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To solve theproblems of an insufficient braking moment for the eddy current retarder at high speed, a small braking moment and slow response of the hydraulic retarder at low speed, and a low power density of the existing electromagnetic hydraulic retarder(EHR), a novel radially distributed electromagnetic-hydraulic retarder(R-EHR) was proposed. The R-EHR fully absorbs the advantages of the braking characteristics of hydraulic retarders and eddy current retarders. The cooling fluid is used to realize the braking of the hydraulic part. At the same time, it acts on the heating surfaces to improve the torque of the electromagnetic part. In this paper, finite element models of the flow field and electromagnetic field are established to predict braking performance. The braking performance of the R-EHR is obtained by bench test, the error between the simulation and experimental data is compared, and the experimental data are analyzed. The results show that the proportion of electromagnetic braking torque in the novel R-EHR is more reasonable. The braking torque increased by 26% and the power density increased by 37.5% at 2000 RPM compared to that of the EHR. The R-EHR can control the braking torque only by adjusting the current, thus simplifying the control system. [ABSTRACT FROM AUTHOR]

In this article, a clear analytical model for predicting the performance of permanent magnet (PM) eddy current couplers is proposed. The interaction of the reaction magnetic fields between adjacent eddy current rings was considered for the first time. Based on a magnetic equivalent circuit (MEC) and the Ampere circuital theorem, the accurate distribution of the air gap magnetic field under different slip velocities was deduced in a 2-D model, and the analytical expression of the transmission torque was obtained. 3-D effects were also taken into account to calibrate the model. The validity of the analytical model was verified by comparison with results from the 3-D finite element method (FEM). The comparison shows that the analytical model can accurately predict the magnetic field distribution and transmission torque over a wide range of slip velocity variations. This model can greatly reduce the number of calculations required and save time, and it is suitable for the preliminary design and optimization of PM eddy current couplers. [ABSTRACT FROM AUTHOR]

As an auxiliary brake element, the eddy current brake is widely used to ensure safe driving in heavy vehicles due to its noncontact braking characteristics. It is important to increase the power density of the eddy current brake and suppress the thermal derating of its braking performance. According to the principle of the eddy current braking and current skin effect, a decline in temperature can greatly increase the eddy current density of the low-frequency electromagnetic device. In this paper, a new heat dissipation method is proposed to cool the heating surface of the eddy current brake directly. The electromagnetic field model and the flow-heat coupling model are established to predict and analyze the steady-state temperature distribution and braking torque. A new type of internal liquid cooling eddy current brake prototype was manufactured for a bench test. The experimental data prove that the computational model is effective. The calculation results show that the new internal liquid cooling eddy current brake has improved heat dissipation advantages. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Braking torque is the most important performance parameter for a permanent magnet retarder used in heavy vehicles. This paper proposes a model of the permanent magnet retarder for braking torque at different speeds considering the skin effect, the magnetic leakage, and the actual path of the eddy currents. Based on the magnetic equivalent circuit and the piecewise function method, the static and the transient air-gap flux density models are established, and their accuracy is verified by comparison to the finite element method (FEM). The permeability distribution curve of the retarder stator is obtained by a simple permeability-measuring instrument, considering the skin effect on the permeability of the stator. Thus, the effective permeability function of the stator is obtained at different rotational speeds, and the transient air-gap flux density model is optimized using the effective permeability function. The simulation results showed that the optimized transient air-gap flux density of the calculation model was in good agreement with the FEM. Finally, the calculation model of the eddy current braking torque was verified by the bench test. [ABSTRACT FROM AUTHOR]

Aiming at the heat fade of the continuous braking and low power density of traditional eddy current retarder (ECR) for heavy vehicles, a new liquid-cooled and flywheel-type eddy current retarder is proposed. The new ECR can keep a low working temperature because of the cooling type. It is assembled between the engine and the clutch, which can effectively improve the braking power density. The transient electromagnetic field of the ECR is solved by the finite-element method, and the braking torque characteristic curve is obtained. The thermal-fluid coupling field is analyzed using the computational fluid dynamics method. Finally, the structure parameters optimization of the rotor tooth is carried out. The braking torque increases by 14.8% and the weight of rotor tooth decreases by 9.5% after optimization. The test results show that the heat fade ratio of the new ECR braking torque is only 8.6%, but that of the traditional ECR is 46.7%. [ABSTRACT FROM AUTHOR]

To both overcome the serious thermal recession problem and conserve energy for conventional eddy-current brakes, a self-excited and liquid-cooled electromagnetic retarder (SL-EMR) assembly is proposed. The design includes a stator with an internally cooled channel, a rotor with multiple magnetic heads, and an integrated generator without brushes. The assembly and operating principles are analyzed. Models of the braking and generating systems are established. The electromagnetic field model analysis, braking performance analysis, thermal field analysis, and generator characteristic analysis of the SL-EMR are simulated using the finite-element method (FEM). The SL-EMR performance is bench tested, and the results show a 6% difference between the FEM results and the experimental results. The integrated generator provides adequate exciting current for the braking system. The braking torque decreases by only 10.4% during continuous braking conditions. The braking torque reached 2000 \N\cdot \m when the speed was 1500 r/min and the coil current was 30 A. [ABSTRACT FROM PUBLISHER]

To overcome the serious thermal recession problem that has been associated with the braking torque of conventional eddy current brakes, and to conserve energy, this paper has proposed a novel self-excited eddy current retarder (S-ECR). The design includes a stator with an internally cooled channel, a rotor with double salient poles, and a built-in generator. The electromagnetic field analysis and the performance analysis of the S-ECR were carried out using the finite-element method. The S-ECR performance was tested at a test bench. The test results showed that the calculated braking torque and the generator performance were in reasonable agreement with the measured results. The braking performance did not obviously diminish during the continuous braking stage. When the speed was 1500 r/min and the exciting current was 30 A, the braking torque could reach 1600 N·m. [ABSTRACT FROM AUTHOR]

A liquid-cooled eddy current retarder (ECR) with a dual salient poles design is proposed in this paper. Finite element models were developed to perform transient magnetic analysis and steady-state conjugate heat transfer analysis. The braking torque, eddy current field and thermal field of the retarder were each predicted. The retarder was subjected to two sets of tests on a test bench, to obtain the braking torque at various rotational speeds, while utilizing two different magnetomotive forces, respectively, and the torque was also tested while maintaining a constant rotational speed, for a specific amount of time. The good agreement shown between the calculations and measured data of the braking torque served to validate the analysis method. The experiments also showed that the braking torque of the retarder decreased more slowly than the braking torque of conventional ECRs in continuous operation. [ABSTRACT FROM AUTHOR]

This paper proposes a novel permanent magnet retarder (PMR) structure that uses water cooling to improve the braking performance of conventional PMR for heavy vehicles. A finite element model for a water-cooled PMR was developed by considering the temperature dependence of magnetic characteristics and heat conductivity. The eddy current and temperature distribution were analyzed using the magneto-thermal coupled method. Retarder performance was tested at a test bench. The test results show that the calculated temperature and braking torque agreed fairly well with the measured results. PMRs can maintain a low working temperature by using water cooling. Compared with air-cooled retarder, this retarder's braking torque does not decrease much under continuous working conditions. [ABSTRACT FROM PUBLISHER]