The history of motor technology began with the discovery of electromagnetic induction by Faraday. Various kinds of motors were developed by the recent progress of the fundamental technology (magnetic structure, magnetic material, drive circuit, control method). Especially, motors using the reluctance torque have many advantages and some of them are used as high efficient motors. This paper overviews recent advances of reluctance torque assisted motors such as Switched Reluctance Motor (SRM), Synchronous Reluctance Motor (SynRM) and Interior Permanent Magnet Synchronous Motor (IPMSM).

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In this paper, we propose a method to calculate the equivalent circuit parameters of interior permanent magnet motors including iron loss resistance using the finite element method. First, the finite element analysis considering harmonics and magnetic saturation is carried out to obtain time variations of magnetic fields in the stator and the rotor core. Second, the iron losses of the stator and the rotor are calculated from the results of the finite element analysis with the considerations of harmonic eddy current losses and the minor hysteresis losses of the core. As a result, we obtain the equivalent circuit parameters i.e. the d-q axis inductance and the iron loss resistance as functions of operating condition of the motor. The proposed method is applied to an interior permanent magnet motor to calculate the characteristics based on the equivalent circuit obtained by the proposed method. The calculated results are compared with the experimental results to verify the accuracy.

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In this paper, we propose a new Hybrid type SRM with salient pole stator, which has a pair of permanent magnets attached symmetrically between the iron poles of the rotor. The paper describes experimental results of not only basic characteristics of the Hybrid SRM but also characteristics with current control loop under optimized advanced firing angle and cut-off angle. Considerable improvement of machine performance, especially efficiency and power factor, in the Hybrid SRM over conventional VR type SRM is confirmed.

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Recently, switched reluctance motors have attracted attentions from industries. It is a common practice to develop several test machines for performance evaluation. One way to make a comparison among several test machines is to draw an efficiency map in a speed and torque plane, however, it is rather complicated. For an easy comparison, a machine parameter measurement with an egg-shaped diagram has been proposed by the authors. In this method, it is possible to measure a inductance ratio, which indicates the saliency of switched reluctance machines. In this paper, a calculation of tolerance between theoretical egg-shaped curves and measured powers is proposed. It is found that the tolerances are within 4% as a result of several test machines. Although discrepancies in instantaneous current waveforms and voltage phase angles are seen, the obtained machine parameters indicate an exact relation between input power and required apparent power.

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The synchronous reluctance motors operated by a PWM inverter can be designed for the maximum saliency ratio (L_d/L_q). The saliency ratio is the most important parameter for achieving a high torque capability, high power factor and wide constant-power speed range. Generally, flux guides for the d-axis and flux barriers for the q-axis are provided to achieve a high L_d and low L_q, respectively, in order to maximize the saliency ratio. In this paper, the optimal shape and thickness of the flux barriers are investigated analytically. It is also demonstrated that the optimal rotor flux barrier shape can be expressed as the contour line of the function that shows the magnetic potential in a uniform material rotor. The effects of the magnetic resistance of the stator and the gap are also analyzed.

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Hydraulic pump units are widely used to operate hydraulic actuators. In a typical machine shop, conventional constant speed hydraulic pump units consume more than 20% of the total electric power necessary to operate CNC machine tools. Most of that energy are wasted to run the axial piston pump at idle. This paper describes a variable speed hydraulic pump unit using a switched reluctance motor (SRM), which saves energy drastically. SRM was selected as the most suitable motor for this application. Design and control strategy of this motor are described. Application examples to machine tools shows the effectiveness of the new hybrid pump system in saving energy and in reducing acoustic noise.

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Recently, Switched Reluctance Motors (SRM)have been applied to several industrial products such as fans, blowers, pumps and so forth because of their simple construction and relatively high e ciency.As one of the examples, Daikin Industries Ltd.has been successful in manufacturing hydraulic pump unit using 2.2kW three-phase SRM with shaft mounted position sensor for its control. This paper presents the position sensorless drive o the SRM for the purposes of reducing cost and down sizing of the hydraulic pump unit system.The controller, intentionally designed for this special application, realizes the following characteristics;the maximum and minimum speeds are 5000 and 300rpm, the speed response between the maximum and minimum speeds is within 100msec and the starting torque is less than 20% of the rated torque.The experimental studies using the hydraulic pump unit show that the proposed sensorless control scheme satis es the requirements for this application.

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This paper presents a voltage source half bridge series load resonant ZCS-PDM high frequency inverter using IGBT power module for the induction-heating roller in copy machines. The steady-state operating principle and unique features of this high frequency inverter with two ZCS-assisted inductive snubbers in series with the active power switch are presented, which can achieve stable zero current soft commutation under pulse density modulated power regulation scheme. The experimental results of cost effective ZCS-PDM inverter treated here are evaluated on basis of computer simulation ones and discussed for the induction-heating roller from a practice point of view

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A novel prototype of a double two-switch forward transformer linked zero-voltage and zero-current mode soft-switching (ZVZCS) pulse width modulation (PWM) DC-DC power converter using IGBTs for high power applications is presented. Based on a conventional two-switch forward transformer linked PWM DC-DC converter topology, this converter circuit configuration doesn't include any complex auxiliary resonant circuit. Combining two identical two-switch forward type DC-DC power conversion circuits with a tapped-inductor type DC smoothing filter into a power DC-DC conversion system makes it possible to achieve soft-switching conditions for the active power switches with aid of lossless snubber capacitors and transformer parasitic inductors. Lowered peak voltage across the power switching devices and their related peak current stresses, no transformer saturation effect, reducing of idle and circulating currents through circuit components are practically attained for this converter. This soft-switching PWM DC-DC power converter has some unique advantages such as better power conversion efficiency, lowered output DC ripple current, high power density, constant frequency PWM control scheme, cost effective and wide soft-switching operation range under load variations and PWM regulation settings for high power utilizations. The basic operating principle of the new soft switching power converter treated here is illustrated with approximate periodic steady-state circuit analysis for each mode equivalent circuit. The practical effectiveness of the proposed soft-switching DC-DC power converter is confirmed by the simulation results and is experimentally evaluated on basis of 500W-100kHz breadboard setup using the fast switching IGBTs.

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Experimental date are used to analyze conducted EMI noises which are produced in a motor drive system with power converters comprised of a converter and an inverter. The processes are investigated in which common mode noises (voltages and currents) are strongly influenced by voltage fluctuations occurring due to switching operations. It is found that the common mode currents are resonance currents which appear in series resonance circuits distributed in the motor drive system. The circuits have various kinds of resonance frequencies related to voltage fluctuations produced by switching operations and micro-surge voltages generated at the terminal of machines such as an ac rector or a motor. Thus, parameters of the distributed series resonance circuits are estimated using the transient waveforms obtained by separating the common mode current into waves analyzed by the FFT method. It is proved through simulations and experiments that the proposed circuit models closely represent actual electric circuits for common mode current paths distributed in the motor drive system.

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A new position sensorless control method is proposed for interior permanent magnet (IPM) synchronous motor drives at low speed and standstill. The method utilizes the dependence of inductance on rotor position in IPM. To estimate the position error directly, high frequency waves are injected to the motor voltage. The estimation is achieved by using ripple components of the motor current caused by injected waves. The controller directly estimates the error of rotor position, and adjusts the phase angle to the rotor position. At the initial position estimation, it is possible to estimate the initial rotor position including the direction of the magnetization. The basic idea, computer simulation and experimental results are discussed in this paper.

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Most Industrial robots are driven through reduction gears such as harmonic drives and RV gears. Since the exibility of the drive system, the vibratory behavior is caused duringthe operation. When the exibility is considered, the drive system of the robot joint can be modeled as a resonant mechanical system called two-inertia system. Two-inertia systems are the vibratory systems that have poles on/near the imaginary axis. Acceleration feedback and torque feedback are known as the vibration control methods of two-inertia systems. In this paper, we consider the two-inertia system with the feedbacks of motor-acceleration, load-acceleration and torsion-torque. It is shown that each feedback works to control the inertia-ratio of two-inertia system. Then, the control performances are compared. Torsion vibration in robot joint, which occurs owingto the accuracy of components and assembly error of gears at a certain speed of rotation, becomes a problem. In order to suppress the torsion vibration, each feedback is applied to the robot arm. As a result, the torsion vibrations are suppressed e ectively.

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In the superconducting maglev system, it is important to develop a non-contact on-board power source without environmental pollution such as noise and exhaust gas. We have studied a combined SC (Superconducting Coil) type linear generator as the most realistic system. The linear generator system has improved to increase output, power factor and measuring equipment. In this paper, the linear generator system is experimented in running tests on the Yamanashi Test line. We can supply power of 25kW to half a car in the speed range 400km/h to 500km/h. A good correlation is recognized between the analysis and measurement in the running tests. This linear generator system can be expected to be applicable in the practical use

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This paper presents a novel type electric kiln which fires the pottery using the decompression. The electric kiln is suitable for the environment and the energy saving as the pottery furnace. This paper described the baking principle and the baking characteristic of the novel type electric kiln.

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This paper presents a novel type of 3-level 3-phase 3-switch type voltage-fed soft-switching PWM AC/DC Converter with new Active Auxiliary Resonant Commutated Snubber topology which can operate under a condition of Zero Voltage Switching. The operating performances of the proposed three phase soft-switching PWM rectifier which is more suitable for power systems applications is evaluated on the basis of Simulation results.

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In this work, the authors suggest the use of numerical optimization for on-line adjustment of the exciting period in electronic damping of a stepping motor. The simplex method, which consists of some simple procedures only, is adopted as the optimization technique. In the process of adjustment, a speed sensor is used instead of a position sensor, because of its cheapness. The suggested method is applied to adjustment of the backphasing damping method, and the effectiveness is confirmed

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This IGBT switch consists of 100 IGBT elements connected in series and each rating is 1700 V, 400 A. This paper reports the test results of 1kHz, 50 A, 100 kV switching and 420 A short circuit breaking. The successful results of it indicates the promising view as the modulator for a gyrotron or a klystron that the output is higher than 1 MW.

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In this paper, we propose a new strict model of stepping motors based on the Lawrenson's model. Current offsets and a crrent amplitude ratio are newly introduced and the vibration phenomenon can be expressed by using the model. The validity of the model is examined through simulations and experiments.

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