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Two new models for specific power losses in cold-rolled motor lamination steel are described together with procedures for coefficient identification from standard multifrequency Epstein or single sheet tests. The eddy-current and hysteresis loss coefficients of the improved models are dependent on induction (flux density) and/or frequency, and the errors are substantially lower than those of conventional models over a very wide range of sinusoidal excitation, from 20 Hz to 2 kHz and from 0.05 up to 2 T. The model that considers the coefficients to be variable, with the exception of the hysteresis loss power coefficient that has a constant value of 2, is superior in terms of applicability and phenomenological support. Also included are a comparative study of the material models on three samples of typical steel, mathematical formulations for the extension from the frequency to the time domain, and examples of validation from electrical machine studies. Index Terms--Brushless permanent-magnet (BLPM) motor, cold-rolled motor lamination steel, core loss, electric machine, Epstein test, finite-element analysis (FEA), interior permanent-magnet (IPM) motor, iron loss.

For the calculation of torque in brushless (BL) alternating current motors a local method is proposed, based on the Maxwell stress theory and the filtered contributions due to the harmonics of the magnetic vector potential in the motor air gap. By considering the space fundamental field only, the method can efficiently estimate the average synchronous torque for a variety or motor topologies, including concentrated winding designs. For BL direct current motor analysis a global method is introduced, based on the virtual work principle expressed in terms of energy components in various motor regions. The method leads to simplifications in the average torque calculation and enables the direct identification of the cogging and ripple components. The mathematical procedures have been validated against experiments and other numerical techniques. Index Terms--Brushless (BL) permanent-magnet (PM) motor, cogging torque, electric machine simulation, finite-element analysis (FEA), ripple torque, synchronous machine.

This paper describes a general method for preliminary design of fast-acting solenoid actuators. Moving armature, drive circuit, and nonlinearities are modeled, as well as eddy currents for solid iron devices. The electromagnetic model is obtained by computing two magnetization characteristics corresponding to the extreme positions of the armature and a novel interpolation function for the intermediate positions. This function, characterizing the magnetic configuration of the actuator, is computed analytically and leads also to an analytical formulation of the magnetic force. In order to achieve extremely fast computation, eddy currents are modeled through a new type of electric equivalent network, derived directly from Maxwell's equations and taking into account the actual BH nonlinearities, moving armature, and device geometry. The method is demonstrated on a pot-core solenoid actuator and compares favorably with finite-element results and measurements. Index Terms: Dynamic design, eddy current, reluctance network, solenoid actuator.

In this paper, a multiobjective design optimization method combining design-of-experiments techniques and differential-evolution algorithms is presented. The method was implemented and utilized in order to provide practical engineering insights for the optimal design of interior and spoke-type permanent-magnet machines. Two combinations with 12 slots and 8 poles and 12 slots and 10 poles, respectively, have been studied in conjunction with rare-earth neodymium-iron-boron (NdFeB) and ferrites. As part of the optimization process, a computationally efficient finite-element electromagnetic analysis was employed for estimating the performance of thousands of candidate designs. Three optimization objectives were concurrently considered for minimum total material cost, power losses, and torque ripple, respectively. Independent variables were considered for both the stator and rotor geometries. A discussion based on a systematic comparison is included, showing, among other things and despite common misconception, that comparable cost versus loss Paretos can be achieved with any of the rotor topologies studied. [ABSTRACT FROM PUBLISHER]

A model of core losses, in which the hysteresis coefficients are variable with the frequency and induction (flux density) and the eddy-current and excess loss coefficients are variable only with the induction, is proposed. A procedure for identifying the model coefficients from multifrequency Epstein tests is described, and examples are provided for three typical grades of non-grain-oriented laminated steel suitable for electric motor manufacturing. Over a wide range of frequencies between 20-400 Hz and inductions from 0.05 to 2 T, the new model yielded much lower errors for the specific core losses than conventional models. The applicability of the model for electric machine analysis is also discussed, and examples from an interior permanent-magnet and an induction motor are included. [ABSTRACT FROM AUTHOR]