Comparative Analysis of Thermal Calculation Methods for Permanent Magnet Motors with Fan Cooling
In order to compare and analyze the feasibility of different thermal calculation methods in motor thermal design and engineering application, this paper takes a self-fan air-cooled permanent magnet motor as the research object, and analyzes its fan working flow, motor fluid field and motor temperature rise. The analytical working method and the finite volume method are used to calculate the rated working air volume of the motor fan, and the velocity distribution of the whole fluid domain of the motor is obtained by the finite volume method. Based on the fluid calculation, the equivalent thermal path method and the finite volume method are used respectively. Temperature rise is estimated. By comparing the calculated values with the measured values, the two methods have certain credibility. The finite volume method is more suitable for the design improvement and optimization of the motor. The analytical method can be used for the design of the derivative motor and the preliminary evaluation of the program.
With the development of economy and society, low-carbon environmental protection and high-efficiency energy conservation have become the focus of attention in all walks of life. Among them, rare earth permanent magnet motors have received extensive attention and application due to their simple structure, small size, light weight and high efficiency. 2]. In the field of rail transit, in order to effectively protect the permanent magnets, the permanent magnet motor generally adopts a fully enclosed structure, which leads to poor heat dissipation environment of the motor; in addition, the increase of the power density of the motor causes the loss of the unit volume generated by the motor during operation, which will aggravate the motor. The temperature of each part is increased. Higher temperatures can cause serious damage to the safe operation of the motor once the permanent magnet is irreversibly demagnetized. As the core component of rail transit vehicles, the accurate calculation and estimation of the internal temperature field of the motor lays a solid foundation for ensuring the safe operation of the motor, saving design cost and shortening the development cycle. The motor thermal design methods mainly include simplified formula method, equivalent thermal path method, thermal network method and numerical calculation method. These methods have advantages and disadvantages in terms of calculation accuracy and design cycle.
In order to study the feasibility and effectiveness of different calculation methods in motor thermal design and practical engineering applications, this paper takes a self-contained fan-cooled fully enclosed permanent magnet synchronous traction motor as the research object, and compares the thermal design methods of the motor. . In this paper, the analytic method and the simulation calculation method are used to calculate and compare the temperature rise of the motor. Firstly, the motor fan and its flow channel are analytically calculated and simulated by the three-dimensional fluid field, so that the fan can be produced under the rated working condition. The air volume is then calculated and analyzed based on the fluid field calculation results by the thermal path method and the finite volume method [7-9]. The permanent magnet motor rotor basically does not generate heat, and the analytical method based on the equivalent two heat source thermal path is adopted. The calculation method is simple, and the temperature rise of the stator winding can be quickly estimated. It is preliminarily judged whether the electromagnetic scheme design of the motor is reasonable; based on the simulation calculation of the finite volume method, It can analyze and evaluate the global fluid field and temperature field of the motor, which is more conducive to the improvement and optimization of the motor scheme.
