Masami Nirei

Comparative Evaluation on Power-Speed Density of Portable Permanent Magnet Generators for Agricultural Application

The comparative evaluation based on the power speed density of several types of portable Permanent Magnet Generator (PMG) considered for agricultural applications is presented. These generators are purposely designed to be used in agriculture sectors and thereby it should be of lightweight, small in size and ease to use. Six difierent generator topologies are developed for investigation of such purposes. A number of design parameters are considered to analyze the performance characteristics for each type of developed PMG. Based on the power speed density factor that is used to describe better generator performance, the suitable PMG for the agricultural application is identifled through a comprehensive evaluation.

Magnetic field analysis of a resolver with a skewed and eccentric rotor

Factory automation applications such as machine tools, etc., with high precision motion control require a feedback sensor with low speed-ripple for precise velocity control. The resolver is one of feedback sensors widely used in automation applications. Distorted signal-output related to speed fluctuations of the resolver result from permeance ripples, etc., produced by eccentricity of the rotor and stator slots in which coils are installed, and of the rotor itself. Although the permeance method has been used to analyze and determine the optimal magnetic design of a resolver, it remains an imperfect solution. This paper proposes a new magnetic field analysis method which offers the means to produce better analysis. The most significant feature of our method is that the skewed resolver rotor is divided into segments and the induced voltages of each segments are calculated and combined. Therefore, the analysis of the skew affect and the eccentricity of the rotor becomes possible by using the 2-D FEM (two-dimensional finite element method) with magnetic vector potential. The analyzed results of the spectrum in the induced dual phase voltage waveforms indicate the possibilities of close agreement with the measured values. These results confirm the validity of this method.

Effect of magnet size on torque characteristic of three phase permanent magnet brushless DC motor

This paper deals with a design of high torque brushless DC motor (BLDC). This motor is designed in new arrangement of the stator teeth and operated as three phase motor. This motor is developed to produce high torque performance motor that could be used as in-wheel motor for agriculture applications such as tractors. The basic structure and principle of the motor is described briefly. The simulation Finite Element Method (FEM) technique is used in order to analyze the performance of the motor including flux flow path and flux distribution. Various sizes of magnet had been varied for torque and motor efficiency analysis by using simulation and analytical method, respectively. This found that the maximum output torque is achieved when both length and width of magnet is at largest size. The result also signifies that the increment of torque will not determine the increases in the motor efficiency as well. In the end, this paper could be used as a further research for the future.

Positioning System for Sensor less Linear DC Motor

Linear motor has gain popularity as linear motion drive in office and factory automation which provides an alternative method to conventional rotary motor. Chip mounting is one of linear motor applications especially for linear DC motor (LDM). Displacement sensor which is normally used for positioning on the system, made the system expensive. This paper discusses the application of sensor less on positioning system for LDM. A spring is used to determine the position, while the spring displacement which is proportional to the thrust was produced by the motor. The thrust itself can be controlled by controlling the current supplied to the motor. Therefore, the positioning of LDM can be controlled by varying the current value. The approach used in this paper is to control the current is by manipulating various pattern of pulse width modulation (PWM) signal. As a result, the settling time less than 32 ms for 10 mm positioning has been achieved.

Considerations on electrical and mechanical time constants of a moving-magnet-type linear DC motor

The electrical and mechanical time constants of a moving-magnet-type linear DC motor (LDM) are required to have small values so as to realize a high-speed response LDM. Simplified expressions of the electrical and mechanical time constants of the LDM are derived using the permeance method. These constants are also computed using the finite element method (FEM) combined with the electric circuit equation. The measured electrical and mechanical time constants are 10.5 ms and 1.6 ms, respectively. The calculated values of the electrical time constant obtained by the permeance method and the FEM are 13.4 ms and 10.2 ms, respectively. The calculated values of the mechanical time constant obtained by the permeance method and the FEM are 1.6 ms and 1.5 ms, respectively. It is clarified that both methods are useful for calculating the electrical and mechanical time constants of the LDM.

Electromagnetic Design and FEM Analysis of a Novel Dual-Air-Gap Reluctance Machine

The electro-magnetic torque production in the reluctance machine is highly in∞uenced by the magnetic linkages in the air-gap area. The conventional machines derive the drawback of reduction in the air-gap area to a minimal due to in∞uence of mechanical unbalancing thereby restricting the efiective energy conversion area. In order to increase the magnetic linkage area, the dual-air-gap structure is introduced. The dual-air-gap structure is realised through the division of the magnetic circuit area into two air-gaps while still maintaining the net air-gap length value. A double-rotor with single- stator structure is used to attribute the above concept. The electro- magnetic analysis of such a structure is developed and investigated through numerical analysis. In order to validate the proposed structure the electro-magnetic characteristics are compared with that of the conventional structure at similar operating conditions. The maximum torque generated by the selected dual-air-gap structure is 1.7549Nm and for conventional structure is 1.2723Nm. The evaluation of the proposed machine is done at the same operating conditions and it is found that the dual-air-gap structure exhibit 65% increase in average torque value in comparison with that of the conventional single-air-gap structure.

Improvement of energy density in single stator interior permanent magnet using double stator topology

The paper presents the energy density improvement using magnetic circuit analysis of the interior permanent magnet motor. The leakage flux from the conventional structure is improved with modified magnetic circuit to improve the energy and thereby the torque value. This is approached with a double stator structure design. The proposed structure is investigated with two design variations, namely, the double stator with thin pole shoe and the double stator with thick pole shoe motors. Variations in the mechanical parameters of the all the developed models are analyzed through the finite element analysis tool. In all investigations the magnetic source is fixed in both the permanent magnet volume and coil magnetomotive force, respectively, as 400 mm3 per each pole and 480 Ampere turns per pole. From the analysis the best fit magnetic structure based on the torque characteristics is derived and is fabricated for the same volume as that of the conventional structure for performance evaluations. It is found out that there is improvement on the motor constant square density for the proposed improved magnetic circuit through the best fit double stator with thick pole shoe by about 83.66% greater than that of the conventional structure.

Development of a Linear Electromagnetic Actuator for Implantable Artifical Heart

This paper deals with the configuration, principle of operation, and experimental results concerning a linear pulse motor for an implantable aritificial heart. The linear pulse motor is designed to be as small as possible so as to minimize the space occupied. The mover is made of laminated Permendur sheets 0.35 mm in thickness. The stators are of the same material in orer to maintain a high saturation flux density. the motor develops a thrust of 60 Newtons with an input power of 2.72 Watts. The mass and volume of the motor are 320 g and 56.6 ml. The characteristic values (figures of merit) of the motor are 22.1 N/W, 1.1 N/ml and 0.19 N/g; these values are two to ten times superior to those of ordinary linear pulse motors, because of the use of Permendur sheets and rare-earth magnets (Sm2Co17).

Linear electromagnetic actuators for implantable artificial heart

Three kinds of linear electromagnetic actuator (LEA) have been designed and manufactured for use implantable artificial hearts.

Design and Performance Index Comparison of the Permanent Magnet Linear Motor

In this paper, a cylindrical permanent magnet linear motor (PMLM), which has a high performance, was designed and developed, because the motor has a zero normal force and a higher thrust density. The structure of the motor plays a vital role at the stage of design. During the design stage, several models of the PMLM that had different structural parameters were simulated using FEM software, and the model that produced the high-performance was identified. The structural parameters involved include the radius and height of the permanent magnet, rpm and hpm, the height of coil, hc ,a nd the shaft radius, rs, within a fixed total radius, rtotal. To prove its high-performance characteristics, the performance of the PMLM was then compared to the commercialized PMLM using four performance indexes which are thrust F , thrust constant kf , motor constant km and motor constant square density G. About 200 commercialized PMLMs with three different types have been chosen which are the slot type PMLM, slotless type PMLM and shaft motor. Based on the comparisons, the designed PMLM had a better performance than the commercialized PMLM. In order to validate the simulation result, the PMLM was manufactured. The simulation and measurement static thrust characteristics were then compared, and it was found that the simulated thrust had a good agreement with the measured one.