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Synchronous reluctance motors (SynRMs) with four layers of flux barriers are currently in practical use as high-efficiency motors for industrial applications. While SynRMs have higher efficiency than induction motors, they have a high torque ripple. In this study, an asymmetric rotor structure was designed to reduce the torque ripple of the four-layer SynRM, considering the mechanical strength. Two rotor structures with different flux barrier angles were combined in the stacking direction, and the ratio of the combination was optimized by finite element analysis. In addition, prototypes of the initial structure and proposed asymmetric structure were manufactured, and their torque and efficiency characteristics were measured. The experimental results show that the proposed asymmetric structure can reduce the torque ripple while maintaining the basic characteristics such as average torque and efficiency. [ABSTRACT FROM AUTHOR]

A sensorless-control technique for improving the performance of interior permanent-magnet synchronous-motor control such as the operating speed range and position estimation accuracy is proposed herein. The method presented is based on the estimation of an extended electromotive force in a rotating reference frame. The difference between the reference voltage and the actual voltage of the inverter is modeled and compensated for in order to improve the accuracy and the stability of the sensorless drive system. Moreover, an online parameter-identification technique is applied in order to improve the accuracy of position estimation. The effects of the proposed scheme are evaluated by the experimental results. Index Terms--Interior permanent-magnet synchronous motors (IPMSMs), online parameter identification, sensorless control, voltage error compensation.

The influence of rotor configuration on sensorless control for interior permanent-magnet synchronous motors (IPMSM) with concentrated windings is evaluated. Sensorless control that gives estimated angle with simple integration procedure and the biased convergent point observer is applied. Two types of rotors are analyzed and their robustness for an offset value of the observer is compared. To analyze the influence of magnetic saturation, nonlinear motor voltage equation is solved. Finite-element analysis plays an important role to realize high-speed and precise analysis. Analyzed results show that the rotor which has salient poles on the side of permanent magnets is insensitive to the offset value of the observer. And the sensitivity to the offset value of the observer with these two types of rotors is confirmed by experimental results. Index Terms--Concentrated windings, finite-element method, interior permanent-magnet synchronous motors (IPMSM), magnetic saturation, sensorless control.

This paper proposes a variable-speed wind generation system using an interior permanent-magnet synchronous generator (IPMSG). The armature current vector of the IPMSG is optimally controlled according to the generator speed in order to maximize the generated power from the wind turbine. The IPMSG is controlled by the loss-minimization control with maximum power point tracking below the base speed, which corresponds to low and medium wind speed, and the maximum energy can be captured from the wind. Above the base speed corresponding to the high wind speed region, the current- and voltage-limited maximum output control is applied, where the current vector is optimally controlled so that the output may become the maximum in consideration of the constraints of current and voltage. The proposed output maximization control is achieved without mechanical sensors such as wind speed sensor and position sensor. The control system has been developed and several experimental results show the effectiveness of the proposed wind generation system. Index Terms--Interior permanent-magnet synchronous generator (IPMSG), maximum power point tracking (MPPT) control, sensorless control, variable-speed generation, wind generation.

An interior permanent-magnet synchronous motor (IPMSM) is a highly efficient motor and operates in a wide speed range; therefore, it is used in many industrial and home appliance applications. However, the torque ripple of synchronous motors such as the IPMSM and synchronous reluctance motor is very large. The variation of magnetic resistance between the flux barriers and teeth causes the torque ripple. In this paper, flux barriers are asymmetrically designed so that the relative positions between the outer edges of the flux barriers and the teeth do not correspond. As a result, torque ripple can be reduced dramatically. Index Terms--Asymmetric flux barrier, permanent-magnet synchronous motor, synchronous reluctance motor (SynRM).

Iron loss prediction is an important issue in both design and analysis of electrical machines. Because of their complicated structure, flux distribution, and rotational variation of flux, it is difficult to predict the iron loss in a machine exactly. This paper studies the iron loss in the core of rotating machines in which the rotational field is dominant, using the finite-element method. For electrical machines in practical operation, additional iron losses due to the appearance of rotation of flux vectors and harmonic flux densities make the calculation results deviate from the measured data. We have revised the method to account for these excess iron losses by considering both the influences of flux vector rotations and flux density harmonics. Calculation and experiments on two kinds of interior permanent-magnet synchronous motors have verified that our method produces results that agree well with the experimental ones. Index Terms--Electric machines and transformers, magnetic losses.

This paper proposes the current-sensorless drive system with only low-resolution position sensor in order to simplify the synchronous motor drive system. The high-performance current vector control can be achieved in the proposed drive system, where the current sensors are eliminated but the simulated currents based on motor model are used for current control. The low-resolution position sensor, which has a resolution of only 60 electrical degrees, is used instead of a conventional high-resolution position sensor, and the position information with higher resolution is estimated. The steady-state performance and dynamic performance are examined by several drive tests with respect to the interior permanent-magnet synchronous motor and the synchronous reluctance motor. The effectiveness of the proposed drive system is clarified from several experimental results. Index Terms--Current-sensorless drive, low-resolution position sensor, permanent-magnet synchronous motor (PMSM), synchronous reluctance motor (SynRM), vector control.

This paper presents a novel sensorless control strategy for a salient-pole permanent-magnet synchronous motor (PMSM). A new model of a salient-pole PMSM using an extended electromotive force (EMF) in the rotating reference frame is utilized to estimate both position and speed. The extended EMF is estimated by a least-order observer, and the estimation position error is obtained from the extended EMF. Both estimated position and speed are corrected so that the position error becomes zero. The proposed system is very simple and the design procedure is easy and clear. Several experimental drive tests are demonstrated and the experimental results show the effectiveness of the proposed sensorless control system. Index Terms--Extended electromotive force, interior permanent-magnet synchronous motor, observer, salient-pole permanent-magnet synchronous motor, sensorless control.

Permanent magnet linear synchronous motors have been developed for factory automation, transportation applications, and so on. In the rotary-type permanent magnet synchronous machines, the wide speed and constant power operation are realized by using the reluctance torque due to the saliency and the flux-weakening control. In this paper, we examine the effect of the interior permanent magnet arrangement for wide speed operation and the end effect in the linear structure. Index Terms - End effect, flux weakening, IPM-LSM, reluctance thrust.

Permanent magnet synchronous (PM) motors can be applied to applications requiring constant power operation, such as traction and spindle drives by means of flux-weakening control. In a PM motor drive system with flux-weakening control, the motor parameters are used to produce the current vector command. The motor parameters vary because of magnetic saturation and as a result, the control performances are affected by the magnetic saturation. In this paper, the effects of magnetic saturation are examined and the control system considering the magnetic saturation is proposed. The performances of the proposed control system are examined by simulations and the experimental results with respect to the prototype interior permanent magnet synchronous motor.

Interior permanent magnet synchronous motors can be applied to applications requiring wide-speed operation. The current vector control algorithm of an interior permanent magnet synchronous (IPM) motor for constant power operation over the base speed is proposed. As the available voltage controlling the armature current vector is small in the flux-weakening constant power region, the current vector sometimes becomes uncontrollable in transient operations because of the current regulator saturation. The high-performance current regulator is also proposed to improve the current responses in the flux-weakening region, which includes the decoupling current controller and the voltage command compensator. The control performances are confirmed by several drive tests with respect to the prototype IPM motor.

The advantages of the conventional cylindrical linear pulse motor (C-LPM), which has a ring permanent magnet between the A- and B-phase stators, are its simple magnet shape and small motor diameter; the disadvantages are the thrust imbalance resulting from the magnetic flux path of the outer poles being longer than that of the inner poles. This thrust imbalance decreases the pull-in thrust and increases the positioning error. In this paper a new C-LPM with an interior permanent magnet mover which reduces this thrust imbalance is proposed. Steady and dynamic thrust are also examined and magnetic equivalent circuit is discussed. It is shown that a C-LPM with an interior permanent magnet mover effectively improves the thrust imbalance and the dynamic thrust.

This paper examines the design and the performances of a permanent-magnet assisted synchronous reluctance motor (PMASRM) for wide constant-power operation. The effects of properly adding magnets into the rotor of a synchronous reluctance motor are examined by several experimental results and analyses on the prototype machines. The proposed machine can offer a large constant-power speed range, high-efficiency and high-power-factor operation in comparison to the complete synchronous reluctance motor. It was shown that the problems such as the decrease of efficiency at light-loads and the uncontrolled generator mode operation, which occur in the high-speed flux-weakening operation of the conventional PM motor drives, can be eliminated in the PM-assisted synchronous reluctance motor. Index Terms--Constant-power operation, high efficiency, permanent-magnet-assisted synchronous reluctance motor, reluctance motor.

Interior permanent magnet synchronous motors (IPMSMs) are often used in applications that demand high performance. Interest has increased in designing IPMSMs in the enlargement high-efficiency operation area. Designing to meet such specifications can be difficult and time consuming. Combining a genetic algorithm (GA) with the coarse mesh finite element method (FEM) can automate the process and reduce the time it takes to design an IPMSM to meet such specifications. This study describes the motor design and explores the usefulness of designing motors having the large high-efficiency operation area using the GA combined with the coarse-mesh FEM. [ABSTRACT FROM AUTHOR]

When direct torque control (DTC) is applied to permanent-magnet synchronous motor (PMSM) drives, the relationship between the torque and stator flux linkage is important for high-efficiency drives because DTC requires them as references. In the stator flux linkage synchronous frame (M–T frame), the torque is described by a simple equation using the T-axis current. However, the M-axis current is neglected in the equation. This paper derives the relationship between the M-axis current and the stator flux linkage, and proposes a maximum torque per ampere (MTPA) control strategy for direct torque controlled PMSM drives using the above relationship. The proposed method does not require the q-axis inductance, which often varies due to the magnetic saturation. The simulation and experimental results verify that the MTPA condition can be obtained with the proposed method. [ABSTRACT FROM AUTHOR]

This paper proposes a maximum torque per ampere control strategy for direct-torque-controlled interior permanent magnet synchronous motor drives. The proposed method is based on the solutions of a quartic equation, a motor model in the d-q rotating frame often used for the synchronous motor controllers, and a well-known equation for maximum torque per ampere control. Therefore, the proposed method does not use a lookup table that depends on parameters of the motor and that has to be created in advance. In addition, the proposed method can use the estimated parameters. Particularly, the variations of the d- and q-axes inductances can be estimated when the inductances are modeled as the functions of the d- and q-axes current. The simulation results validate that the proposed method can achieve the maximum torque per ampere control. In addition, the simulation and experimental results verify the accuracy improvement of the maximum torque per ampere control with the iterated calculation. [ABSTRACT FROM AUTHOR]

This paper proposes a novel method of using maximum torque per ampere (MTPA) control for direct torque control (DTC) of a permanent-magnet synchronous motor (PMSM) in the stator flux linkage synchronous (M-T) frame. The stator flux vector estimation of DTC enables use of the M-T frame. Consideration of the magnetic saturation and cross-coupling effects in PMSMs requires significant complexity in most of the mathematical models using the rotor synchronous ($d-q$) frame. In the M-T frame, the mathematical model for MTPA control requires only three parameters that can be determined from only three measured points. The validity of the proposed method is confirmed by experimental results. [ABSTRACT FROM AUTHOR]

A mathematical model is proposed for the maximum torque per ampere (MTPA) control law of a permanent-magnet synchronous motor (PMSM) in the stator flux linkage synchronous frame (M-T frame). The mathematical model takes into consideration magnetic saturation and cross-magnetization effects. In taking into consideration magnetic saturation effects, most of the mathematical models in the d\mbox-q frame are complex. The M-T frame has several advantages, such as the simplicity of the flux-weakening control law and its applicability to various motors. In this paper, the control characteristics of a PMSM in the M-T frame are analyzed, and a mathematical model for estimating the MTPA control trajectory in the M-T frame is proposed. In addition, a method of simply determining the parameters for the mathematical model is proposed. The validity of the proposed model is confirmed by comparing the analytical and experimental results. [ABSTRACT FROM PUBLISHER]

Permanent-magnet (PM) synchronous motor (PMSM) with rare-earth PMs is most popular for automotive applications because of its excellent performance such as high power density, high torque density, and high efficiency. However, the rare-earth PMs have problems such as high cost and limited supply of rare-earth material. Therefore, the electric motors with less or no rare-earth PMs are required in electric vehicle (EV) and hybrid electric vehicle (HEV) applications. This paper proposes and examines a PM-assisted synchronous reluctance motor (PMASynRM) with ferrite magnets that has competitive power density and efficiency of the rare-earth PMSM employed in HEV. The PMASynRM for automotive applications is designed taking into account the irreversible demagnetization of ferrite magnets and the mechanical strength. The prototype PMASynRM has been manufactured, and several performances such as torque, output power, losses, and efficiency are evaluated. Furthermore, the performances of the high-power PMASynRM are estimated based on the experimental results of the prototype PMASynRM, and the possibility of the application of the proposed PMASynRM to EV and HEV is discussed. [ABSTRACT FROM PUBLISHER]

Although motors that use rare-earth permanent magnets typically exhibit high performance, their cost is high, and there are concerns about the stability of the raw material supply. This paper proposes a permanent-magnet-assisted synchronous reluctance motor (PMASynRM) with a ferrite magnet that does not use rare-earth materials considering productivity. The performance of the proposed PMASynRM is evaluated based on the finite-element method and an experiment using a prototype machine. The analysis results reveal that the proposed PMASynRM has the same power density and an equivalent efficiency as rare-earth permanent-magnet synchronous motors for hybrid electric vehicles (2003 Toyota Prius). Furthermore, some experimental results are presented in order to validate the analytical results. As a result, the proposed PMASynRM was found to achieve high-power-density and high-efficiency performance. [ABSTRACT FROM AUTHOR]

SUMMARY Recently, the use of permanent magnet (PM) motors has risen markedly because of improvements in the performance of rare earth PM motors. However, the use of rare earth materials, which is an important aspect of the high-performance PM motor, should be reduced because of the high cost and unpredictability associated with procuring such materials. The performance of motors that use rare earth materials has reached a very high level, one that will not be easy to match without such materials. In this paper, we propose a structure for a high-power-density PM-assisted synchronous reluctance motor involving the use of a ferrite PM. The structure prevents irreversible demagnetization of the PM even in the presence of heavy flux-weakening excitation or an inverter fault. It is shown that the proposed structure achieves high-power and high-efficiency performance. © 2014 Wiley Periodicals, Inc. Electr Eng Jpn, 187(1): 42-50, 2014; Published online in Wiley Online Library (). DOI 10.1002/eej.22362 [ABSTRACT FROM AUTHOR]

Although motors that use rare-earth permanent magnets (PMs) typically exhibit high performance, high costs and concerns about the stability of raw material supplies are leading to their decreased production. However, the performance of such motors is not easily matched without the use of rare-earth PMs. This paper proposes and examines a PM-assisted synchronous reluctance motor with ferrite magnets that has the same power density as rare-earth PM synchronous motors. A suitable rotor structure for high torque and high power is discussed with respect to the demagnetization of ferrite magnets and the mechanical strength. [ABSTRACT FROM PUBLISHER]

In this study, we investigate the torque response of a control system that is based on the direct torque control (DTC) principle for an interior permanent magnet synchronous motor (IPMSM). We also propose a gain-scheduling method for improving the torque response. Reference flux vector calculation (RFVC) DTC is used in this study. In RFVC DTC, a PI controller is used for torque control; this is in contrast to the use of the hysteresis comparator and switching table in basic DTC. In this paper, we present the relationship between the torque response and the gain of the PI controller. This relationship is derived by using the transfer function of the torque control loop. We also examine the difference between the torque responses of two motors that have different machine parameters. The proposed method can be used to realize a torque response that is independent of the operating torque. The simulation results and experimental results presented in this paper show the validity of the derived relationship as well as the effectiveness of the proposed method. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 181(2): 55-65, 2012; Published online in Wiley Online Library (). DOI 10.1002/eej.21198 [ABSTRACT FROM AUTHOR]

This paper examines the control performance of permanent-magnet synchronous motor drive systems based on current control and direct torque control (DTC) when flux-weakening control is applied. The control law in the M–T frame, which is used in the DTC, requires only armature resistance, whereas the control law in the d–q frame, which is used in current control, requires many motor parameters for flux-weakening control. The experimental results clarify the influence of parameter variation on the control characteristics of flux weakening and torque limiting. The DTC-based motor drive system combined with the control laws in the M–T frame has several advantages, including insensitivity to parameter variation, simplicity of calculation, and stable control. [ABSTRACT FROM AUTHOR]

O6-Methylguanine, one of alkylated DNA bases, is especially mutagenic. Cells containing this lesion are eliminated by induction of apoptosis, associated with the function of mismatch repair (MMR) proteins. A retrovirus-mediated gene-trap mutagenesis was used to isolate new genes related to the induction of apoptosis, triggered by the treatment with an alkylating agent, N-methyl-N-nitrosourea (MNU). This report describes the identification of a novel gene, MAPO2 (O6- methylguanine-induced apoptosis 2), which is originally annotated as C1orf201. The MAPO2 gene is conserved among a wide variety of multicellular organisms and encodes a protein containing characteristic PxPxxY repeats. To elucidate the function of the gene product in the apoptosis pathway, a human cell line derived from HeLa MR cells, in which the MAPO2 gene was stably knocked down by expressing specific miRNA, was constructed. The knockdown cells grew at the same rate as HeLa MR, thus indicating that MAPO2 played no role in the cellular growth. After exposure to MNU, HeLa MR cells and the knockdown cells underwent cell cycle arrest at G2/M phase, however, the production of the sub-G1 population in the knockdown cells was significantly suppressed in comparison to that in HeLa MR cells. Moreover, the activation of BAK and caspase-3, and depolarization of mitochondrial membrane, hallmarks for the induction of apoptosis, were also suppressed in the knockdown cells. These results suggest that the MAPO2 gene product might positively contribute to the induction of apoptosis triggered by O6-methylguanine. [ABSTRACT FROM AUTHOR]

This paper proposes a control method suitable for limited armature voltage and current in a permanent-magnet synchronous motor drive system based on direct torque control (DTC). First, this paper proposes torque-limiting and flux-weakening controls that are suitable for a DTC-based motor drive system. The proposed method utilizes a mathematical model in a rotating reference frame synchronized to the stator flux linkage. Second, this paper proposes an antiwindup scheme for the torque controller of the DTC system. Windup of the controller degrades the performances of torque-limiting (current-limiting) control and of torque control. Applying the antiwindup results improves the performance of the proposed torque-limiting method in the transient state. This paper presents a DTC-based drive system combined with a speed controller. The proposed system can achieve stable control, and its effectiveness is confirmed experimentally. [ABSTRACT FROM PUBLISHER]

The importance of reducing the amount of rare earth materials used in high-performance permanent magnets has been established. However, the performance of such motors will not be easy to match without the use of rare earth materials. Although the torque characteristic of the motor can be improved by shortening the air gap length of the motor, there is a mechanical limitation on the gap length. In this paper, a 3-D air gap structure of the motor is proposed to improve the torque characteristics without shortening the gap length. The 3-D air gap structure is demonstrated to be equivalent to shortening the actual gap length to approximately 70% of the original length. Some disadvantages in the 3-D air gap structure are also described. [ABSTRACT FROM PUBLISHER]

This paper describes an approach in improving the performance of the position sensorless control of an interior permanent-magnet synchronous motor using parameter identification. The model-based sensorless method requires accurate motor parameters. At low speed, the resistance variation degrades the accuracy of position estimation. The identified parameter is used in the sensorless drive system to improve the accuracy of position estimation. In this paper, the resistance is identified online, but the offline identified value of the q-axis inductance is used. The experimental results reveal the effectiveness of applying parameter identification to the sensorless drive system. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel control scheme for maximum power operation of synchronous reluctance motors. The proposed scheme consists of a combination of maximum torque per ampere control, maximum torque per flux control, flux-weakening control, and torque limiting. The first three control methods are based on a mathematical model in a rotating reference frame that is synchronized with the stator flux linkage. The final method utilizes a reactive torque calculated as the inner product of the flux and current vectors. The proposed control scheme is suitable for direct torque control (DTC) or flux-oriented control. In this paper, the scheme is applied to a DTC-based motor-drive system. The validity of the control scheme is verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]

[Purpose] The purpose of this study was to examine the reliability of measurement of a fixed belt which was developed for the measurement of muscle strength of triceps sura with a Hand-Held Dynamometer (HHD). [Subjects] We studied 22 legs of 11 healthy adults for intra-rater reliability, and 20 legs of 10 healthy adults for inter-rater reliability. [Methods] The subjects put their hands posterolateraly in the long sitting position for the measurement of muscle strength of triceps surae. After sufficient practice, isometric foot plantar flexion exercise with the fixed belt was measured and we studied the reliability with the intra-class correlation coefficient (ICC). [Results] The intra-rater reliability was 0.924 (ICC) and the inter-rater reliability was 0.809 (ICC). [Conclusion] It is possible to make objective and reliable measurements which are suitable for clinical use by any measurer. [ABSTRACT FROM AUTHOR]

The model parameters of a permanent magnet synchronous motor (PMSM) are required for high-performance control and a model-based sensorless control. This paper proposes a sensorless control system of PMSM that does not need parametric information beforehand. The parameters of a PMSM drive system, including the inverter, are identified at standstill and under operating conditions. At first, the initial rotor position is estimated by a signal injection sensorless scheme in which the machine parameters are not required. After the initial position has been estimated, the resistance, including the on resistance of the IGBT, the voltage error caused by dead time in the inverter, and d-axis and q-axis inductances, are identified at standstill. After the motor starts by the signal injection sensorless control, the sensorless scheme changes to an extended EMF estimation scheme. The estimated parameters for the resistance, and daxis and q-axis inductances are used in such sensorless control. The magnet flux-linkage, which cannot be estimated at standstill, is identified under the sensorless operation at medium and high speeds. The effectiveness of the proposed method is verified by several experimental results. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(2): 68–76, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ eej.20548 [ABSTRACT FROM AUTHOR]

A mechanical sensorless drive system for an interior permanent-magnet synchronous motor, for which parameters including the inverter are identified, is proposed in this paper. The rotor position is estimated by a signal-injection sensorless scheme at standstill. The resistance, including the on-resistance of the insulated-gate bipolar transistor, the voltage error caused by the dead time of the inverter, and the d-axis and q-axis inductances are identified at standstill using the estimated position. After the motor starts by the signal-injection sensorless control, the sensorless scheme changes to a scheme based on the extended electromotive force estimation, which uses the identified parameters. The magnet flux linkage is also identified under the sensorless operation. The effectiveness of the proposed method is verified by several experimental results. [ABSTRACT FROM AUTHOR]

The influence of permanent-magnetic flux variation and magnetic saturation on sensorless control for interior permanent-magnet synchronous motors with concentrated windings is evaluated. By using finite-element method analysis, partial differential values of flux linkage are calculated directly and precisely in a short time. High-speed analysis of a motor voltage equation is realized by interpolating table data of calculated partial differential values. Analyzed results show good correlation with experimental results. The performance of sensorless control is greatly improved using analyzed results, and the influence of permanent-magnetic flux variation is predicted well. The proposed method is very useful for designing control algorithms, considering the influence of permanent-magnetic flux variation and magnetic saturation. [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]

The article presents information on the use of compensating magnets to reduce thrust imbalance in cylindrical linear pulse motors. A linear pulse motor (LPM) has many advantages for a high accuracy positioning actuator because. It has linear motion without any mechanical link. The flat type LPM generally is used in many industrial applications. However, it has a disadvantage in that the mover support mechanism becomes complex and heavy because the attraction force between the stator and the mover is very large. As the attraction force is balanced in the cylindrical structure, the cylindrical LPM is allowed to have a simple and lightweight support mechanism.

O⁶-Methylguanine, one of alkylated DNA bases, is especially mutagenic. Cells containing this lesion are eliminated by induction of apoptosis, associated with the function of mismatch repair (MMR) proteins. A retrovirus-mediated gene-trap mutagenesis was used to isolate new genes related to the induction of apoptosis, triggered by the treatment with an alkylating agent, N-methyl-N-nitrosourea (MNU). This report describes the identification of a novel gene, MAPO2 (O⁶-methylguanine-induced apoptosis 2), which is originally annotated as C1orf201. The MAPO2 gene is conserved among a wide variety of multicellular organisms and encodes a protein containing characteristic PxPxxY repeats. To elucidate the function of the gene product in the apoptosis pathway, a human cell line derived from HeLa MR cells, in which the MAPO2 gene was stably knocked down by expressing specific miRNA, was constructed. The knockdown cells grew at the same rate as HeLa MR, thus indicating that MAPO2 played no role in the cellular growth. After exposure to MNU, HeLa MR cells and the knockdown cells underwent cell cycle arrest at G₂/M phase, however, the production of the sub-G₁ population in the knockdown cells was significantly suppressed in comparison to that in HeLa MR cells. Moreover, the activation of BAK and caspase-3, and depolarization of mitochondrial membrane, hallmarks for the induction of apoptosis, were also suppressed in the knockdown cells. These results suggest that the MAPO2 gene product might positively contribute to the induction of apoptosis triggered by O⁶-methylguanine.