Thermal Management

This report provides a comprehensive overview of thermal management system strategies, modeling, and simulation within the RHODaS project. 

It focuses on detailing the thermal interface between inverters and cooling systems, exploring estimated junction temperatures, and analysing the potential impacts of design choices on equivalent thermal resistance, as well as advanced 3D thermal and power loss modeling, employing Finite Element Analysis, with COMSOL Multiphysics playing a crucial role in heatsink design. Fundamental simulations cover aspects like liquid-cooled heatsink design and sensitivity studies.

This paper presents an exhaustive review of diverse thermal management approaches at both the component and system levels, focusing on electric vehicle air conditioning systems, battery thermal management systems, and motor thermal management systems. In each subsystem, an advanced heat transfer process with phase change is recommended to dissipate the heat or directly cool the target. Moreover, the review suggested that a comprehensive integration of AC systems, battery thermal management systems, and motor thermal management systems is inevitable and is expected to maximize energy utilization efficiency.

This article reviews relevant researching work and current advances in the ever-broadening field of modern vehicle thermal management (VTM). Based on the systematic summaries of the design methods and applications of integrated thermal management (ITM), future tasks and proposals are presented. This article aims to promote innovation of ITM, strengthen the precise control and the performance predictable ability, furthermore, to enhance the level of research and development (R&D).

This article begins with a bibliographic overview of research conducted on battery thermal management systems (BTMS). The paper then analyzes lithium-ion battery types, the processes of chemical reaction, the generation of electrical energy, and the mechanisms of heat generation within the battery. In addition, the impact of temperature on thermal phenomena in batteries, including thermal runaway and lithium dendrite, is examined. The study then provides a comprehensive and critical evaluation of the thermal management strategy in recent experimental, simulation, and modeling research within the organized category of BTMS for all-electric and hybrid vehicle battery packs.

This document reports on the laboratory testing of the Thermal Management System (TMS) for a 150 kW High-Power Converter (HPC). Two prototype heatsinks, one made of copper and the other of aluminium, were tested. The aluminium heatsinks showed significant weight reduction while maintaining heat dissipation efficiency. The TMS is integral to the RHODAS project's 150 kW Integrated Motor Drive (IMD), ensuring optimal temperature for power converters in electric vehicles. The TMS, including the aluminium heatsink module, radiator, fan system, coolant pump, and piping, demonstrated effective performance under various thermal loads in laboratory conditions.
 

Supported by Computer Aided Engineering (CAE) and Computational Fluid Dynamics (CFD) analyses, the TMS design proved to be robust and scalable. Test results will guide future optimizations to enhance thermal efficiency and system integration for vehicle applications. The TMS is critical in preventing overheating, improving reliability, and extending the lifespan of components in electric vehicles (EVs).

In recent years, semiconductor manufacturers have developed power component packages which use a different thermal management approach - instead of placing the thermal pad on the bottom of a device pointing towards the PCB, the exposed metal pad is placed on the top side of the device. It has been shown that top-side cooling (TSC) can reduce the overall thermal resistance by 20% - 30% compared to bottom side cooling (BSC), making the process of heat extraction much simpler and consequently less expensive to implement. Ideas & Motion, a company which develops power inverters for electric vehicle (EV) powertrains, conducted simulations as part of the HiPE EU-funded project to assess the thermal performance of TSC packages from three leading semiconductor manufacturers.

The switching-cell array is a flexible device formed by a matrix arrangement of highly optimized switching cells all at the same voltage rating. The switching cells within a switching-cell array can be interconnected in different ways, providing some degrees of freedom that could be exploited to pursue reduction and/or more even distribution of power losses in the power converters. To compare power converter legs based on different configurations of switching-cell arrays, a proper steady-state average thermo-electrical model is required, to estimate losses and temperature of all power semiconductor devices within the converter legs. This work presents the thermal analysis of power devices within power converter legs based on switching-cell arrays. Detailed transient and steadystate average thermo-electrical models are provided to calculate the conduction and switching losses, together with the junction temperature of the power devices. The steady-state average thermo-electrical model operates faster than the transient model, with comparable accuracy to the transient model. The accuracy of the steady-state average model is evaluated by comparison to the transient model, under different scenarios and through analytical studies. Finally, both thermo-electrical models are verified through experimental tests.

Hairpin windings are often applied in propulsion motors of electrical vehicles. There are several reasons supporting the technology. In mass production, hairpin winding work can be effectively automated, rectangular conductors offer a high copper space factor, a relatively simple structure and improved thermal management capability. However, due to additional AC losses generated at higher operating speed, there is a risk of local hot spots within the stator slot region, which might lead to overheating risk and insulation damage. There is also a growing interest to produce higher and higher specific power machines. Therefore, a new cooling concept is proposed that further improves the thermal management of the hairpin winding and allows to increase the specific power of the machine. The proposed method is based on direct oil cooling (DOC) through the channel of the hollow conductor. Special inlets and outlets in each hairpin coil are arranged. Comparison of the proposed cooling arrangement with the traditional cooling of machine with hairpin winding is provided by applying finite element method (FEM).