A core business of Cummins Inc. is that of power generation and conversion. On this front, the UoN has been working with Cummins Generator Technologies (CGT) for more than 2 decades. Within the CIC, it is therefore natural that one of the main fields of research is related to power generation and conversion. A number of projects and investigations aimed at improving generating systems, (with the main focus on the synchronous generator (SG) itself) are ongoing. The objective is to enhance and complement CGT’s already impressive range of machines.

Analytical and numerical tools are being constructed to allow for fast and accurate multi-physics modelling for design optimisation and refinement. The more exciting and innovative ideas being considered include: skew-less SGs,  exciter-less SGs and solid rotor machines. As frequently noted, most of these projects are aimed at improving performance and reducing machine size and cost.

Another exciting area related to this field is manufacturing of such machines. Taking advantage of the Advanced Manufacturing group’s expertise, new and innovative manufacturing processes for SGs are being developed with the aim of achieving more efficient and effective, flexible processes. 

Thermal management of electrical machines, power electronics and drives plays a very important role in the understanding and enhancing of the efficiency and lifetime of all machines and drives. Thermal performance is modelled using a combination of ‘Lumped Parameter Thermal Network’ (LPTN) and conjugate heat transfer ‘Computational Fluid Dynamics’ (CFD) modelling.

A range of machine sizes are investigated, including those with complex axial and radial cooling ducts. Extensive experimental testing provides airflow and thermal data, which is also used for validating and fine tuning models.

Alongside the improved modelling of the thermal characteristics of machines, innovative cooling methods are being investigated and applied to allow for higher current densities and higher frequencies, aimed at increasing achievable power densities. 

Electrical drives designed to operate at high speeds result in higher power densities, however they have significant challenges in high centrifugal forces and higher machine losses. The research that the CIC is working on considers the impacts of high speed rotation upon the rotor, ways to overcome the forces and losses and the impact of high switching devices on the lifetime of machines and power electronics.

Solid rotor induction machines are being investigated to push speed boundaries. The rotors designed for this are incredibly robust and able to withstand high forces. This has allowed new maximum peripheral speeds, and therefore excellent power densities, to be achieved.

Another high speed application is power generation from engine waste heat recovery. Previously, PM machines have been used for this. Members of the CIC have developed a reluctance machine which can achieve the same performance without the need for high PM masses.

Another core business of Cummins Inc. is hybrid electrical vehicles. Currently, Cummins produce an electrical machine for large hybrid vehicles. Traction machine research in the CIC takes two main routes from this.

The first is looking into ways to improve the machine for the current specifications, including designs to reduce cost, improving the control and providing higher torque across a wider speed range. The primary focus of this work has been on a wound field flux switching machine with novel pole shoes in the rotor. 

The other route is the investigation into the US Department of Energy FreedomCar 2020 targets, aimed at smaller plug in hybrid electric vehicles. These are a set of challenging targets requiring advancements in cost, efficiency and power density. The process for this work was to perform a trade-off study, starting with comparing all applicable machine types (including alternative and unusual designs), then comparing designs within the selected topology and finally optimising the design to minimise losses. 

The CIC also explores the technologies that surround electrical machines such as the above mentioned power electronics and drives. Other areas include active magnetic bearings to allow for completely frictionless rotation, stop start systems for traction, dc to dc conversion, waste heat recovery systems and modelling and analysis of systems. As a final note to this brief (not comprehensive) introduction, it is important to mention the CIC’s push towards the realm of multi-physics analysis and development. This includes electromagnetic, thermal and mechanical simulations and real-time design iterations.