Tomotsugu Kubota

Steady-state performance analysis of permanent magnet synchronous motors including space harmonics

This paper describes the method for the analysis to obtain steady-state currents and torques of permanent magnet synchronous motors including space harmonics. A time-stepping finite element technique including the rotor movement is proposed, where both terminal voltage and load angle are given as the known values. In simulating the rotor movement, the suitable rotation step to take account of the effects of space harmonics, is determined. The agreement between calculated and measured results of the synchronous performance in an experimental motor is good. >

A novel six-phase inverter system with sixty-step output voltages for high-power motor drives

A novel six-phase voltage-fed inverter system is proposed. The system consists of two main three-phase inverters, coupling reactors, and an additional single-phase inverter. The ripple voltage injected into the DC link by the additional inverter results in 60-step load voltages with the help of the coupling reactors. The main inverters operate at the same frequency as the output and the additional inverter operates at a frequency six times higher. The advantages and disadvantages of the system are quantitatively discussed.

Steady-State and Transient Performance Analysis for a Single-Phase Capacitor-Run Permanent-Magnet Motor With Skewed Rotor Slots

This paper presents a numerical analysis method to accurately predict the steady-state and transient performance of a single-phase capacitor-run permanent-magnet motor with skewed rotor slots. Two-dimensional time-stepping finite-element analysis has been used to successfully predict the steady-state and dynamic transient performance of the prototype motor by using a multislice model. The agreement between computed and measured results of the prototype motor validates the proposed analysis method. The maximum efficiency and minimum torque ripple versus the value of capacitance have been determined from the results of the steady-state synchronous performance analysis. The run-up response corresponding to skew pitch has been obtained from the results of the starting performance analysis.

Hysteresis motor using magnetically anisotropic Fe-Cr-Co magnet

For the rotor ring of the hysteresis motor, semihard Alnico magnets have been almost applied until now. However, the hysteresis motor using Alnico magnets has several disadvantages. In order to improve the disadvantages of conventional hysteresis motors, the Fe-Cr-Co magnet steel with magnetic anisotropy is applied for hysteresis rotor ring. Magnetic anisotropy is used to cause large reluctance torque and large hysteresis torque at synchronous pull out. It is made clear from experimental results that these hysteresis motors have large output, high efficiency, and high power factor, to add the reluctance torque to hysteresis torque effectively.

Voltage-phase shifting effect of three-phase harmonic canceling reactors and their applications to three-level diode rectifiers

For replacing a conventional transformer-coupled system, a novel double rectifier system with 24-step input voltages is proposed for mid-power applications. The system consists of double three-level voltage-type diode rectifiers coupled with three harmonic canceling reactors with a total power capacity of 13.4-18.2% of the DC output power. Additional switches of the unit rectifiers act as forced commutation circuits and the reactors absorb lower harmonics. The proposed system has the advantages over conventional transformer coupled systems of: economical design; small size; light weight; high-quality input currents; and highly reliable operation.

Multilevel current-source and voltage-source converter systems coupled with harmonic canceling reactors

Novel current-source and voltage-source power converter systems with 36-step input waveforms are proposed. Each of the systems consist of two main power converters coupled with harmonic canceling AC-side reactors and an additional converter coupled with DC-side interphase transformers. The additional converter injects into the DC links ripple currents or voltages having a frequency six times that of the line frequencies. The proposed systems are suitable for high power applications because of their low switching frequencies and the low distortion of their waveforms. The system configurations and operations are presented for comparison of the two types. Experimental results show close agreement with theoretical prediction.

Radial flux type hysteresis motor with reaction torque--Numerical analysis of hysteresis motor using finite element method

This paper describes a new form of the radial flux type hysteresis motor having large output, high efficiency, and high power factor. The rotor ring of the machine is made of Fe-Cr-Co magnet steel and has magnetic anisotropy and slits. In order to analyze motor performance at synchronous speed and starting, the finite-element method is used. In this paper, magnetic hysteresis is considered by Using complex permeability. Predicted and measured values of motor performance characteristics agree well. Finally, the relation between dimensional ratio of slits and motor performance is described quantitatively.

A novel control method for single-phase slow switching multilevel rectifiers

A novel control method for single-phase multilevel rectifiers is proposed to meet harmonic current limiting standards with minimum input filter inductance. Since the proposed rectifier consists of a main power circuit of a diode bridge and two auxiliary semiconductor switches in parallel with the main circuit, it provides several features; high efficiencies, high input power factor, and low EMI. The simulation and the experimental results show that the proposed control method reduces the input filter inductance minimum.

Starting performance analysis for a single-phase capacitor-run permanent magnet motor with skewed rotor slots

This paper presents the novel starting performance analysis for a single-phase capacitor-run permanent magnet motor with skewed rotor slots. 2-D time-stepping finite element analysis has been used to successfully predict the starting performance of the prototype motor by using a multislice model. The agreement between computed and measured results of the prototype motor validates the proposed analysis. The run-up response corresponding to skew pitch has been given from the simulation results.

High-Efficiency operation of PWM inverter-driven hysteresis motor with short-duration overexcitation

This paper presents the new scheme for high-efficiency operation of PWM inverter-driven hysteresis motor with short-duration overexcitation. When the terminal voltage Vi of the hysteresis motor running at synchronous speed is continuously increased up to nVi (n≪1) and then continuously decreased to Vi, input currents are reduced and output power is increased at the same time. Because of this, the efficiency becomes high. In this paper, the terminal voltage is controlled by changing the modulation degree of PWM inverter continuously.