David Gerada

Design Aspects of High-Speed High-Power-Density Laminated-Rotor Induction Machines

This paper deals with the considerations associated with the design of high-speed high-power-density laminated-rotor induction machines (IMs). The considerations discussed are described by the design of an actual 10-kW machine, which runs at speeds of up to 75 kr/min with a rated power density of 28 MW/m3 for an electrically assisted turbocharger. Using a developed multidomain design environment which puts equal weight on the electromagnetic, mechanical, and thermal aspects, the rotor split ratio, electric and magnetic loadings, lamination material, rotor-bar material, and rotor-bar shape are identified as important and sensitive parameters in the design of high-speed IMs. Finally, general guidelines for designing high-speed high-power-density IMs are presented.

A High-Speed Permanent-Magnet Machine for Fault-Tolerant Drivetrains

This paper details the design considerations of a permanent-magnet three-phase synchronous machine for fault-tolerant operation. A multidisciplinary approach to the optimal design of the machine is adopted, targeted at minimizing the additional losses resulting from faulty operating conditions and accounting for the remedial control strategy implemented. The design of a closed-slot six-slot four-pole machine is presented. The machine is prototyped and tested to validate the analytical-computational performances predicted in the design and analysis stage under healthy and faulty conditions.

High speed electrical generators, application, materials and design

This paper highlights the advancement in high speed generation applications along with describing the state of the art in the materials and technologies enabling such an application uptake. Following the introduction, highlighting the current situation in the energy market, the first section describes some recent developments in materials used in the construction of a high speed drive. Various application areas are dealt with in section three and the state of the art along with design considerations of various machine topologies are discussed in section four. In section five a case study is presented highlighting the preliminary design procedure used to select a machine topology for a given application. Finally a summary discussing the design flow required when attempting such high speed design is presented in section six.

Electrical machines for high speed applications with a wide constant-power region requirement

This paper discusses the issues associated with the design of high speed machines with a wide constant-power region requirement. Using described multi-physics design environments, which put equal weight on the electromagnetic, thermal and mechanical considerations, the suitability and power density achievable using Induction Machines (IM) and Permanent Magnet Synchronous Machines (PMSM) are compared.

Design issues of high-speed permanent magnet machines for high-temperature applications

This paper deals with the issues associated with the design of high-speed, high torque-density permanent magnet machines which operate in elevated temperature environments. The considerations discussed are described by the design cycle iterations of a 23kW machine, which runs at a speed of 84krpm, with a rated rotor torque density of 50kNm/m3. Particular emphasis is made on the interaction (and conflict) of electromagnetic fields, thermal fields and mechanical constraints in finding an optimum air-gap length for minimum magnet temperature and best overall efficiency.

Optimal design of a high speed concentrated wound PMSM

This paper looks at the design of a high speed permanent magnet synchronous machine for maximum power density. Machines with sub-unity slots per pole per phase are characterised by low cogging torque, high slot fill and short end windings which contribute to lower copper losses. However such machine topologies tend to have a harmonic-rich armature reaction field which may contribute significantly to the rotor eddy current losses. In this paper a thermal model grafted into an analytical model able to estimate the losses in the rotor conducting components is used to compare a number of machine designs.

Improved Damper Cage Design for Salient-Pole Synchronous Generators

The benefits of implementing a damper winding in salient-pole synchronous generators are widely known and well consolidated. It is also well known that such a winding incurs extra losses in the machine due to a number of reasons. In order to improve the overall efficiency and performance of classical salient-pole, wound field synchronous generators that employ the traditional damper cage, an improved amortisseur winding topology that reduces the inherent loss is proposed and investigated in this paper. This is essential in order to meet modern power quality requirements and to improve the overall performance of such “classical” machines. The new topology addresses the requirements for lower loss components without compromising the acceptable values of the output voltage total harmonic distortion and achieves this by having a modulated damper bar pitch. As vessel for studying the proposed concept, a 4-MVA salient-pole synchronous generator is considered. A finite element model of this machine is first built and then validated against experimental results. The validated model is then used to investigate the proposed concept with an optimal solution being achieved via the implementation of a genetic algorithm optimization tool. Finally, the performance of the optimized machine is compared to the original design both at a steady state and transient operating conditions.

End barrier shape optimizations and sensitivity analysis of synchrnous reluctance machines

This paper presents an extensive study on the electromagnetic and structural influences of the end barrier shape of a Synchronous Reluctance Machine (SynRel). One of the most challenging tasks in designing these machines is to achieve a smooth torque and a mechanically robust structure, especially when high operating speed range is required. Several papers have already addressed the electromagnetic design problem related to the choice of the flux barriers thicknesses and positions. However a comprehensive work on the influence of the end part of the flux barrier on the electromagnetic and structural performance has not been yet presented. In this work two end barrier shapes are considered and optimized using the same methodology. Then the optimized machines have been deeply analyzed in terms of torque, torque ripple and rotor von Mises stress distribution. Furthermore, with the aim to further investigate the influence of such end barrier shape, a detailed sensitivity analysis is presented. In conclusion, general guidelines for the structural and electromagnetic design of such end barrier shape are drawn.

A topology selection consideration of electrical machines for traction applications: towards the FreedomCar 2020 targets

This paper details a qualitative comparison between different types of electrical machine for hybrid electric vehicle traction applications. Targets set by the US Department of Energy for the year 2020 are used as goals. Several types of machine for this application will be discussed, focusing on the benefits and challenges of each machine when applied to these targets. Then the machines are compared based on appropriate quality indices relative to general performance characteristics. It is shown that the interior permanent magnet machine is the most suited topology for traction applications with these challenging targets. Two machine designs for these targets are briefly compared at the end of the paper.

High speed solid rotor induction machine: Analysis and performances

The paper presents the design, analysis and testing aspects of high speed induction machines equipped with solid rotor. At first the theoretical background and design aspects of solid rotor for induction machines is presented considering electromagnetic, thermal and mechanical aspects and focusing on the assessment of end-region factor effects. The techniques are benchmarked against a 120 kW solid rotor induction motor designed for power generation application.