Performance and cost comparison of reluctance motors used for electric bicycles

Electric bicycles have come to be of public interest due to the awareness of energy preservation and environment. The regulations in many European countries limit the maximum electric motor power to 250 W, which assists the rider up to a bicycle velocity of 25 km/h. Due to the high market competition, electric bicycles are highly cost-sensitive. Currently, most of the electric bicycles use a brushless DC (BLDC) motor due to its compact size and high efficiency. An obvious drawback of a BLDC motor for electric bicycles is the necessity of expensive permanent magnets. Furthermore, the uncertain development of the permanent magnet price also leads to the commercial risk of the product. As a result, the motor concepts without permanent magnets could reduce significant costs and the commercial risk. This paper investigates the feasibility of reluctance motors for replacing BLDC motors in electric bicycles in terms of performances and material costs. The study focuses on two types of reluctance motors, switched reluctance motor and synchronous reluctance motor, which will be compared with a commercial benchmark BLDC motor. The considered reluctance motors will be designed to fulfill the entire torque–speed range of electric bicycles. The motor performances are calculated by design software together with simulation models using the finite element (FE) method. The material cost analysis is done based on the current market prices.