The design of energy-efficient electric motor is a complex problem since diverse requirements and competing goals have to be fulfilled simultaneously. Therefore, different approaches to the design optimization of electric motors have been developed, each of them has its own advantages and drawbacks. The characteristics of these approaches were presented in the previous part of this multipart paper. In this paper, the presented approaches will be assessed with respect to the criteria: degrees of freedom, computing time and the required user experience. A conflict of objectives will become apparent. Based on these findings, requirements for a new design optimization method with the aim to solve the conflict of objectives, will be formulated.

Energy-efficient electric motors are gathering an increased attention since they are used in electric cars or to reduce operational costs, for instance. Due to their high efficiency, permanent-magnet synchronous motors are used progressively more. However, the need to use rare-earth magnets for such high-efficiency motors is problematic not only in regard to the cost but also in socio-political and environmental aspects. Therefore, an increasing effort has to be put in finding the best design possible. The goals to achieve are, among others, to reduce the amount of rare-earth magnet material but also to increase the efficiency. In the first part of this multipart paper, characteristics of optimization problems in engineering and general methods to solve them are presented. In part two, different approaches to the design optimization problem of electric motors are highlighted. The last part will evaluate the different categories of optimization methods with respect to the criteria: degrees of freedom, computing time and the required user experience. As will be seen, there is a conflict of objectives regarding the criteria mentioned above. Requirements, which a new optimization method has to fulfil in order to solve the conflict of objectives will be presented in this last paper.

Designing energy-efficient electric motor is a task where multiple goals have to be achieved at once. To find the best design possible, different approaches have been developed. In part one of this multipart paper, the characteristics of the design optimization problem and methods to solve them have been presented. Part two will deal with the different types of model descriptions and how the fundamental workflows look like. The third and last paper will evaluate the findings concerning the solution methods of the design optimization problem of electric motors. As a consequence, requirements for a new improved optimization method are deduced and presented.

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Designing electric motors is a task, where various requirements and objectives have to be met simultaneously. To achieve this, different approaches to the design optimization problem of electric motors have been developed. Especially today, one of the most important properties of an electric motor is its efficiency. Therefore, it is important to include the efficiency into the design process since at this stage, gains in energy efficiency can be made very cost-effective. Typically, state of the art is to consider only distinct operational points and not the whole operational cycle in the design optimization.To demonstrate that the whole working cycle of an electric motor should be included into the design optimization, is subject of this paper. Based on a literature survey of recent design optimization methods the current state of the art will be presented. The main objective of this paper is dedicated to the design of a permanent magnet synchronous motor. Using genetic algorithms, the motor will be designed several times with varying operational points. As will be seen, for the sake of minimal energy requirement, the whole working cycle and not only distinct operational points have to be considered in the design optimization.