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The thermal management of electrical insulations poses a challenge in electrical devices as electrical insulators are also thermal insulators. Diamond is the best solid electrical insulator and thermal conductor. This can lead to a paradigm change for electrical machine winding and lamination insulation design and thermal management. The paper introduces these techniques and discusses its effect for the design of electrical machines and its potential consequences for electromagnetic analysis, for example, in multi-physics modelling. The diamond winding insulation is patent-pending, but the diamond enriched lamination insulation is published for the benefit of the scientific community.

The windings of electrical machines are insulated to avoid contact between the coil and other conductive components, for example, the stator core. The principle of using mica tape and resin impregnation has not changed for a century and is well established to produce main insulation on a complex conductor shape and size. These insulations have poor heat-conducting properties. Similarly, the insulation of laminated steel sheets comprising the stator and rotor restrict heat flow. Diamond-based insulation provides a new path. Increased thermal conductivity means reduced temperature rise and the reduced thermal time constants in multi-physics simulations and system analysis.

The largest benefit of a diamond-based core insulation is in electrical machines in which the losses are conducted axially to the coolant. These are machines with radial ducts and effective cooling in the end regions. The main benefit will be in reducing the number of radial ducts that positively affect the size, production costs and the copper losses of the machine. The increased thermal conductivity of the diamond insulation system will reduce the thermal constants noticeably. These will affect system behavior and the corresponding simulation methods.

Diamond insulation can lead to a paradigm change for electrical machine winding and lamination insulation design and thermal management. It might also lead to new modeling requirements in system analysis.

The purpose of this paper is to optimize the stator slot geometry of a high-speed electrical machine, which is used as an assist for a turbocharger. Meanwhile, the suitability of the Particle Swarm algorithm for such a problem is to be tested.

The starting point of the optimization is an existing design, for which the Particle Swarm algorithm is applied in conjunction with the transient time-stepping 2D finite element method.

It is found that regardless of its stochastic nature, the Particle Swarm work well for the optimization of electrical machines. The optimized design resulted in an increase of the slot area and increase of the iron loss, which was compensated by a dramatic decrease in the Joule losses.

The optimization was concentrated on the stator design whereas the rotor dimensioning was carried out withing the compressor and turbine design.

A turbocharger with electric assist is designed optimized and manufactured. The Particle Swarm algorithm is shown to be very stable.

The thermal design of high‐speed electrical machines is a greater challenge in comparison with conventional electrical machines. When designing the machine, the calculated temperatures in all parts should be lower than their critical temperatures. This paper aims to perform thermal analysis for different rotor types according to the level of shield from eddy currents in order to achieve a safe thermal design of the machine.

The machine under study in the paper is a high‐speed permanent magnet (PM) motor designed for speed n=31,500 rpm and power P=130 kW. A thermal‐network method was used for thermal analysis of the machine.

The minimum value of the coolant flow in the air gap that provides an effective cooling of the machine was estimated. The coolant itself is not able to provide an effective cooling of the magnets if they are not shielded from eddy currents.

The results are obtained only by the thermal‐network method. Numerical techniques and practical measurements for comparison and validation of the existing results should be implemented in future.

The paper offers useful practical information when a safe thermal design of a high‐speed PM electrical machine should be performed.

The paper demonstrates how three different design types of a high‐speed PM electrical machine are thermally analysed in order to find out which type fulfils the rigorous thermal criteria. The practical significance of the paper is beneficial for the designers of high‐speed PM electrical machines.