There are two primary classes of electric elevator: the geared traction motor elevator and the gear less traction motor elevator. Geared traction motor elevators are driven by vector motors coupled to gearboxes. The gearing, in turn, drives the traction wheels or sheaves, which are grooved pulleys that move the cables that raise and lower the car. Although geared traction motor elevators are reliable, the bulky equipment must be housed in a machine room. That adds cost and occupies space.
Gear less traction motor elevators take a different approach. Instead of a vector motor/gearbox combination, they use permanent-magnet DC motors coupled directly to the load. The motors tend to be larger in diameter but narrower. This pancake form factor enables them to be placed either above the elevator in the hoist way, eliminating the need for a machine room.
Space Elevators motor elevators use motor encoders to monitor speed and position, as well as to commutate the motor. Although absolute encoders are often used for commutation, incremental elevator encoders exist targeted specifically for elevator applications.
