This paper describes the electromagnetic vibration in magnetic gears. The sources of the electromagnetic vibration are shown, and the components of the vibration are theoretically described. The electromagnetic force that can be detected from cogging torque measurements is verified by employing 3-D finite element method analysis and carrying out measurements on a prototype, and the components that do not appear in the cogging torque measurements are calculated by employing coupled electromagnetic and structural analysis. Finally, these results are also verified through measurements of the sound pressure.
Energy saving in electrical appliances and electric vehicles can be realized by reducing the power consumption of their motors, which operate at variable speeds. In order to reduce reducing the energy consumption of electrical appliances, flux-weakening currents are used to reduce the voltage at high speeds, which leads to significant copper and core losses. To counter this problem, we developed a new technique that changes the number of poles and components of torque production in a permanent magnet (PM) motor based on rotational speed. In this study, we propose a novel motor that changes the poles and torque components, and also explain its principles and basic characteristics. The results of our study show that a PM motor can vary the induced voltage from 53% to 100%, operate a three-torque-production mode through magnetization, and reduce core loss by 21%. Thus, the results of our analysis prove that the proposed motor can change the poles and torque components, and can be utilized to achieve high performance and efficiency in variable speed drive systems.
In this study, we investigate the output maximization of salient-pole synchronous machines by using small amount of Nd-Fe-B magnets. First, the mechanism of output increase by the additional magnets is revealed by using both finite element method and simple magnetic circuit. Then, the appropriate magnet shape and rotor core design are discussed. The experimental verification is carried out by using prototype machines. The advantages of the proposed design are confirmed.
Permanent magnet synchronous motors (PMSMs) have been used in high-performance applications owing to their high efficiency and high power density. In particular, an integrated system of a PMSM and power electronics equipment is attractive for high power density applications because the integrated system is lighter and smaller than the conventional separated system. In this paper, the concept of a new integrated machine named the MATRIX motor is proposed. This motor consists of not only an integrated inverter but also, multi-layer windings and additional switches. These winding connections can be changed arbitrarily on the basis of a matrix. Through winding configurations, variable parameters such as turn number and winding factor can be determined, and the connection method can be changed between series and parallel arrangements. These variable parameters can change motor characteristics such as the maximum output torque, base speed, and operating region. This paper describes the characteristics of a prototype model of the MATRIX motor. The characteristics of the winding rearrangement and its variable machine parameters are analyzed and verified through experiments. In addition, the online winding reconfiguration method is proposed and experimentally verified.
This study investigates the diagnosis of not only broken bar but also broken end ring faults in an induction motor. The difference between the broken bars and broken end ring segments is experimentally clarified by Fourier analysis of the stator current. This difference is verified by two-dimensional finite element (FE) analysis that takes into consideration the voltage equation and the end ring. The electromagnetic field in the undamaged motor and the motor with broken bars and broken end rings is analyzed. Moreover, the effect of the number of broken bars and broken end ring segments on the motor performance is clarified.
This paper proposes two position constrained bilateral controllers. The constraint is given by coordinate transformation and additional compensator or command modification methods are not necessary. The constraint therefore does not destabilize the system and maintains linearity. The difference between the two proposed methods is the task priority. The first ensures slave position limitation and force regulation between two robots, the other ensures position limitation and position regulation between the robots. We analyzed the stability of the proposed controller. The validity of the proposed methods was confirmed experimentally.
This paper describes a formal modeling and verification of an arm pick-and-place system, in which nondeterministic behaviors of the arm state condition and timer function blocks are applied. We design an appropriate PLC program using a ladder diagram (LD) for the arm pick-and-place operation and apply in it a situation where the arm may drop the product or material being gripped because of an external force. In addition, the timer function blocks are used with formalization of their finite-state logical properties. We use an actual model of the arm to verify that safe operations are established for normal product pick-and-place, as well as when the product has fallen. In addition, we perform arm model verifications for five important temporal properties using the NuSMV model checker. We present two types of experiments to validate the safety of the designed LD program. We also verify that the nondeterminism that appears as a result of the system behaviors can be formalized and used to represent logical assumptions for the properties that need to be verified.
This paper proposes a new current vector control method that prevents voltage saturation by regulating the rate of pulse width modulation (PWM) in a flux weakening region according to a reference. While conventional methods use current limiting on both axes (d-axis and q-axis), our method stabilizes the current vector at onset to and within the flux weakening region using only q-axis current signal control. By eliminating the control of the d-axis current, the circuitry of the field programmable gate array (FPGA) is simplified. The effectiveness of the proposed method is verified through experiments of load fluctuations and supply voltage variations.
Multilevel power converters are among the most effective approaches to reduce power loss and to improve efficiency in power conversion systems. Reverse-blocking IGBTs (RB-IGBTs) have been improved and extended to higher breakdown voltage to be used as bidirectional switches in multilevel converter applications. In this work, a hybrid isolation process by combining thermal diffusion and V-Groove etching is developed to form 1200-1700-V RB-IGBTs. The details on 1700-V RB-IGBTs are presented in this paper. Compared with that of full diffusion, the thermal budget of the frontside surface deep boron diffusion has been reduced to less than one-third. Sufficient reverse-blocking capability and switching robustness have been successfully demonstrated. At the same switching loss level, on-state voltage of a 50A-rated planar gate RB-IGBT is reduced to approximately 1.9V compared with that of serially connected trench-gate field-stop IGBT (FS-IGBT) and free-wheeling diode (FWD). Experimental benchmarking on 1200-A module demonstrated that the energy loss in three-level inverter was reduced to 18% by using RB-IGBTs instead of IGBT and FWD pairs at typical switching frequencies for high-power, medium-voltage applications.