The additional harmonic losses in induction motors driven by PWM inverters are investigated from both results of experiments and finite element methods. Both the experimental and calculated results show that the total additional motor loss decreases with an increase in switching frequency, whereas it does not depend on load conditions. On the other hand, the finite element methods reveal the variation in each loss component with switching frequency, load conditions, and rotor-slot shapes. It is clarified that the components of additional motor loss considerably varies with these factors. In the closed rotor slot motor, the harmonic core losses decrease whereas the harmonic secondary cage losses increase with load. On the other hand, in the semi-closed slot motor, the ratios of these components are not considerably changed with load. This difference is mainly caused by the variation in magnetic saturation and skin effect at the rotor bridges of closed slot motor.
Brushless excitation synchronous generators have been widely used because of their ease of operation and maintenance. Until now, in the analyses of transient phenomena, the brushless AC exciter and the permanent magnet generator (PMG) have been conventionally considered to be modeled transfer functions. In this paper, a new model for the brushless synchronous generator is proposed that can simulate the transient phenomena in the field circuit more accurately. The authors verified the model by comparison with the actual measurement of the excitation response of a 400MVA-class turbogenerator with brushless excitation.
This paper presents a method for optimizing the efficiency of a surface permanent magnet (SPM) motor taking into account the carrier harmonics based on magnetic and electric networks. The eddy current loss in the magnets of the SPM motor, including carrier harmonics, is calculated with an electric network model. Then, an efficiency map of the SPM is created by using the proposed electric and magnetic network models to evaluate the motor efficiency. Finally, the efficiency of the SPM motor is optimized by changing the stator structure.
This paper proposes a rotor damper as a device to reduce the rotor loss. The rotor damper is a thin copper plate inserted between the magnets and the rotor shaft. The eddy current in this damper can suppress the flux harmonics with minimum rotor loss. Both analytical estimation and numerical simulation are performed. The experimental results show that the technique is effective and practical.
This paper proposes a new control algorithm to reduce the capacity of the previously proposed smart charger for electric vehicles (EVs) on single-phase three-wire distribution feeders using reactive power control on the source side. The basic principle of the proposed reactive power control algorithm is discussed in detail. It is shown that controlling the reactive power on the source side reduces the capacity of the previously proposed smart charger. A digital computer simulation is carried out to confirm the validity of the proposed control algorithm using PSIM software. A prototype experimental model is constructed and tested. The experimental results demonstrate that balanced source currents with a power factor of 0.9, which conforms to Japanese regulations, are obtained on the secondary side of the pole-mounted distribution transformer during both the battery charging and discharging operations in EVs reducing the capacity of the smart charger by 31% in comparison to that of the smart charger with the previously proposed control algorithm.
The purpose of the present paper is to analyze the input inductor design and to establish the relationship between the capacitance of the flying capacitor and the output voltage ripple in order to reduce the size and weight of the flying capacitor DC-DC boost converter (FCBC). The inductance of the input inductor is designed by considering the maximum input current ripple, and the experimental results are used to confirm that the input current ripple is within the designed value. Furthermore, according to the design specifications, the required inductance of an input inductor is approximately 25% of that of a conventional two-level DC-DC boost converter, and the required inductor core volume is approximately 35% of that of a conventional two-level DC-DC boost converter. Moreover, the capacitance of the flying capacitor and the output voltage ripple are confirmed to be independent of each other. Theoretically, this is because the time constant of the output capacitance and the output resistance of the FCBC is larger than the switching period of the switching frequency. This finding is confirmed by the simulation and experimental results of the present study. On the basis of this finding, the capacitance of the flying capacitor can be estimated and designed without considering the output voltage ripple. Moreover, the achieved maximum efficiency of the designed FCBC is 98.5% of the output power at 1kW.
High-precision stages are industrial equipment used in micro-fabrications. Fast and precise positioning control is a very important technology for improving the throughput and the product quality. In particular, a large-scale stage has a low resonance mode which disturbs fast and precise positioning because of the structures of the stage. In this paper, a novel feedback system is proposed in a SIMO system using multiple position sensors which are located at an actuator side and a load side. The proposed feedback system has two remarkable features. One is that the effect of the vibration suppression and the phase stabilization of the resonance mode can be tuned simultaneously with only two parameters. The other is that the tuning of the resonance mode does not affect the rigid mode at all. Finally, simulations and experiments with an XY-gantry-stage are performed to demonstrate the advantages of the proposed feedback control system.
This paper proposes a design method for stepped skewing of rotor magnets to selectively eliminate the harmonics of the no-load electromotive force (EMF) and the ripple torque, which is generated by the interaction of the stator current magnetomotive force with the rotor magnet flux distribution. The method is based on the theory that a harmonic component of the ripple torque is generated by the corresponding two harmonics of the no-load EMF. An elementary unit of the proposed skewing for canceling out one harmonic EMF consists of two identical magnet blocks skewed axially. For suppressing a harmonic ripple torque, the corresponding two harmonic EMFs are canceled out by skewing two identical elementary units or a four-step skewing. In the paper, the skew angle for canceling out each harmonic EMF is theoretically obtained. It is shown that one harmonic ripple torque is almost completely suppressed by the proposed four-step skewing through two-dimensional and three-dimensional finite element method (FEM) analyses. In addition, experiments are performed to confirm the selective elimination of one harmonic EMF and to validate the FEM analyses. By using the proposed method, a multiple-step skewing can be designed to simultaneously suppress more than one harmonic component of the ripple torque.