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In the high-speed operation of SRM, the conventional pulse width modulation (PWM) drive method is not available because of the limitation of switching speed; therefore the single-pulse drive method is commonly employed. On the contrary, the use of the single-pulse drive method cannot avoid the overcurrent in the low-speed operation because of the insufficient back emf and the difficulty of duty control. With these reasons, the switching method is commonly changed from PWM at the low-speed operation to the single-pulse method at the high-speed operation. In the fan application, the required load torque increases as a square of the fan speed; it requires more current for the torque generation. Therefore at the mode transition between PWM and single-pulse drive, it is unavoidable that the phase current rapidly increases if the nonlinearity of inductance to the current is not considered. In this paper, by using finite element method (FEM) which is considered with the nonlinearity of the inductance with respect to the current, the speed of mode transition is calculated (18 000 rpm) and verified by the experiment.

This article introduces a single phase flux-reversal machine (FRM) and presents the design method to improve its starting torque. The effects of the design parameters on the characteristic and starting torque are analyzed by the finite element method. The design variables considered are tapered airgap, stepped airgap, slotted teeth, and asymmetric PM width. As a result, we can find the best model in producing starting torque of a single phase 2∕3 FRM.

In order to simulate the dynamic characteristics, we have developed a method of calculating the force of the linear dc motor screen door system which is using three-dimensional data of flux density in air gap from finite element analysis. We use the coil mesh data to calculate Lorentz forces of each coil. Then they are used for the dynamic characteristic analysis. The simulated dynamic characteristic is compared with experimental value.