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This paper presents a current control design for switched reluctance motors (SRMs). The electric transfer characteristic of the motors is studied first. Their transfer function is shown to be expressible by a pure resistive component, which is not constant but varies depending on the motor current and speed. The current control design for SRMs follows the classical design technique used for DC machines, where the zeros of the PI controller cancel the poles of Ls+R. Because the transfer function of SRMs does not have any poles, an I controller is suitable for them. The integral gain should be adjusted in order to compensate the nonlinearity, that is, the variation in the equivalent resistor of the SRMs' transfer function. The values of the integral gain are tuned and tabulated for the motor speed and current. Simulation and experiment demonstrate that the current and speed of the SRMs present good responses without dependence on the motor speed and current. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 173(1): 51–59, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20987 [ABSTRACT FROM AUTHOR]

A 3D boundary integral equation is applied to a model of a short-primary linear reluctance motor. The model is a double-sided construction where the primary member is surrounded by a set of secondary iron plates on both sides. Six kinds of different secondary geometries are calculated and their characteristics are discussed. For the confirmation of calculation results, a test machine is manufactured. Test results are compared with calculated ones. Furthermore, the static thrusts of a single-sided machine and a coreless PMLSM are measured and compared with those of the double-sided machine. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(1): 58–65, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20390 [ABSTRACT FROM AUTHOR]

In this paper, sensorless control for synchronous reluctance motors (SynRMs) without signal injection and an inductance measurement for position estimation are proposed. In the case of SynRMs, accuracy of inductances is the most important factor in realizing precise position estimation because inductances are largely varied by a magnetic saturation phenomenon. Therefore, the inductance measurement method, which can measure appropriate inductances for position estimation, is important as well as a sensorless control method. The inductance measurement based on the observer is discussed, and the measurement method and the parameter adjustment method for improved stability of the closed loop are proposed. The proposed method can measure inductances easily and be applied for permanent magnet synchronous motors, too. Finally, the proposed sensorless control method is verified experimentally. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(4): 70– 80, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ eej.20274 [ABSTRACT FROM AUTHOR]

This paper presents a new characteristics analysis of a dynamic mathematical model for synchronous reluctance motors, which is recently attracting attention in conjunction with the problem of rotor phase selection and estimated based on the extended BEMF (back electromotive force) for sensorless drive. This paper gives the following new characteristic results in a simple unified analytical manner. (1) Change between positive and negative salient pole phases requires basically no modification to the dynamic mathematical model in the general reference frame. (2) Selection of positive or negative salient pole phase as rotor is no more than a preference of designers. (3) There exists a very simple method of deriving two stator flux models for explicit expression of the extended BEMF. (4) At least four circuit equations with the extended BEMF exist, which are equivalent to each other on the same reference frame. (5) There exists duality among the four circuit equations from the viewpoints of rotor phase selection. (6) The duality reinforces the above-mentioned five results. Main results of this paper correct or reinforce the results recently reported by others. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(1): 69–75, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20244 [ABSTRACT FROM AUTHOR]

The d-axis inductance of reluctance motor is affected by not only the d-axis current but also the q-axis current, because of cross magnetic saturation between the direct and quadrature axes. This situation is similar for the q-axis inductance. The authors propose a method to determine the d-axis inductance related to the d- and q-axis currents and the q-axis inductance related to the d- and q-axis currents from a standstill test. This method involves the following four steps. First a rectangular-wave voltage, alternated between plus and minus, is applied to the two armature winding terminals after breaking the rotor in the d-axis position. Secondly, the voltage and current between the terminals are measured. Thirdly, the d-axis inductance related with d-axis current is calculated from the voltage and current. Finally, the process above is repeated when a DC current flows from the remaining armature terminal to neutral point terminal and the d-inductance related to the d- and q-axis currents is derived. A similar treatment applies when determining the q-axis inductance related to the d- and q-axis currents in the q-axis rotor position. The method is implemented on a 1.1 kW–178 V–6.3 A-4P–2200 min-1 flux barrier type reluctance motor. Results of load performance on a vector controlled reluctance motor measured by on-load tests and calculated from the d- and q-axis inductances obtained by the proposed method clearly demonstrate the validity of the proposed method. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 149(4): 52–59, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10377 [ABSTRACT FROM AUTHOR]

In this paper, we propose a new hybrid-type switched reluctance motor (SRM) with salient pole stator, which has a pair of permanent magnets attached symmetrically between the iron poles of the rotor. We describe experimental results not only on the basic characteristics of the hybrid SRM, but also characteristics with a current control loop under optimized advanced firing angle and cutoff angle control. Considerable improvement of machine performance, especially in the efficiency and power factor, for the hybrid SRM over the conventional VR-type SRM is confirmed. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 147(3): 72–79, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10285 [ABSTRACT FROM AUTHOR]

The switched reluctance motor (SRM) exhibits desirable features including simple construction, high reliability, and low cost. However, the SRM has not been put into practical applications widely because of its large torque ripple, acoustic noise, and low power factor. Furthermore, the quantitative analysis and optimum design of the SRM have not been clarified thoroughly. In this paper, the authors propose one method for calculating the operating characteristics of the SRM based on SPICE, the general-purpose circuit simulation program. The calculated results obtained in the trial 8/6 SRM show good agreement with the experimental ones. The method is useful for optimum design of the SRM. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 142(1): 50–56, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ eej.10092 [ABSTRACT FROM AUTHOR]

High-performance drive of synchronous motors such as a permanent magnet synchronous motor and a synchronous reluctance motor can be achieved by current vector control. In such drive systems, the armature current is controlled as a sinusoidal waveform based on rotor position information from a high-resolution position sensor, and the current vector (d- and q-axis currents) is suitably controlled by current feedback control. This paper proposes a current sensorless drive system with a low-resolution position sensor in order to simplify the SM drive system. High-performance current control is achieved in the proposed drive system, where the current sensors are eliminated and the simulated currents are used for current control. The low-resolution position sensor is used instead of a conventional high-resolution position sensor, and the higher position information is estimated. The steady-state and transient characteristics are examined in several experiments with respect to the synchronous reluctance motor and the interior permanent magnet synchronous motor. It is confirmed that sinusoidal current drive, high-performance current vector control, and speed control can be achieved by the proposed drive system. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(4): 34–43, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10072 [ABSTRACT FROM AUTHOR]

This paper reports an IPMSM rotor configuration with a concentrated-winding stator. The inductance of the concentrated winding is greater than that of the distributed winding and the flux density of the concentrated winding contains higher harmonic components. The result is higher winding losses than in the IPMSM with a distributed-winding stator. We discuss three types of interior magnetic rotor with different saliency ratios. In the lower speed range, the highest-saliency rotor is effective in decreasing the load current and copper losses. On the other hand, in the higher speed range, the higher-saliency rotors result in greater iron losses and lower motor efficiency; in this range, the lower-saliency rotor is effective in decreasing iron losses and increasing motor efficiency. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 139(4): 71–78, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10005 [ABSTRACT FROM AUTHOR]

In this paper, a mathematical model of the synchronous reluctance motor in a new form is established, followed by a new analysis of stator linkage flux of the motor, which characterizes the motor and plays an essential role in developing new rotor salient-pole orientation methods for sensorless vector controls. Finally in a unified manner based on the inherent characteristics of the flux, six new potential salient-pole orientation methods are developed and proposed. © 2002 Scripta Technica, Electr Eng Jpn, 139(2): 61–71, 2002;DOI 10.1002/eej.1153 [ABSTRACT FROM AUTHOR]

A synchronous reluctance motor has many advantages because it has no permanent magnet, such as low back emf in high-speed operation, maintaining performance in a high-temperature environment, and so on. Therefore, many rotor constructions have been studied and developed. The rotor with multiflux barrier structure has the merit of easy construction and high performance. The linear synchronous reluctance motor has been developed. It is necessary to improve the performance of the mover design for industrial use, because of its low power factor. In this paper, we propose a novel configuration of mover for the linear synchronous reluctance motor, and examine the static characteristics of the motor with reluctance equalization design by means of the finite element method. From analytical results, it is demonstrated that the static characteristics of the linear synchronous reluctance motor are greatly improved by the reluctance equalization design at the iron layer in the mover. © 2002 Scripta Technica, Electr Eng Jpn, 138(4): 61–69, 2002; DOI 10.1002/eej.1139 [ABSTRACT FROM AUTHOR]

Permanent magnet synchronous motors (PMSMs) are widely used in many applications as high-performance variable-speed drives. In traction drives, such as those used for electric vehicles or for the compressor drives of air conditioners, a wide constant-power speed range and high-efficiency operation are desired. The aim of this paper is to develop a high-performance PMSM that offers high-efficiency performance in the high-speed region, including light-load conditions, as well as a wide constant-power speed range. Simulations show that the proposed interior PMSM, which produces chiefly reluctance torque and in which the permanent magnet flux assists torque production, is capable of meeting the above performance requirements. A prototype PMSM is designed in accordance with this new design concept and several drive tests are carried out. The saliency ratio of the prototype IPMSM is about 5, and, as a result, reluctance torque is the principal torque component, representing more than 70% of total torque. The prototype IPMSM can attain a constant-power speed range of up to 5:1 with high-efficiency drive in the high-speed, constant-power region. The proposed IPMSM is suitable for variable-speed drives requiring high-speed, constant-power operation. © 2000 Scripta Technica, Electr Eng Jpn, 134(3): 60–68, 2001 [ABSTRACT FROM AUTHOR]

Compared to the conventional SRM, fully-pitched winding reluctance motors have a higher salient ratio for given motor dimensions. In addition, since the generated torque of the motor is determined as the product of the rate of change of mutual inductance with respect to a rotor position and winding current amplitude of the corresponding two phases, the motor is suitable for the bipolar current drives. Accordingly, the conventional general-purpose inverter drive of the fully-pitched winding reluctance motor is possible. In this case, the optimum lead angles of voltage play an important role in obtaining the maximum torque and maximum torque/current ratio operations. In this paper, a scheme for determining the optimum angles of voltage without any measurement, and a method for evaluating the drive characteristics in the design stage are proposed by a combination of simple magnetic and electrical analysis. The effectiveness of the proposed analytical scheme is verified by an experiment using a 400-W prototype fully-pitched winding reluctance motor. © 2000 Scripta Technica, Electr Eng Jpn 134(1): 45–52, 2001 [ABSTRACT FROM AUTHOR]

Although the reluctance motors are attractive from the standpoints of simple construction and drive electronics, the relatively high torque ripple and acoustic noise are major drawbacks. These drawbacks limit motor applications. In this paper, the torque ripple suppression of the reluctance motor under the sinusoidal current drive is examined. The analysis shows that the torque ripple is caused by the spatial harmonics of inductance. One approach is based on the compensation current generated with the spatial harmonics of inductance. Another is based on the modification of rotor tooth configuration to eliminate the spatial harmonics. According to the proposed strategies, torque ripple suppression characteristics can be evaluated at the design stage of the motor. Both approaches have been verified by experiments. © 1999 Scripta Technica, Electr Eng Jpn, 130(1): 118–128, 2000 [ABSTRACT FROM AUTHOR]

The authors have previously presented a control scheme for synchronous reluctance motors in which the motor current is controlled to keep the MMF (magnetomotive force) phase angle constant, and have shown that a simpler control scheme is possible by using an N-speed synchro for a 2N pole motor. However, conventional brushless synchros are expensive and bulky due to the intricate construction, where a rotary transformer supplies current to the exciting winding on the rotor core. The authors have therefore developed a novel VR (variable reluctance) synchro without the rotary transformer. This paper describes the theory of the novel VR synchro and presents measured waveforms of the output voltages of a prototype VR four-speed synchro. In addition, a variable speed drive system for eight-pole reluctance motors which uses the new control scheme is introduced. In this system, the VR synchro is directly connected to the motor shaft, whose output voltages are demodulated and directly used as the current phase command for the inverter current supplied to the motor. Experimental results show a satisfactory speed response for four-quadrant drive. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(3): 54–63, 1997 [ABSTRACT FROM AUTHOR]

The authors and others developed a 15 kW revolving-armature type commutatorless motor deriving high magnetic loading. The commutatorless motor was first manufactured with interpole and compensating windings having a construction allowing easy installation and removal of interpoles. It was found from this experiment that this motor was improved in overload torque and the effect of interpoles did not affect compensating windings of the spare angle improvement. Therefore, the compound commutatorless motor (with compensating windings) was manufactured as an experiment. A high output of 190% power was derived by this motor and compensating windings were not needed. By characteristics analysis and simulation, the main factor by which this high output was obtained was that the leakage reactance Xl of this motor was half that of old commutatorless motors. This paper reports this effect, including the experimental data. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(2): 82–95, 1997 [ABSTRACT FROM AUTHOR]