Riassunto analitico
Electrification plays a crucial role in transportation decarbonisation. However, electric machines still pose environmental challenges, primarily due to the materials used, such as copper and rare earth elements. Effective thermal management of traction electric machines is a key strategy to minimize the reliance on these environmentally impactful materials. This work focuses on designing a cooling system for a heavy-duty application, exploring various solutions implemented in benchmark systems and selecting the most suitable one. In the first part of this thesis, the most promising cooling systems are reviewed and analyzed. Then, considering the electromagnetic design of an Interior Permanent Magnet (IPM) machine and the related losses, the best solution is chosen in terms of required knowledge, simplicity, and effectiveness. In this study, the motor is equipped with a properly designed cooling jacket, developed using a DoE approach to explore different parameter combinations. To enhance heat transfer in critical hot spot areas, potting material was added between the end windings and the housing. Based on the state-of-the-art analysis, the most common cooling jacket designs feature helical coils with rectangular or cylindrical channels or axial coils with rectangular channels. The comparison between the different solutions is based on the capability of extracting the same amount of heat and evaluating the pressure drop inside the channels. This is done to maximize the overall efficiency of the machine. To be able to evaluate the best one, analytical calculations have been done to do a first screening. Afterwards, to save time, only the chosen solutions are simulated and validated. In order to verify the results obtained, a CFD simulation is performed, considering only the fluid. After having run the simulation, the results confirm what was analytically computed, and so the final design has been confirmed. Afterwards, since the motor has twelve poles, only one pole of the electric motor has been simulated to verify the thermal behavior. To set the simulation, the selected slice of the motor is modeled and simulated to verify the effectiveness of the chosen system. To ensure that material temperatures remain within the safety threshold, two steady-state thermal simulations are conducted under the worst operating conditions which are at base speed and at high velocity, both at nominal torque. The transient behavior of the motor has been verified using the heavy-duty diesel truck cycle (HDDTC). Once the capability to run the HDDTC has been ensured, also a wide open throttle situation, considering 30 seconds of overload capability, is performed. In this way, the overall design of the cooling jacket has been validated.
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Abstract
Electrification plays a crucial role in transportation decarbonisation. However, electric machines still pose environmental challenges, primarily due to the materials used, such as copper and rare earth elements. Effective thermal management of traction electric machines is a key strategy to minimize the reliance on these environmentally impactful materials. This work focuses on designing a cooling system for a heavy-duty application, exploring various solutions implemented in benchmark systems and selecting the most suitable one. In the first part of this thesis, the most promising cooling systems are reviewed and analyzed. Then, considering the electromagnetic design of an Interior Permanent Magnet (IPM) machine and the related losses, the best solution is chosen in terms of required knowledge, simplicity, and effectiveness. In this study, the motor is equipped with a properly designed cooling jacket, developed using a DoE approach to explore different parameter combinations. To enhance heat transfer in critical hot spot areas, potting material was added between the end windings and the housing. Based on the state-of-the-art analysis, the most common cooling jacket designs feature helical coils with rectangular or cylindrical channels or axial coils with rectangular channels. The comparison between the different solutions is based on the capability of extracting the same amount of heat and evaluating the pressure drop inside the channels. This is done to maximize the overall efficiency of the machine. To be able to evaluate the best one, analytical calculations have been done to do a first screening. Afterwards, to save time, only the chosen solutions are simulated and validated. In order to verify the results obtained, a CFD simulation is performed, considering only the fluid. After having run the simulation, the results confirm what was analytically computed, and so the final design has been confirmed. Afterwards, since the motor has twelve poles, only one pole of the electric motor has been simulated to verify the thermal behavior. To set the simulation, the selected slice of the motor is modeled and simulated to verify the effectiveness of the chosen system. To ensure that material temperatures remain within the safety threshold, two steady-state thermal simulations are conducted under the worst operating conditions which are at base speed and at high velocity, both at nominal torque. The transient behavior of the motor has been verified using the heavy-duty diesel truck cycle (HDDTC). Once the capability to run the HDDTC has been ensured, also a wide open throttle situation, considering 30 seconds of overload capability, is performed. In this way, the overall design of the cooling jacket has been validated.
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