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The eddy current braking (ECB) is often installed on heavy-duty vehicles as the auxiliary braking component. When it works for a long time, the thermal derating of braking torque will reach about 18.5 % due to high temperature. It is important to establish an accurate magneto-thermal coupling model for the ECB high-temperature steady-state braking torque prediction. In multi-field coupling calculation, there are two commonly used data transmission methods between two physics fields. One of them is transmitting average data to important geometry based on the idea of lumped parameters (lumped parameters method), and the other is mapping the data distribution to each grid cell (direct mapping method). This paper takes the ECB as the research object, analyzes the influence of the above two data transmission methods, and proposes to replace the fluid-thermal coupling model with the heat conduction model in the magneto-thermal coupling model. Through calculation and analysis, using the lumped parameters method to transmit the heat generation rate, temperature and convective heat transfer coefficient all have a certain impact on the calculation accuracy of the coupling model comparing with the direct mapping method.

Eddy current brakes (ECB) are widely installed on heavy-duty vehicles to improve driving safety and economy. When the ECB works, the mechanical energy of the vehicle is converted into thermal energy under the action of the electromagnetic field, which is a process of mutual influence between the electromagnetic field and temperature field, and this process can be simulated by establishing a transient Magneto-thermal coupling model with bidirectional data transmission. However, due to the long calculation time required for accurate 3D electromagnetic analysis, the above model must be simplified. The parameter sensitivity analysis of the ECB shows that the temperature of the eddy current generating location directly affects the braking torque. Through the 3D electromagnetic field numerical analysis, the mapping relationship between the temperature of the eddy current generating layer and the braking torque is established and brought into the transient heat transfer model. The finite difference method is used to calculate the heat transfer model. The calculation results can predict and analyze the braking performance of the ECB during its working process.

Heavy-duty vehicles are generally equipped with non-contact hydraulic retarders or eddy current retarders to ensure safe driving during downhill conditions. The torque of the hydraulic retarder is large when the rotor rotates at a high speed, but the torque is small when the rotor rotates at a low speed. As another commonly used retarder, the eddy current retarder has a large torque at a low speed and a low power density at a high speed. High torque at full speed is the vehicles’ requirement for the auxiliary brake system, with no retarders can achieve this goal perfectly alone. Encouragingly, the braking performances of these two kinds of retarders are complementary. Based on the above properties, the eddy current-hydraulic hybrid retarder (EHR) is designed applying the principle of eddy current and the principle of hydraulic braking. In this novel HER, both sides of the rotor are used for hydraulic braking, and the outer ring of the rotor generates eddy currents. The finite element models of the flow field and the electromagnetic field are established separately and solved by computer to predict the braking torque of the EHR. The prototype was developed and the braking performance of the EHR was obtained through the bench tests. Comparing the theoretical calculation results and experimental data, the braking characteristics of the EHR are analyzed. At low speed, the EHR mainly relies on the eddy current braking, whereas at high speed, it relies on both eddy current and hydraulic braking. Moreover, the control of the EHR can be realized only by adjusting the braking torque of the eddy current part, which simplifies the control system.

Heavy-duty vehicles are generally equipped with a non- contact auxiliary brake system to ensure safe driving. As an actuator for the auxiliary brake system, liquid- cooled and embedded eddy current retarder has significant advantages in braking performance compared to the traditional eddy current retarder. The braking performance is better with the smaller gap between the stator and rotor of the retarder proved by theoretical analysis and the finite element analysis. The small gap causes conflict between the stator and rotor when the retarder works for a long time. The paper studies thermal influence on deformation of the retarder at work by establishing a multi-field coupled finite element model. And the results of the numerical simulation show that the maximum radial deformation of the stator is 0.54mm when the braking power of the retarder is 120kW. The numerical simulation results are basically consistent with the experimental results, which proves that the deformation during the continuous working of the retarder is mainly caused by thermal strain. This research provides theoretical basis and research methods for gap design between the stator and the rotor and material selection standards for high power electromagnetic products.