A mixed spectral-domain approach for dispersion analysis ofsuspended planar transmission lines with pedestals

A mixed spectral-domain analysis is used to derive dispersion characteristics of domain modes in a class of planar transmission lines with a pedestal. Equivalent structures are constructed in which magnetic surface currents are identified as the unknowns at the aperture separating two different regions. Spectral dyadic Green's functions are derived for these structures using the spectral-domain immittance approach. The characteristic equations resulting from the application of the spectral Galerkin method involve mixing two different spectral domains, which exist on the two sides of the pedestal support. The present method allows one to retain the simplicity and numerical efficiency of the conventional spectral-domain immittance approach, which cannot be applied directly to the present structures. Numerical data are provided for the dispersion characteristics of dominant modes in a pedestal-supported stripline and finline     

Low-harmonic GTO converter for fundamental power factorcompensation

A low-harmonic GTO (gate turn-off) thyristor AC-to-DC converter with line current lead-lag phase shift control ability is proposed and analyzed. The converter can be used either as a low-harmonic GTO-controlled rectifier or a fundamental input power factor compensator in a power supply system. The effect of PWM (pulse width modulation) current phase number on the harmonic contents and converter output voltage control range is investigated. Lower order input current harmonics are eliminated over a wide range, using a specially designed PWM current pattern. The effect of the PWM current pulse number on the power factor compensation characteristic is investigated     

A speed-sensorless vector control method of parallel-connected dual induction motor fed by a single inverter

The purpose of this paper is to present the speed-sensorless vector control method of the torque production from each rotor of two induction motors with parallel-connected stator windings fed by a single inverter. In this paper, an adaptive rotor flux observer is applied to the method in order to eliminate a flux sensor, and an adaptive scheme for rotor speed is added to the adaptive rotor flux observer in order to eliminate a speed sensor. The experimental results show that the proposed method is useful under the condition that the ratings of each induction motor are different.     

A Novel Commutation Method of Matrix Converter Fed Induction Motor Drive Using RB-IGBT

This paper gives an overview of a collector-emitter voltage sign-based commutation method. This method is implemented based on the output current sign and commutation voltage polarity signals of matrix converter. All these signals are acquired by a simple unit in the drive and protection boards designed for reverse blocking insulated gate bipolar transistors (RB-IGBTs) of the matrix converter in test. Therefore, no current and/or voltage sensor is required to obtain any other commutation signals. The RB-IGBT samples used are newly developed, and one important feature is that its reverse leakage current is mostly affected by nu_ge. Under the same temperature condition, when nuce is negative, a positively biased nu_ge results in a distinct decrease of the reverse leakage current. The proposed commutation method can supply the reverse-blocked RB-IGBTs with positively biased nu_ge . Hence, the power losses caused by the reverse leakage current can be reduced using the proposed method. Experimental results have proved the feasibility and effectivity of this method     

The orthogonal CNN problem

The online CNN problem had no known competitive algorithms for a long time. Sitters, Stougie and de Paepe showed that there exists a competitive online algorithm for this problem. However, both their algorithm and analysis are quite complicated, and above all, their upper bound for the competitive ratio is 10⁵. In this paper, we examine why this problem seems so difficult. To this end we introduce a nontrivial restriction, orthogonality, against this problem and show that it decreases the competitive ratio dramatically, down to at most 9.     

Dynamic simulation of the helium refrigerator/liquefier for LHD

A real-time dynamic simulation has been carried out for the 10 kW class helium refrigerator/liquefier of Large Helical Device (LHD) at National Institute for Fusion Science (NIFS). The refrigerator consists of eight screw compressors, seven expansion turbines, fourteen heat exchangers and a 20 m³ liquid helium reservoir. A simulation model was implemented to Cryogenic Process REal-time SimulaTor (C-PREST), developed as a platform for the plant process study and optimization. Validity of the simulation model has been confirmed based on the design values as well as the results of commissioning tests. This paper describes the cooldown process and expansion turbine trips during the operation. Difficulties of dynamic simulation for the large cryoplant are also discussed.     

Deadbeat flux level control of direct-field-orientedhigh-horsepower induction servo motor using adaptive rotor flux observer

A method for the deadbeat flux level control of direct-field-oriented high-power induction servo motor drives has been developed that employs an adaptive rotor flux observer. The observer is a full-order type and is used not only in the direct-field-oriented controller, but also to determine the stator and rotor resistances of the servo motor. The observer reduces the sensitivity of a deadbeat controller to fluctuations in the motor parameters. The main advantage of this method is that it improves the efficiency of an induction servo motor without sacrificing dynamic performance. This paper describes the method as well as the fundamental characteristics of the system derived from experimental and simulation results     

Improved current source GTO inverter-fed induction motor driveswith PWM-controlled thyristor converter

An improved current-source GTO (gate turn-off) inverter system for driving an induction motor at high frequency was developed. This system is composed of an inverter using GTOs and a PWM (pulsewidth-modulated)-controlled thyristor rectifier. The energy rebound circuit in the inverter is used to turn off the thyristors in the rectifier and to apply PWM control techniques. This circuit plays an important role in the treatment of reactive power in a load. The capacitors connected to the AC input terminal to improve PWM control also function as a filter. Thus, the waveforms of the input voltage and current become almost sinusoidal. Principles and circuit operations of the rectifier section are described in detail. The current-source GTO inverter is used to drive a 5.5 kW induction motor. The experimental waveform and characteristics for the tested motor drives are given. It is shown that the harmonic components of the input voltage and current are eliminated or reduced by using the PWM control technique without spoiling the inherent characteristics of the current-source GTO inverter     

Miniaturized planar filters exhibiting flexible placement of three transmission zeros suitable for duplexer design

In this work, we show that a stub‐loaded open‐loop double resonator filter can produce three transmission zeros at finite frequencies close to the passband when designed using our proposed asymmetric feed point topology. We demonstrate that by selecting the length of the stub, the placement of double transmission zeros on either the high side of the passband or the low side of the passband can be selected. This selection can be achieved by using a single design parameter: the stub length. The flexibility in the double zero placement makes these filters particularly advantageous for duplexer designs. Two duplexers are fabricated using the proposed filter topology in a microstrip on a duroid substrate and substrate‐embedded stripline via Low‐Temperature Cofired Ceramic technology (LTCC). The measurements show steep attenuation of approximately 30 dB, close to the filters' passband as well as a compact size down to 0.075λ × 0.17λ.