Outer-rotor Permanent-magnet Motor Research Articles

Cooling structure design for an outer-rotor permanent magnet motor based on phase change material

• A cooling structure of an outer-rotor PM motor based on PCM is proposed. • The structure can prolong the operating time by 149 s under 2 times overload. • The thermal conductivity of PCM is enhanced by porous copper foam. • The composite PCM prolongs the operating time by 16.8% compared with pure PCM. For a small-sized outer-rotor permanent magnet (PM) motor during overload operation, the internal heat increases sharply and the effective heat dissipation area is seriously insufficient. Aiming at the heat dissipation for the motor, given the limitation of size, a passive cooling structure based on phase change material (PCM) is proposed in this paper. The copper shell filled with PCM is mounted between the flange and end winding using the thermally conductive silicone. The three-dimensional model of the PM motor and the cooling structure is established and the heat dissipation is simulated by finite element method. The experiment is conducted and the results show that the cooling structure can prolong the operating time of the motor by 149 s under 2 times overload. Additionally, the PCM-copper foam composite consisted of PCM and porous copper foam is adopted to enhance the thermal conductivity. The experimental results show that the operating time of the motor is prolonged by 16.8% compared with pure PCM, and the overload capability is enhanced.

Rheometer-Based Cogging and Hysteresis Torque and Iron Loss Determination of Sub-Fractional Horsepower Motors

Accurately measuring the cogging torque, hysteresis torque, and iron losses of permanent magnet (PM) motors is a challenging task. This is especially true for sub-fractional horsepower (SFHP) variants used, e.g., in auxiliary drives for automotive fan and pump applications. Their cogging torque and hysteresis torque peak values are often in the sub-milli-Newton meter range, causing conventional measuring methods and devices to fail as especially friction impedes the measurement significantly. Moreover, their iron losses are hard to determine and usually merely estimated in the literature. This article presents an unconventional rheometer-based method to determine both 1) the cogging torque and hysteresis torque of SFHP PM motors and 2) their iron losses by evaluating the observed offset torque. Two SFHP outer-rotor PM motor topologies for fan applications are analyzed, i.e., a claw-pole motor and a salient-pole motor. The results show that, with the proposed setup, settings, and evaluation, a rheometer can successfully be used to determine the cogging torque and hysteresis torque waveforms in the sub-milli-Newton meter range and the iron losses of SFHP motors, both with excellent accuracy.

Torque Ripple Minimization and Performance Investigation of an In-Wheel Permanent Magnet Motor

Recently, electric vehicle motoring has become a topic of interest, due to the several problems caused by thermal engines such as pollution and high oil prices. Thus, electric motors are increasingly applied in vehicle’ applications and relevant research about these motors and their applications has been performed. Of particular interest are the improvements regarding torque production capability, the minimization of torque ripple and iron losses. The present work deals with the optimum design and the performance investigation of an outer rotor permanent magnet motor for in-wheel electric vehicle application. At first, and in order to find the optimum motor design, a new based particle-swarm multi-objective optimization procedure is applied. Three objective functions are used: efficiency maximization, weight and ripple torque minimization. Secondly, the effects of the permanent magnets segmentation, the stator slots opening, and the separation of adjacent magnets by air are outlined. The aim of the paper is the design of a topology with smooth output torque, low ripple torque, low iron losses and mechanical robustness.

High Precision Control System Design and Implementation of Outer-Rotor Permanent Magnet Motor with Dual Magnetic Sensors

The paper propose an outer-rotor permanent magnet synchronous motor (PMSM) with peak torque of 3000N.m. The position measuring system based on CPLD and dual magnetic sensor is developed. This system can handle two channel signals obtained from two sensor heads, and provides correct and reliable position feedback signals for the motor control. According to the mathematical model of the PMSM, full digital high precision control system with triple feedback closed loops are designed and implemented in experimental evaluation. The test results validate that the system is feasible and the control precision can reach 1.5 arc-second.

A high torque density permanent magnet motor for oil pumping unit

A low speed, high torque density compound permanent magnet (PM) motor is developed for oil pumping unit to reduce energy consumption. It consists of dual axial-field PM motors and an outer rotor PM motor. In order to account for the influence of skew, a multislice two-dimensional finite element method is employed to analyze the air gap field distribution, back-emf, cogging torque, and electromagnetic torque. Predicted results are validated experimentally.