Machine and suspensionTransmit force and movement.
  3. Position feedbackSupports approach and stopping.
Conceptual relationships; arrangements vary by installation.

Connect it to the lift.

At a landing, motion control and the brake coordinate stopping and holding before the intended door sequence. Door locks, safety gear and other protective provisions remain separate functions within the complete installation.

A closer look

Gearing, roping ratio and machine location vary. The basic energy path remains useful without treating one layout as universal.

Check your understanding

Does the traction machine usually store all the ropes by winding them onto a drum?

Reveal the explanation

No. A traction sheave transfers force through contact with passing suspension members.

Further reading.

Otis: the basic workings of a lift