Quantitative comparison of novel dual-PM linear motors for ropeless elevator system

Due to high land prices in the metropolitans, such as Hong Kong, Tokyo and New York, high-rise buildings are mushrooming one after another. The conventional vertical elevators in multi-level or low-rise building, which usually adopt rotational electric motors plus hoist cables with counterweights, are no longer applicable. The cable for hoisting elevators have the strength and stability problems as it gets longer and longer [1], [2]. For solving these problems, a ropeless elevator system with self-propelled cars is proposed and testified. This system adopts the linear motor to drive the elevator car and omits the counterweight and cable [3], [4]. Thus, the efficiency and operation performances are dramatically improved. Moreover, areas of the elevator hoistway can be reduced [5]. According to the requirements, linear motors for ropeless elevators need to satisfy the following features: high power density, high force density, high reliability, high ratio of payload to self-weight and low force ripple. To achieve the above features, dual permanent magnet (PM) linear motors with fault-tolerant teeth (FTT) are good candidates. When the elevator car size is fixed, one way to further increase the force density with the same current density is to adopt the dual-PM structure [6]. Thus, in this paper, four dual-PM linear motors are proposed and compared for the application of ropeless elevator system.