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Details of Grant 

EPSRC Reference: EP/T017988/1
Title: Advanced Thermomagnetic Cooling for Ultrahigh Power Density Electrical Machines
Principal Investigator: Li, Professor G
Other Investigators:
Morley, Professor NA Zhu, Professor Z
Researcher Co-Investigators:
Project Partners:
Motor Design Ltd Safran SA / Safran Tech
Department: Electronic and Electrical Engineering
Organisation: University of Sheffield
Scheme: Standard Research
Starts: 01 September 2020 Ends: 31 May 2023 Value (£): 461,859
EPSRC Research Topic Classifications:
Electric Motor & Drive Systems
EPSRC Industrial Sector Classifications:
Transport Systems and Vehicles
Related Grants:
Panel History:
Panel DatePanel NameOutcome
03 Dec 2019 Engineering Prioritisation Panel Meeting 3 and 4 December 2019 Announced
Summary on Grant Application Form
Electrical machines are estimated to contribute to more than 99% of global generation and more than 50% of all utilisation of electrical energy. Their role will be more pronounced as we move towards a more sustainable carbon neutral economy. Taking the UK automotive industry as an example, it is the fastest growing sector in the European economy, utilising more than 30% of our primary energy resources. UK automotive production is around 2 million vehicles in 2017. By renewing end of life products with more energy efficient ones, such as electric and hybrid electric vehicles (EV and HEV), this strong growth will increase the efficiency of energy use and help meet UK government targets in CO2 emission reduction - a 34% cut in 1990 CO2 emission levels by 2020 and 80% by 2050.

This trend of electrification in transport will lead to a huge demand in powertrain (machines and drives) research. To remain competitive, electrical machine manufacturers endeavour to increase power density and efficiency of electrical machines. However, the machine industry is a relatively mature sector and the margin for further improvement in machine efficacy and power density is slim without novel materials or radical cooling technologies. This is particularly the case for machine end-windings, which often have the highest temperature and hence have the biggest impact on machine achievable efficiency, power density and also life span. Methods such as spray cooling, flooded or semi-flooded stator are proposed for end-winding cooling. Both methods are very effective because the cooling fluid is in direct contact with the end-windings. However, due to corrosion and erosion of spray nozzles, the spray cooling suffers from reliability and robustness issues. Moreover, both spray cooling and flooded stator often require a closed circuit liquid (oil or deionised water) supply equipped with mechanical pumps, filters, etc. which adds to capital and operating costs while also leading to a reduction in effective machine power density.

In order to overcome the challenges facing the traditional cooling technologies, this project aims to develop a novel thermomagnetic liquid cooling for machine end-windings. The thermomagnetic cooling medium is based on ferro-fluid, which is an electrically nonconductive, temperature sensitive fluid mainly consisting of ferromagnetic nano-scale particles (such as iron, cobalt, nickel, etc.) in a liquid carrier (such as synthetic oils, hydrocarbons, etc.). When such liquid experiences a temperature variation under an external magnetic field, the fluid behaves as a smart fluid, i.e. it will have higher magnetisation in the lower temperature region (farther away from the heat source) than in the higher temperature region. As a result, a net magnetic driving force is produced to self-drive the fluid to flow towards the heated area (heat source with higher temperature). Due to this special feature, the thermomagnetic liquid cooling will be self-regulating, pumpless and maintenance free and hence very cost effective.

In this project, by adopting a multiphysics optimisation approach that combines electromagnetic and thermomagnetic domains into a single framework for machines with ferrofluid cooling, this project aims to achieve a temperature reduction of >30oC compared to a forced air cooled machine with rotor mounted fans. This is significant because the reduction in machine temperature, particularly the winding temperature, not only increases machine's life span, e.g. a 10oC increase in winding temperature will halve the winding insulation life (similar effect for bearings' life span), but also increases the machine's efficiency due to reduced power losses.
Key Findings
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Organisation Website: http://www.shef.ac.uk