Multi-Objective Tradeoffs in the Design Optimization of a Brushless Permanent-Magnet Machine With Fractional-Slot Concentrated Windings

Abstract

In this paper, a robust parametric model of a brushless permanent magnet machine with fractional-slot concentrated windings, which was developed for automated design optimization is presented. A computationally efficient finite-element analysis method was employed to estimate the dq-axes inductances, the induced voltage and torque ripple waveforms, and losses of the machine. A method for minimum effort calculation of the torque angle corresponding to the maximum torque per ampere load condition was developed. A differential evolution algorithm was implemented for the global design optimization with two concurrent objectives of minimum losses and minimum material cost. An engineering decision process based on the Pareto-optimal front for 3,500 candidate designs is presented together with discussions on the tradeoffs between cost and performance. One optimal design was finally selected, prototyped and successfully tested.Index Terms-Differential evolution (DE), finite-element analysis, fractional-slot concentrated winding, multi-objective design optimization, permanent-magnet (PM) machine.

Large-scale electromagnetic design optimization of PM machines over a target operating cycle

“…Depending on the particular application, the design optimization methods of electric machines [1][2][3][4][5][6][7] aim at realizing a set of objectives under certain performance constraints described in the optimization fitness function. Regardless of the type of motor and the objectives/constraints under which the optimization is performed, whether optimizing for constant torque [6] or constant power [7] operations, the automated design techniques evaluate the associated fitness function at the rated torque and base speed.…”

“…Regardless of the type of motor and the objectives/constraints under which the optimization is performed, whether optimizing for constant torque [6] or constant power [7] operations, the automated design techniques evaluate the associated fitness function at the rated torque and base speed. However, in many applications the optimized motor is to operate with variable frequency drives at various load operating points.…”

Identification of design rules for interior PM motors with different cooling systems

“…Recent design trends rely on large-scale design optimization techniques based on electromagnetic (EM) finite element (FE) analysis of design candidates for high fidelity calculation of their performance metrics [7][8][9][10][11][12]. In some studies, coupled EM/thermal models are incorporated to accurately determine the maximum current density for a given machine configuration [11,12].…”

“…In some studies, coupled EM/thermal models are incorporated to accurately determine the maximum current density for a given machine configuration [11,12]. In others, a fixed current density with respect to the machine's cooling system has been assumed [7][8][9][10]. The latter approach is faster and can be as effective as the former provided that the thermal limits are examined in selection of the optimized designs.…”

Groove depth determination based on extended leakage factor in a 12-slot 10-pole machine

“…Fractional slot machines (FSM) are received a great attention since they allow concentrated windings, high pole structure, and less torque ripple [1] and [2]. Concentrated windings are preferred when it is required to increase the slot fill factor and to reduce the length of end windings.…”