VTechWorks Repository :: Browsing by Author "Chen, Dan Y."

Browsing by Author "Chen, Dan Y."

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Advanced High-Frequency Electronic Ballasting Techniques for Gas Discharge Lamps
Tao, Fengfeng (Virginia Tech, 2001-12-19)
Small size, light weight, high efficacy, longer lifetime and controllable output are the main advantages of high-frequency electronic ballasts for gas discharge lamps. However, power line quality and electromagnetic interference (EMI) issues arise when a simple peak rectifying circuit is used. To suppress harmonic currents and improve power factor, input-current-shaping (ICS) or power-factor-correction (PFC) techniques are necessary. This dissertation addresses advanced high-frequency electronic ballasting techniques by using a single-stage PFC approach. The proposed techniques include single-stage boost-derived PFC electronic ballasts with voltage-divider-rectifier front ends, single-stage PFC electronic ballasts with wide range dimming controls, single-stage charge-pump PFC electronic ballasts with lamp voltage feedback, and self-oscillating single-stage PFC electronic ballasts. Single-stage boost-derived PFC electronic ballasts with voltage-divider-rectifier front ends are developed to solve the problem imposed by the high boost conversion ratio required by commonly used boost-derived PFC electronic ballast. Two circuit implementations are proposed, analyzed and verified by experimental results. Due to the interaction between the PFC stage and the inverter stage, extremely high bus-voltage stress may exist during dimming operation. To reduce the bus voltage and achieve a wide-range dimming control, a novel PFC electronic ballast with asymmetrical duty-ratio control is proposed. Experimental results show that wide stable dimming operation is achieved with constant switching frequency. Charge-pump (CP) PFC techniques utilize a high-frequency current source (CS) or voltage source (VS) or both to charge and discharge the so-called charge-pump capacitor in order to achieve PFC. The bulky DCM boost inductor is eliminated so that this family of PFC circuits has the potential for low cost and small size. A family of CPPFC electronic ballasts is investigated. A novel VSCS-CPPFC electronic ballast with lamp-voltage feedback is proposed to reduce the bus-voltage stress. This family of CPPFC electronic ballasts are implemented and evaluated, and verified by experimental results. To further reduce the cost and size, a self-oscillating technique is applied to the CPPFC electronic ballast. Novel winding voltage modulation and current injection concepts are proposed to modulate the switching frequency. Experimental results show that the self-oscillating CS-CPPFC electronic ballast with current injection offers a more cost-effective solution for non-dimming electronic ballast applications.
Advanced Integrated Single-Stage Power Factor Correction Techniques
Zhang, Jindong (Virginia Tech, 2001-03-15)
This dissertation presents the in-depth study and innovative solutions of the advanced integrated single-stage power-factor-correction (S2PFC) techniques, which target at the low- to medium-level power supplies, for wide range of applications, from power adapters and computers to various communication equipment. To limit the undesirable power converter input-current-harmonic's impact on the power line and other electronics equipment, stringent current harmonic regulations such as IEC 61000-3-2 have already been enforced. The S2PFC techniques have been proposed and intensively studied, in order to comply these regulations with minimal additional component count and cost. This dissertation provides a systematic study of the S2PFC input-current-shaping (ICS) mechanism, circuit topology generalization and variation, bulk capacitor voltage stress and switch current stress, converter design and optimization, and evaluation of the state-of-the-art S2PFC techniques with universal-line input. Besides, this presentation also presents the development of novel S2PFC techniques with a voltage-doubler-rectifier front end to both improve the performance and reduce the cost of S2PFC converters for (international voltage range) universal-line applications. The calculation and experimental results show that the proposed techniques offer a more cost-effective and efficient solution than industries' current practice, with universal-line input and converter power level up to 600 W. Finally, further improved technique is also presented with reduced filter inductor size and increased power density.
Advanced Single-Stage Power Factor Correction Techniques
Qian, Jinrong (Virginia Tech, 1997-09-25)
Five new single-stage power factor correction (PFC) techniques are developed for single-phase applications. These converters are: Integrated single-stage PFC converters, voltage source charge pump power factor correction (VS-CPPFC) converters, current source CPPFC converters, combined voltage source current source (VSCS) CPPFC converters, and continuous input current (CIC) CPPFC converters. Integrated single-stage PFC converters are first developed, which combine the PFC converter with a DC/DC converter into a single-stage converter. DC bus voltage stress at light load for the single-stage PFC converters are analyzed. DC bus voltage feedback concept is proposed to reduce the DC bus voltage stress at light load. The principle of operations of proposed converters are presented, implemented and evaluated. The experimental results verify the theoretical analysis. VS-CPPFC technique use a capacitor in series with a high frequency voltage source to achieve the PFC function. In this way, the input inductor is eliminated. VS-CPPFC AC/DC converters are developed, and their performance is evaluated. VS-CPPFC electronic ballasts with and without dimming function are also presented. The average lamp current control with duty ratio modulation is developed so that the lamp operates in constant power with a low crest factor over the line variation. The experimental results verify the CPPFC concept. CS-CPPFC technique employs a capacitor in parallel with a high frequency current source to obtain the PFC function. The unity power factor condition and principle of operation are analyzed. By doing so, the switch has less switching current stress, and deals only with the resonant inductor current. Design considerations and experimental results of the CS-CPPFC electronic ballast are presented. VSCS-CPPFC technique integrates the VS-CPPFC with the CS-CPPFC converters. The circuit derivation, unity power factor condition and design considerations are presented. The developed VSCS-CPPFC converters has constant lamp operation, low crest factor with a high power factor even without any feedback control. CIC-CPPFC technique is developed by inserting a small inductor in series with the line rectifier for the conceptual VS-CPPFC, CS-CPPFC and VSCS-CPPFC circuits. The circuit derivation and its unity power factor condition are discussed. The input current can be designed to be continuous, and a small line input filter can be used. The circulating current in the resonant tank and the switching current stress are minimized. The average lamp current control with switching frequency modulation is developed, so the developed electronic ballast operates in constant power, low crest factor. The developed CIC-CPPFC electronic ballast has features of low line input current harmonics, constant lamp power, low crest factor, continuous input current, low DC bus voltage stress, small circulating current and switching current stress over a wide range of line input voltage.
Analysis and Comparison of Space Vector Modulation Schemes for Three-Leg and Four-Leg Voltage Source Inverters
Prasad, V. Himamshu (Virginia Tech, 1997-05-15)
Several space vector modulation schemes have been analyzed for three-leg and four-leg voltage source inverters. The analysis is performed with respect to a) switching losses, b) total harmonic distortion, c) peak-to-peak ripple in the line current and d) the ease of digital implementation. The analysis is performed over the entire range of modulation index and for varying load power factors (leading and lagging) under both balanced and unbalanced load conditions. The analysis shows that the performance of four-leg inverters is similar to three-leg inverters for various space vector modulation schemes. The analysis also verifies the fact that a modulation scheme with good harmonic performance usually has high switching losses and vice-versa. The analysis is verified using simulation and experiments. A novel algorithm for the calculation of total harmonic distortion of PWM signals has been proposed.
Analysis and design of microprocessor-controlled peak-power-tracking system
Huynh, Phuong (Virginia Tech, 1992-05-14)
Analyses and designs of a peak-power tracking system using microprocessor control are performed. Large-signal stability of the system for various modes of operation is analyzed to predict system dynamics. The stability analysis is supported mainly by qualitative graphical representations of different component blocks of the system. Small-signal stability analysis around the equilibrium points is done to assure proper performance and operation of this particular peak-power tracking system. Specific design details and procedures are discussed, and predictions from the analyses are verified through hardware.
Analysis and design of multiple-output forward converter with weighted voltage control
Chen, Jing (Virginia Tech, 1994-02-09)
This work presents the modeling and analyses of multiple-output forward converters with weighted voltage control. Based upon the analyses, the systematic design methodologies and design tools are provided. A power stage de model including all the major parasitics, which are detrimental to the output voltages, is derived. A nonlinear programming based design tool is developed to search for the weighting factors. Five methods of stacking secondaries to improve cross-regulation are presented, and the improvement of cross-regulation is quantified. A small-signal model of the multiple-output converters with coupled output filter inductors and weighted voltage control is established. The small-signal characteristics are studied, and the model shows that the system behavior is very sensitive to the coupling coefficient, which has been reported, but never been quantified. The pole-zero interlaced condition is derived. A current-mode control small-signal model is also presented, which can predict all the observed phenomena of current-mode control. Compensator design is discussed for different types of power stage transfer functions for both voltage-mode and current-mode control.
Analysis and Evaluation of Soft-switching Inverter Techniques in Electric Vehicle Applications
Dong, Wei (Virginia Tech, 2003-04-22)
This dissertation presents the systematic analysis and the critical assessment of the AC side soft-switching inverters in electric vehicle (EV) applications. Although numerous soft-switching inverter techniques were claimed to improve the inverter performance, compared with the conventional hard-switching inverter, there is the lack of comprehensive investigations of analyzing and evaluating the performance of soft-switching inverters. Starting with an efficiency comparison of a variety of the soft-switching inverters using analytical calculation, the dissertation first reveals the effects of the auxiliary circuit's operation and control on the loss reduction. Three types of soft-switching inverters realizing the zero-voltage-transition (ZVT) or zero-current-transition (ZCT) operation are identified to achieve high efficiency operation. Then one hard-switching inverter and the chosen soft-switching inverters are designed and implemented with the 55 kW power rating for the small duty EV application. The experimental evaluations on the dynamometer provide the accurate description of the performance of the soft-switching inverters in terms of the loss reductions, the electromagnetic interference (EMI) noise, the total harmonic distortion (THD) and the control complexity. An analysis of the harmonic distortion caused by short pulses is presented and a space vector modulation scheme is proposed to alleviate the effect. To effectively analyze the soft-switching inverters' performance, a simulation based electrical modeling methodology is developed. Not only it extends the EMI noise analysis to the higher frequency region, but also predicts the stress and the switching losses accurately. Three major modeling tasks are accomplished. First, to address the issues of complicated existing scheme, a new parameter extraction scheme is proposed to establish the physics-based IGBT model. Second, the impedance based measurement method is developed to derive the internal parasitic parameters of the half-bridge modules. Third, the finite element analysis software is used to develop the model for the laminated bus bar including the coupling effects of different phases. Experimental results from the single-leg operation and the three-phase inverter operation verify the effectiveness of the presented systematic electrical modeling approach. With the analytical tools verified by the testing results, the performance analysis is further extended to different power ratings and different bus voltage designs.
Analysis of Direct-Soldered Power Module / Heat Sink Thermal Interface for Electric Vehicle Applications
Kim, Junhyung (Virginia Tech, 2001-04-27)
Reducing the thermal impedance between power module and heat sink is important for high-power density, low-cost inverter applications. Mounting a power module by directly soldering it onto a heat sink can significantly reduce the thermal impedance at the module / heat sink interface, as compared to the conventional method of bolting the two together with a thermal grease or some other interface materials in between. However, a soldered interface typically contains a large number of voids, which results in local hot spots. This thesis describes approaches taken to reduce voids in the solder layer through surface treatment, solder paste selection, and adjustment in solder-reflow conditions. A 15MHz scanning acoustic microscope (SAM), a non-destructive inspection tool, was used to determine the void content at the module / heat sink interface. The experimental results show that a significant reduction in thermal resistance can be achieved by reducing the void content at the soldered module / heat sink interface. Moreover, a comparison of the thermal resistances in cases using the worst soldering, which contains the largest voided area, ThermstrateTM and thermal grease are presented. Thermal performances of the modules are studied by simulation with Flotherm.
Analysis of Performance Characteristics of Electric Vehicle Traction Drive in Low Speed/Low Torque Range
Kouns, Heath (Virginia Tech, 2001-12-06)
In a world with a growing population there is a trend toward higher and higher energy usage. Because of the cost involved in producing extra energy, there is a need for more efficient usage of the energy that is already available. The issue of efficiency rings home especially clear with electric motors. Although induction motors are used in many different applications, the motors used in electric vehicles must be able to generate a large starting torque as well as operate over a wide speed range. This work analyzes the restrictions placed on the motor and inverter drive system. It also looks at the best method for controlling the drive in order to achieve the highest efficiency out of the drive. While other works have shown methods of achieve high efficiency out of the motor, it is the assertion of this work that the efficiency of the total drive is more important. It is to that end that this work analyzes the performance of an induction motor under low torque and speed where a traction drive utilizes the most energy.
Average current-mode control and charge control for PWM converters
Tang, Wei (Virginia Tech, 1994)
Two control schemes for PWM converters, average current-mode (ACM) control and charge control, are studied in this dissertation. The small-signal models are derived for continuous-conduction mode PWM converters employing these two controls. Sampled-data modeling is applied to the current loop modeling, and the obtained models are accurate up to half the switching frequency. The relationships between current loop instability and converter operating conditions for both controls are found for the first time. The derived models are verified by both time-domain simulations and experiments. The models can be used for both voltage loop and current loop analysis and designs. Comprehensive design guidelines for PWM converters with both controls are also provided. The small-signal characteristics of these two controls are compared with those of peak current-mode control. The applications of ACM control and charge control to power factor correction (PFC) circuits are studied. Charge control is applied to continuous-conduction mode flyback converter to achieve a single-stage PFC. The current loop instability in PFC circuit and its effect on the input EMI filter design are investigated. The trade-off between the current loop stability nlargin and line current distortion is also discussed.
Characterization of MnZn ferrite materials and finite element method for MnZn ferrite core loss calculations
Han, Ping (Virginia Tech, 1995-09-15)
This work presents the method of calculating the core loss in ferrite cores by using a linear and sinusoidal finite element solver based on the material property data (the complex permeability, the dielectric constant, and the AC conductivity) measured in the laboratory. Due to the lack of published material data and fundamental test procedures, this work also demonstrates the measurement techniques of material data which are necessary for the finite element analysis (FEA) of the ferrite core loss. First, a linear mathematical model of the ferrite core loss is formulated to characterize the hysteresis loss and the eddy current loss. The magnetic properties (the real and the imaginary components of the complex permeability) and the electric properties (the dielectric constant and the conductivity) are required. Second, the experimental procedures of those four properties are first presented. Toroids with 1.1 OD/ID ratios are selected as samples to obtain the magnetic properties. It is illustrated that the hysteresis loss should be measured at the frequency of interest, instead of DC, due to its frequency-dependence. The electric property data of ferrites are collected by using a disk sample which forms a capacitor. The conductivity tested is frequency-dependent due to the combination of the dielectric loss and the DC conduction loss. Finally, core loss simulations for the sample toroid, an EE core, and an RMIO core are performed and compared with the measurements. The flux and loss distributions are demonstrated in the last two cores. The hot spots are identified from the field plots.
Comparison of input current spectral components for flyback PWM and resonant converters
Kvalheim, Erik M. (Virginia Tech, 1991-01-29)
Analytical expressions describing the input current spectrum of the flyback Pulse-Width-Modulated, Zero-Current-Switched Quasi-Resonant-Converter, and Zero-Voltage-Switched Quasi-Resonant-Converter are derived in terms of normalized circuit parameters. These analytical results are tested against experimental results. The same numerical example is presented for these three converters in which the input current spectrum is computed for various line/load conditions and the results are mutually compared. Detailed experimental results are presented for the same three converters as well as for the flyback Zero-Voltage-Switched Multi-Resonant-Converter. The effects of any parasitic oscillations in the experimental circuit are also considered.
Control Strategies for High Power Four-Leg Voltage Source Inverters
Gannett, Robert Ashley (Virginia Tech, 2001-07-30)
In recent decades there has been a rapidly growing demand for high quality, uninterrupted power. In light of this fact, this study has addressed some of the causes of poor power quality and control strategies to ensure a high performance level in inverter-fed power systems. In particular, specific loading conditions present interesting challenges to inverter-fed, high power systems. No-load, unbalanced loading, and non-linear loading each have unique characteristics that negatively influence the performance of the Voltage Source Inverter (VSI). Ideal, infinitely stiff power systems are uninfluenced by loading conditions; however, realistic systems, with finite output impedances, encounter stability issues, unbalanced phase voltage, and harmonic distortion. Each of the loading conditions is presented in detail with a proposed control strategy in order to ensure superior inverter performance. Simulation results are presented for a 90 kVA, 400 Hz VSI under challenging loading conditions to demonstrate the merits of the proposed control strategies. Unloaded or lightly loaded conditions can cause instabilities in inverter-fed power systems, because of the lightly damped characteristic of the output filter. An inner current loop is demonstrated to damp the filter poles at light load and therefore enable an increase in the control bandwidth by an order of magnitude. Unbalanced loading causes unequal phase currents, and consequently negative sequence and zero sequence (in four-wire systems) distortion. A proposed control strategy based on synchronous and stationary frame controllers is shown to reduce the phase voltage unbalance from 4.2% to 0.23% for a 100%-100%-85% load imbalance over fundamental positive sequence control alone. Non-linear loads draw harmonic currents, and likewise cause harmonic distortion in power systems. A proposed harmonic control scheme is demonstrated to achieve near steady state errors for the low order harmonics due to non-linear loads. In particular, the THD is reduced from 22.3% to 5.2% for full three-phase diode rectifier loading, and from 11.3% to 1.5% for full balanced single-phase diode rectifier loading, over fundamental control alone.
Core loss characterization and design optimization of high-frequency power ferrite devices in power electronics applications
Gradzki, Pawel Miroslaw (Virginia Tech, 1992-03-30)
An impedance-based core loss measurement technique for power ferrites, the modeling and analysis of mechanisms of high-frequency losses, and design methodology for optimization for high-frequency magnetics are presented. The high-frequency losses of ferrite materials are characterized employing a large-signal impedance measurement technique. The impedance analyzer controlled through an IEEE-488 interface, measures the impedance of the inductor under test under large signal excitation via a power amplifier. The core loss is a form of a parallel resistance is derived from measured impedance characteristics. A wideband impedance probe, enables core loss characterization up to 100 MHz. A comprehensive analysis of all major loss mechanisms in ferrites is presented. A new form of residual losses due to a magnetoelectric effect is postulated to account for losses at high frequencies. Two models of losses in ferrites are proposed, one with emphasis on analysis of loss mechanisms, and the other with an emphasis on the design of high-frequency magnetic components. Both models include the important effect of static bias field, which is the case in many power electronics applications. Magnetic losses due to magnetostriction are measured. Dependence of magnetoelastic resonances on the magnetic bias. core material, core shape and size is studied. The influence of diffusion after-effect on core loss under time-varying bias field is investigated. Thermal stability of high-frequency magnetics is studied. A verification of one- and two- dimensional models of winding losses for solid and litz wire is performed. The optimum design method for high-frequency power transformers and inductors is proposed.
Design and Analysis of Piezoelectric Transformer Converters
Lin, Chih-yi (Virginia Tech, 1997-05-20)
Piezoelectric ceramics are characterized as smart materials and have been widely used in the area of actuators and sensors. The principle operation of a piezoelectric transformer (PT) is a combined function of actuators and sensors so that energy can be transformed from electrical form to electrical form via mechanical vibration. Since PTs behave as band-pass filters, it is particularly important to control their gains as transformers and to operate them efficiently as power-transferring components. In order to incorporate a PT into amplifier design and to match it to the linear or nonlinear loads, suitable electrical equivalent circuits are required for the frequency range of interest. The study of the accuracy of PT models is carried out and verified from several points of view, including input impedance, voltage gain, and efficiency. From the characteristics of the PTs, it follows that the efficiency of the PTs is a strong function of load and frequency. Because of the big intrinsic capacitors, adding inductive loads to the PTs is essential to obtain a satisfactory efficiency for the PTs and amplifiers. Power-flow method is studied and modified to obtain the maximum efficiency of the converter. The algorithm for designing a PT converter or inverter is to calculate the optimal load termination, YOPT, of the PT first so that the efficiency (power gain) of the PT is maximized. And then the efficiency of the dc/ac inverter is optimized according to the input impedance, ZIN, of the PT with an optimal load termination. Because the PTs are low-power devices, the general requirements for the applications of the PTs include low-power, low cost, and high efficiency. It is important to reduce the number of inductive components and switches in amplifier or dc/ac inverter designs for PT applications. High-voltage piezoelectric transformers have been adopted by power electronic engineers and researchers worldwide. A complete inverter with HVPT for CCFL or neon lamps was built, and the experimental results are presented. However, design issues such as packaging, thermal effects, amplifier circuits, control methods, and matching between amplifiers and loads need to be explored further.
Design of a Radial Mode Piezoelectric Transformer for a Charge Pump Electronic Ballast with High Power Factor and Zero Voltage Switching
Huang, Weixing (Virginia Tech, 2003-04-21)
In a conventional electronic ballast for a fluorescent lamp, inductor-capacitor-transformer tank circuit is used. A Piezoelectric Transformer (PT) can potentially be used to replace such a tank circuit to save space and cost. In the past, ballast design using a PT requires selecting a PT from available samples which are normally not matched to specific application and therefore resulting in poor performance. In this thesis, a design procedure was proposed for designing a PT tailored for a 120-V 32-W electronic ballast with high power factor, high efficiency and Zero-Voltage-Switching (ZVS) of the inverter transistors that drive the lamp. This involves selection of PT materials, determination of geometries and the number of physical layers of the PT. A radial mode piezoelectric transformer prototype based on this design process was fabricated by Face Electronics Inc. and was tested experimentally, the results showed that the ballast using this custom-made PT achieved high power factor, Zero-Voltage-Switching and a 83% overall efficiency.
The Design of an Asic Control Chip for a Forward Active Clamp Converter and the Investigation of Integratable Lateral Power Devices
Dong, Wei (Virginia Tech, 1997-10-01)
In Part I, the design of an ASIC control chip for a forward active clamp converter is presented. Integration of the control and drive circuit into one IC chip results in higher power density, higher reliability for the converter module. The designed ASIC control chip uses a 2.0 um N well Analog CMOS process, and is fabricated at MOSIS. The design procedures of the ASIC chip are explained, and experimental results are presented. Part II of the thesis focuses on the numerical investigation of several integratable lateral power devices. Lateral power devices are used in power IC designs because of their compatibility with analog & digital IC process. To obtain devices with high current density, large safe operating area, fast response and low cost is highly desirable for power ICs. In Part II of this thesis, several lateral power devices are discussed and simulated, including lateral IGBT, lateral MCT and double gate lateral MCTs. It is shown that lateral IGBT and lateral MCTs are good candidates for power IC applications.
Design of Radial Mode Piezoelectric Transformers for Lamp Ballast Applications
Baker, Eric Matthew (Virginia Tech, 2002-05-07)
In the past, radial-mode piezoelectric transformer (Transoner) design has been difficult due to the complex interaction between the physical and electrical circuit characteristics. Prior to a design procedure, experimental design by Face Electronics, LC led to a sample that could fit a ballast application enabling zero voltage switching (ZVS) for the semiconductors without the use of any external inductance. In the ballast circuit, the piezoelectric transformer is used to replace the conventional inductor-capacitor resonant tank saving valuable space and expense. With ballast in mind, a design process has been developed in this thesis to optimize radial mode transformers to fit specifically tailored applications. The graphical process described, allows the engineer to design in the capability of zero voltage switching for a half-bridge drive while simultaneously providing highly efficient performance. The problem of mounting a piezoelectric transformer to a circuit board has also been addressed in this thesis. A thermally conductive mounting technique has been developed which can enhance both the power capability and reliability of circuits utilizing these devices.
Developing Modeling and Simulation Methodology for Virtual Prototype Power Supply System
Li, Qiong (Virginia Tech, 1999-03-03)
This dissertation develops a modeling and simulation methodology for design, verification, and testing (DVT) power supply system using a virtual prototype. The virtual prototype is implemented before the hardware prototyping to detect most of the design errors and circuit deficiencies that occur in the later stage of a standard hardware design verification and testing procedure. The design iterations and product cost are reduced significantly by using this approach. The proposed modeling and simulation methodology consists of four major parts: system partitioning, multi-level modeling of device/function block, hierarchical test sequence, and multi-level simulation. By applying the proposed methodology, the designer can use the virtual prototype effectively by keeping a short simulation CPU time as well as catching most of the design problems. The proposed virtual prototype DVT procedure is demonstrated by simulating a 5 V power supply system with a main power supply, a bias power supply, and other protection, monitoring circuitry. The total CPU time is about 8 hours for 780 tests that include the basic function test, steady stage analysis, small-signal stability analysis, large-signal transient analysis, subsystem interaction test, and system interaction test. By comparing the simulation results with the measurements, it shows that the virtual prototype can represent the important behavior of the power supply system accurately. Since the proposed virtual prototype DVT procedure verifies the circuit design with different types of the tests over different line and load conditions, many circuit problems that are not obvious in the original circuit design can be detected by the simulation. The developed virtual prototype DVT procedure is not only capable of detecting most of the design errors, but also plays an important role in design modifications. This dissertation also demonstrates how to analyze the anomalies of the forward converter with active-clamp reset circuit extensively and facilitate the design and improve the circuit performances by utilizing the virtual prototype. With the help of the virtual prototype, it is the first time that the designer is able to analyze the dynamic behavior of the active-clamp forward converter during large-signal transient and optimize the design correspondingly.
Development of a low cost inverter controlled induction motor drive with emphasis on the effect of power factor correction
Diamantidis, Dimitrios (Virginia Tech, 1995-01-15)
In the fractional hp induction motor drive market, there is an absence of low-cost and compact designs. Moreover, given the massive production of appliances which require such drives, there is little need for high-performance microcontroller controlled drives, since the only adjustments to the drive are made at the factory. The developed drive achieves the low cost and compact aims by implementing with analog components the constant Volts per Hertz technique. This simple technique can be used regardless of whether the speed loop is open or closed. In addition, since there is a growing need for drawing sinusoidal currents from utilities both for an optimal utilization of the utility power plant capacity and to minimize the harmonics injected into it, the developed drive is preceded by a power factor correction circuit, and its effect on the drive’s performance is determined with measurements of the system efficiency and the input power factor. It is found that the decrease in the system efficiency with the PFC circuit is small, and takes place only for speeds lower than 0.72 p.u. for a fan load.

Browsing by Author "Chen, Dan Y."

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