Small Permanent Magnet Motor Research Articles

Investigation on high-power-density design of small PM motors focusing on air gap configuration

This paper describes a case study of high-power-density design of small permanent magnet (PM) motors focusing on their air gap configurations. Two types of the PM motors, i.e., a radial air gap type and an axial air gap type, are comparatively discussed. Comparison between the two types has been conducted from the viewpoints of I-T characteristics, N-T characteristics, efficiency maps, torque ripple characteristics, and so forth. It has been clarified that the axial air gap type has significant advantages to achieve the high-power-density under some limited condition.

Stator Shape Design Method for Improving Power Density in PM Motor

In this paper, we propose a stator shape design method for improving power density in a small permanent magnet motor. In order to calculate iron loss correctly, we analyze a motor by using 2-D finite element method (FEM) in which an E&S model is introduced. Moreover, external circuit equations are solved coupled with equations in electromagnetic field by FEM to calculate copper loss correctly. It is possible to calculate power density correctly by evaluating loss and weight of a motor correctly whether stator shape is changed. As a result, we show that our analysis technique is useful as a shape design method of a motor’s stator for improving power density.

Position-sensorless starting method and driving characteristics of closed-slot small permanent-magnet motor

This paper describes a method of estimating the rotor position of a surface permanent-magnet motor with a closed-slot stator for sensorless starting by using the effect of partial magnetic saturation. It also describes a starting scheme for the motor. Since the closed-slot stator is partially saturated at 12% of the rated stator current, this method reduces noise and vibration. Experimental results on the driving characteristics of the motor are also presented.

Anisotropic Nd-Fe-B based flexible bonded magnet for small permanent magnet motors

This paper reports the method of preparing axially oriented ring-shaped magnets for small motors from anisotropic HDDR powder.

The use of low-inertia integrating motors

The relative advantages and the performance of these small permanent-magnet motors which have, over a certain range, a speed proportional to the applied voltage, are discussed. The current-voltage characteristics, which allow the motor to be described by a simple equivalent circuit, are used to derive the speed-voltage characteristic when it is driven by a voltage source of appreciable internal resistance. Choice of the type of motor is discussed in relation to the integration of relatively large and of small voltages.

自動記録式無線ロボット検潮儀について

For the purpose of high water forecast, an automatic tide station which can send radio signals and can be operated at remote position, has been developed. The gauge consists of the transmitter and the receiving set. Both sets are controlled by the clocks, and the height of the tide is recorded on the chart once an hour. The frequency of the radio wave is 414 m_??_ sec-1.The principle of remote recording is that of so-called Olland system. Synchronization of the transmitter and the recorder is caused by a small permanent magnet motor with a speed regulater. The automatic zero adjust of the record is made by a long sign of the signal in every cycle, and the height of tide is marked with a dot by the short signs on the chart.These equipments have been tested at the Central Meteorological Observatory and the Tsukishima tide station in Tokyo, from Oct., 1953. The accuracy of the measurement of tide height was within about 1%.Power required for the transmitter is 6V 3W, for which 6 pieces of 500 AH air wet depolarized cells are used.