Noriaki Fukushima

Iron-Loss Modeling for Rotating Machines: Comparison Between Bertotti's Three-Term Expression and 3-D Eddy-Current Analysis

Two calculation methods for iron-loss estimation of rotating machines are investigated. One is based on the conventional three-term expression. In this case, the losses are calculated from the time variation in the flux density obtained by the finite element analysis, which approximates the stator and rotor cores as solid magnetic materials without conductivity. The other is based on the 3-D eddy current analysis in the electrical steel sheet. In this case, the excess loss is calculated with a simple approximation. It is clarified that both methods can estimate the no-load iron loss in the similar accuracy and that the method based on the eddy-current analysis is suitable for the estimation of high-order harmonic iron losses.

Iron Loss Model for Rotating Machines Using Direct Eddy Current Analysis in Electrical Steel Sheets

In this paper, we propose and validate a method for the accurate estimation of iron loss in rotating machines. In this method, the eddy current loss in electrical steel sheets is directly calculated by nonlinear time-domain electromagnetic field analysis with a simple approximation of the excess loss. The hysteresis loss is also estimated by considering the flux distribution along the thickness of the steel sheet. The advantage of the method is that the high-frequency harmonic losses can be calculated accurately using only few material constants. The validity of this method is confirmed by experiments performed on a ring specimen and several types of motors. The experimental and calculated iron losses in each experiment are found to be in good agreement. It is clarified that the proposed method is useful for the accurate estimation of higher order harmonic losses, particularly, carrier losses caused by inverters.

Experimental validation of iron loss model for rotating machines based on direct eddy current analysis of electrical steel sheets

In this study, we propose and confirm an accurate estimation method of iron loss in rotating machines. In the method, the eddy-current loss in the electrical steel sheets is directly calculated by a nonlinear time-domain electromagnetic field analysis with a simple approximation of the excess loss. The hysteresis loss is also estimated with the consideration of flux distribution along the thickness of the steel sheet. The advantage of the method is the accuracy of the high-frequency harmonic losses using only several material constants. The validity of the method is confirmed by two experiments. The first experiment is carried out by a ring specimen of the electrical steel sheets. In this case, superimposed fundamental and harmonic fluxes are applied to the specimen. The second experiment is carried out by an induction motor driven by an inverter as well as a sinusoidal power supply. The carrier harmonic loss by the inverter is separated for the purpose of confirming the accuracy of the calculated harmonic losses. The experimental and calculated iron losses in both experiments are found to be in good agreement.

Torque and loss calculation of rotating machines considering laminated cores using post 1-D analysis

A post 1-D analysis of laminated cores is developed for estimating the torque and loss in rotating machines. The 1-D nonlinear eddy-current analysis along the thickness of electrical steel sheets is carried out at each element in the main finite-element analysis in order to estimate the loss and the harmonic torques caused by the eddy currents and the hysteresis phenomenon in the core. The proposed method is applied to several kinds of rotating machines. It is revealed that the accuracies of the torque and loss are significantly improved by the proposed method as compared to those of the conventional finite element method without notable increase in the computation time.

Characteristics Analysis of Large High Speed Induction Motors Using 3-D Finite Element Method

The characteristics of MW-class high speed induction motors are analyzed by 3-D finite element methods. First, several approximations are applied to the analysis in order to reduce the computation time without the deterioration of accuracy. Then, the calculated characteristics are compared with the experimental results in order to verify the proposed method. Finally, the loss generation mechanism of the motor is revealed by analyzing the harmonic electromagnetic fields. It is clarified that the combination of the 2-D and the one rotor slot 3-D finite element methods is suitable for the analysis of the motors. By using this method, the largest harmonic loss component of the motor is successfully specified.