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| Loss Calculation and Hot Spot Temperature Research of Rotary Electromagnetic Coupler in Wireless Charging System |
| Cheng Zhiyuan, Song Xiaoyi, WuXiaoting, Gui Zihang, Li Dongdong |
| School of Electric Power Engineering Shanghai University of Electric Power Shanghai 200090 China |
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Abstract Electromagnetic couplers are the core components of wireless power transfer (WPT), and their operating temperature determines the stability and service life of the system operation. Therefore, accurately estimating the coil winding and magnetic core losses of high-frequency electromagnetic couplers and studying the temperature rise distribution of electromagnetic couplers under normal modes are crucial for the heat dissipation design of underwater autonomous vehicles and improving the reliability of WPT systems. To address these issues, this article takes the rotary electromagnetic coupler with strong resistance to radial offset as the research object and establishes a three-dimensional electromagnetic thermal field simulation model that considers the influence of insulation induced turn spacing and temperature on material properties, achieving accurate calculation of hot spot temperature.
Firstly, theoretical analysis is conducted on the temperature rise of the electromagnetic coupler, which involves calculating the loss of the electromagnetic coupler, and then loading the loss as a heat source into the heat flow field to obtain the temperature distribution of the electromagnetic coupler; Secondly, based on the temperature rise principle of electromagnetic couplers and strictly following the temperature rise calculation process, the finite element Ansys Maxwell simulation software is used to solve the electromagnetic loss and hot spot distribution. In the simulation software, the first step is to calculate coil losses and magnetic core losses.Then, using the transient electromagnetic field heat flow field bidirectional indirect coupling method, a three-dimensional electromagnetic field simulation model is established. Finally, the electromagnetic loss calculation results are coupled as loads into the heat flux field and corresponding relationships are established to obtain the hot spot distribution of the rotating electromagnetic coupler.
The simulation results show that the magnetic field distribution of the electromagnetic coupler is basically symmetrical from top to bottom, and the magnetic field intensity gradually decreases along the center position of the magnetic core towards the end. The maximum magnetic density is located on the surface of the magnetic core close to the geometric center of the secondary coil. The average loss density distribution of the electromagnetic coupler has the same characteristics as the magnetic induction intensity distribution. At 20 ℃, the average loss errors of the primary and secondary coils within one cycle were obtained through theoretical analysis and finite element simulation, which were 2.9% and 3.4%. The experimental results show that the deviation between the parameters measured by the LCRand the numerical values in simulation is less than 10%. The thermocouple multi-channel thermometer records the temperature of the system when it reaches steady state at 20 ℃. The high-temperature area is located at the top of the secondary coil, and the deviation between the simulated temperature of the hot spot and the measured value is less than 6%, verifying the rationality of the modeling method.
The following conclusions can be drawn through experimental analysis:(1) The average loss density of the magnetic core of the rotating electromagnetic coupler is positively correlated with the distribution of magnetic induction intensity; (2) The relative position of the coil, flow velocity, and convective heat transfer coefficient all have an impact on the operating temperature of the system. At the same time, due to the influence of the nested structure, local overheating will occur under the high temperature conduction of the coil, resulting in the severe temperature rise area of the rotating electromagnetic coupling concentrated in the middle of the LCT; (3) In order to simulate the temperature rise distribution of rotary electromagnetic couplers more accurately, in addition to considering the turn spacing caused by insulation, the temperature effect of material properties should also be considered.
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Received: 17 February 2023
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2024, Vol. 39 
