A firsthand account of the origins of the modern MRL
by Hongliang Liang
A technology breakthrough was announced in 1996: a way to locate a gearless permanent-magnet (PM) motor directly in the shaft to eliminate the machine room. Though the PM motor were to be small, it would produce high torque to directly drive the car and counterweight in an RPM range of one to 1,000 (versus traditional inductive-motor RPMs of one to 100). To obtain as great a driving force (torque divided by radius) as possible, the radius of the driving sheave would be as small as possible, and the ratio of the roping would be as large as possible, such as 2:1 or 4:1.