An AC induction motor used as the prime mover in geared elevator traction machines, operating on the principle of electromagnetic induction with a rotating magnetic field and a squirrel-cage or wound rotor.
Full Definition
Asynchronous (induction) motors dominated elevator drive systems throughout the 20th century and remain common in geared machine installations rated up to 2.5 m/s. The motor operates at a speed slightly below synchronous speed (slip of 2–8%), and torque is produced by induced currents in the rotor. Modern installations use VVVF (variable voltage variable frequency) drives to control speed and provide soft start/stop, replacing older Ward-Leonard and two-speed (Dahlander) configurations. Typical ratings for passenger elevators are 4–30 kW, IP54 enclosure, insulation class F or H. Efficiency class IE3 (premium efficiency) is mandated in EU markets under Regulation (EU) 2019/1781. Compared with PMSM (synchronous) machines, induction motors are more tolerant of drive parameter changes but less energy-efficient at partial load. Regular maintenance includes bearing inspection, winding insulation resistance testing, and cooling fan cleaning.
