Development of high performance integrated drives with focus on thermals using high temperature components and additive manufacturing

The focus of this PhD is the integration of high-power electric motors with their associated power electronics to yield a high-power-density system. A primary research avenue is the computationally efficient thermal modelling of the integrated components.

In vehicle applications, both the motor and power electronic controller can produce large quantities of heat during high utilisation (known as losses) which typically requires a bespoke external cooling system to manage the temperature rise.

This presents challenges with space, and pipe routing, for liquid cooled solutions, where the motor and controller are usually on the same cooling circuit. Additional complexity and reliability issues can be found through the use of a cooling pump or forced air cooling. Furthermore, with separate controllers and motors, electrical connections, and wire routing introduces extra complexity, and potential points of failure.

Integrating the motor and controller into a single unit would allow for simplified thermal management and reduced external connections, potentially leading to improved reliability and reduced cost. A single package, integrated motor-drive would simplify installation of the powertrain into vehicles, and reduce points of failure associated with interconnects. When developing for high power systems, power electronic modularity, size of filters, electrical noise, and thermal management become larger challenges to overcome in the design.

This tightly integrated package would allow for the system to have less external connections and reduced mass through a reduction in cable and cooling tube length. This would allow for a design that's able to be more easily integrated into existing systems. With the reduced number of components and increase of standardised, mass manufacturable components, this would reduce the cost of the system allowing for a more accessible motor.

This PhD looks to improve the reliability of closely integrated control power electronics through size reduction and the use of higher temperature rated devices, utilising silicon carbide or gallium nitride. These would allow for greater space for electrical noise reduction, and improved reliability with increasing temperatures. This research is expected to have a significant practical basis, through the development of a controller circuit and mechanical housing along with design and results validation. The aim is to demonstrate a representative scale functioning prototype system on a dynamometer along with measuring the resultant efficiency and potential temperatures achieved. A comparison between a system that uses an identical motor and controller but setup in the standard configuration, where the controller is external to the motor can be made. This would allow for comparison of the efficiency with regards to the size reduction to be measured and quantified.

Thermal modelling of the heatsinking elements, optimisation of heat distribution and testing different switches for performance at higher temperatures will be performed. As the power electronics are to be mounted near the motor windings, this includes temperatures near the maximum range of the coil's insulation. Further to the design of the heatsink itself, consideration is being made for using additive manufacturing for optimising liquid coolant channels for both the motor and power electronics. Consideration is also being made for using this manufacturing method for internal electrical connections so as to reduce complexity. This project falls within the EPSRC Electrical motors and drives and electromagnetics research area.