Axial flux permanent magnet motors are widely used in fields with high requirements for motor performance and installation space due to their advantages of high power density and small size, but the AC copper consumption of flat copper wire of axial flux permanent magnet motors will seriously affect the performance of the motor. The research team of Shenyang University of Technology proposed a hybrid analytical calculation method for AC copper consumption of flat copper wires, and proposed to use the conductor arrangement of flat wires to suppress AC copper loss. Finally, a 60kW prototype was fabricated, and the accuracy of the research content was verified through prototype experiments.
Background:
Compared with traditional radial flux permanent magnet motors, axial flux permanent magnet motors have the advantages of higher power density, smaller volume and lighter weight, and are suitable for fields with high requirements for motor performance and installation space, such as aerospace, renewable energy, electric vehicles, etc.
The electromagnetic load and thermal load of high power density axial flux permanent magnet motor tend to the limit, and are affected by skin effect, proximity effect and external magnetic field, resulting in large AC copper consumption and high temperature rise in the winding, which will seriously affect the performance of the motor and the life of the insulating material. Moreover, in the field of high power density motors, flat copper wire is used because of its high slot filling rate and excellent heat dissipation performance, but flat copper wire has higher AC copper consumption. Therefore, it is necessary to accurately calculate and suppress the AC copper consumption of flat copper wires.
The problem solved by the paper and its significance
Although accurate results can be obtained by using 3D transient fields to calculate AC copper consumption, there are problems such as long calculation time and high requirements for computer performance. The hybrid analytic calculation method proposed by the team balances the calculation accuracy and calculation time. Moreover, the AC copper consumption of flat copper wire is large, which will seriously affect the performance of the motor. The team proposed a conductor arrangement with flat wires winding to suppress AC copper loss. It provides a reference for quickly and accurately calculating the AC copper consumption of flat copper wires, and also provides a basis for optimizing the design of high power density motors.
Dissertation Methods and Innovations
(1) Mixed analytical calculation
In this paper, a hybrid analytical calculation method is proposed, which can consider the effects of skin effect, proximity effect and external magnetic field on the AC copper loss of flat copper wires. This method combines the three-dimensional finite element and the analytical method, and uses the analytical formula to calculate the AC copper consumption of the flat copper wire based on the magnetic flux density calculated by the finite element.
Fig.1. Magnetic flux density sampling
(2) Conductor arrangement and simulation analysis
In this paper, the AC copper loss of different conductor arrangements is compared, and the conductor arrangement of flat wire vertical winding is proposed to suppress the AC copper loss.
Fig.2. Detailed model of vertical winding of flat wire
Fig.3. AC copper consumption of flat wire vertical winding conductor
(3) Experimental verification
In this paper, a prototype machine was fabricated, and the wire type of the winding was flat copper wire, and the conductor arrangement of flat wire vertical winding was adopted. The structure and prototype of the flat copper wire are shown in Figure 4, and the experimental platform of the prototype is shown in Figure 5. The relationship between phase current and efficiency at 2500r/min is shown in Figure 6, and the experimental results, the three-dimensional finite element simulation results and the mixed analytical calculation results are basically in good agreement, which proves that the accuracy of the mixed analytical calculation and the effectiveness of the flat wire vertical winding are basically consistent.
Fig.4. Winding structure and prototype
Fig.5 Motor test platform
Figure 6 Efficiency comparison
conclusion
In this paper, the three-dimensional finite element and analytical method are combined to propose a hybrid analytical calculation method that can consider the effects of skin effect, proximity effect and external magnetic field on the AC copper loss of flat copper wires. The method used to calculate the AC copper consumption has the advantages of high calculation accuracy and short calculation time, and is also suitable for quickly analyzing the influence of different flat copper wire arrangement on the AC copper consumption. At the same time, the conductor arrangement of flat wire vertical winding is proposed, which can effectively suppress AC copper loss. Under the rated operating conditions, the AC copper consumption of the flat wire vertical wound is reduced by 36.9%, and the difference becomes more and more obvious as the frequency increases.
Meet the team
The research team of Shenyang University of Technology has long been committed to the design of high-power density axial flux motors for electric aviation, modern motor control technology, multiphase motor control methods, electric vehicle electric drive control systems, robot joint servo motors and their control technologies, etc., and the team has published more than 20 papers in important journals at home and abroad, and authorized more than 10 invention patents.
Zhifeng Zhang, Professor, Doctoral Supervisor, research direction of electric aviation high power density axial flux motor, electric vehicle electric drive system, domain controller, dual three-phase permanent magnet synchronous motor control method, robot joint servo motor and its control technology, etc.
Yue Wu, Ph.D., specializes in the design, control and multi-physics analysis of axial flux permanent magnet motors.
Sun Quanzeng, Ph.D. candidate, research direction is multiphase permanent magnet synchronous motor control.
The results of this work were published in the 24th issue of Transactions of China Electrotechnical Society in 2023, and the title of the paper is "Mixed analytical calculation and suppression of AC copper loss in flat copper wire of axial flux permanent magnet motor". This project was supported by the National Natural Science Foundation of China and the Liaoning Provincial Department of Education.