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This paper studies the design of electric machine windings with reduced magnetomotive force (MMF) space harmonic content by adjusting the slot distribution and coil turns. Closed-form expressions for the winding factor and harmonic magnitudes established from a mathematical representation of winding functions are used to formulate the MMF space harmonic suppression problem. The framework is applicable to both distributed windings and fractional-slot concentrated windings (FSCWs) and can be solved with different techniques. No special requirements on the slot/pole combination and the number of layers are necessary. One example uses a linear algebraic technique to solve simultaneous equations and the result is a mixed-layer distributed winding. The process also reveals the criterion when multiple requirements on the winding factor and harmonic magnitudes can be satisfied concurrently. Contour plots are included to provide additional graphical insight. Another example designs a 24-slot 22-pole FSCW subset with numerical optimization. The resultant winding is a four-layer FSCW with two subsets and 3/4 of the harmonic orders are eliminated. The performance improvement of this winding is verified with finite-element simulations. [ABSTRACT FROM PUBLISHER]

This paper proposes a systematic approach for the development of electric machine windings with reduced magnetomotive force (MMF) space harmonic content. By identifying the levels and slot position angles in the winding function of an electric machine winding, the winding factor, the magnitudes of individual harmonic components and thus the MMF spectrum of a winding can be represented mathematically as functions of the levels and angles. With numerical optimization, these functions can act as the constraints and the objective function. A typical formulation is to limit the magnitudes of undesired harmonics and to maximize the winding factor of the working component. The result of the optimization is often a new winding layout with potentially unequally pitched slots and different turns for the coils within a phase, and reduced or even eliminated harmonic orders of design interest, while maintaining a reasonable winding factor. The mathematical representation and design approach is applicable to both distributed windings and fractional-slot concentrated windings (FSCWs), with no special requirements on the slot/pole combination and the number of layers. Two design examples, a mixed-layer distributed winding and a 24-slot, 22-pole double-layer FSCW, are shown to have improved electromagnetic performance with finite element simulations. [ABSTRACT FROM AUTHOR]

The behavior of rotor eccentricities in current-regulated interior-permanent-magnet machines is investigated. The study focuses on two typical topologies of significant industrial relevance: machines with distributed windings with two slots per pole and phase and motors with concentrated coils and three slots per pole pair. The effect of stator-winding parallel paths is examined for both cases. Coil and terminal electrical quantities and radial forces were simulated using finite-element analysis. Unbalanced operation, where the currents are not equal in parallel phase connections due to eccentricity, is also investigated. Experimental measurements of electrical quantities and forces on motors with static eccentricity are carried out using two special test setups. The experimental measurements validated the simulation results. [ABSTRACT FROM AUTHOR]

Zero-to-low-speed flux/rotor-position self-sensing techniques rely on the interaction of saliencies (asymmetries) with an injected signal or special switching pattern in the inverter to produce a response which contains information about the location of the saliency. In this paper, three types of deterministic spatial rotor position saliencies are introduced into an induction machine (IM). The saliencies were created by modulating the following: 1) the rotor bridge opening width; 2) the rotor bridge opening height; and 3) the rotor bridge opening fill. The influence of saliency geometric design variables on the self-sensing and power conversion properties is determined using a design of experiments and response surface methodology. An example IM design, which maximizes the self-sensing properties while preserving power conversion abilities, is presented. Modulation of the rotor bridge fill appears to be the least desirable saliency type. Both rotor bridge opening width and height modulations can be used successfully, but the rotor bridge opening width modulation requires extra simulations to characterize the self-sensing properties. [ABSTRACT FROM AUTHOR]