Glossary
Machine-Room-Less (MRL)
A traction elevator design that places the motor, drive, and controller inside the hoistway or on an adjacent wall, eliminating the need for a dedicated machine room above or beside the shaft.
Machine-room-less elevators were introduced commercially in the mid-1990s and have since become the dominant type for new traction installations in low- to mid-rise buildings. The key enabling technology is the permanent-magnet synchronous motor (PMSM), which is compact enough — typically 40–60 cm in diameter and 15–25 cm thick — to mount on a bracket inside the hoistway, usually at the top of the shaft on the guide rail structure.
The controller and VVVF drive are housed in a wall-mounted cabinet accessible from the top landing, so technicians can service the electronics without entering the hoistway. MRL systems typically use 2:1 roping to allow a smaller motor to achieve adequate car speed, and they achieve energy efficiency comparable to or better than traditional geared traction machines.
The primary advantage of MRL is space savings. Eliminating the machine room frees 10–15 square metres of floor space that the building owner can use or sell. It also simplifies construction and can reduce building height. MRL systems handle rises up to about 100 metres and speeds up to about 4 m/s, making them suitable for the majority of buildings up to approximately 30 storeys.