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Electric Power Applications, IEE Proceedings -

Issue 3 • Date May 2003

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Displaying Results 1 - 16 of 16
  • Rotor topologies for a switched-reluctance machine for the 'more-electric' aircraft engine

    Publication Year: 2003 , Page(s): 311 - 318
    Cited by:  Papers (9)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (903 KB)  

    The merits of alternative rotor topologies for a switched reluctance machine that is to be embedded within the high-pressure region of a civil aircraft engine are discussed. The constraints imposed by conventional rotor designs due to the limited mechanical strength of the laminations are highlighted by finite element analysis of the stress distribution. A modular rotor structure is proposed which facilitates a significant reduction in the mechanical stress in rotor laminations, and thereby an increase in the diameters. Both two- and three-dimensional finite element analyses are employed to compare the electromagnetic performance of a switched reluctance machine with a modular rotor against two machines having conventional rotors. View full abstract»

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  • FPGA-based ASIC design of the three-phase synchronous PWM flyback converter

    Publication Year: 2003 , Page(s): 263 - 268
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (611 KB)  

    The design and development of a synchronous pulse-width modulation (PWM) generator suitable for the three-phase flyback converter is presented. The design is based on the Xilinx chip XC4005E field programmable gate array (FPGA). Two 30° of sine waveforms with two different carrier waveforms are used to generate the PWM. The PWM pattern proposed occupies less FPGA block cell, hence more space can be used for other control circuitry. The proposed technique enables the modulation index and the displacement factor to be changed externally. Results are provided to demonstrate the effectiveness of the design. View full abstract»

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  • Simple method for speed and rotor resistance estimation of induction machines

    Publication Year: 2003 , Page(s): 289 - 294
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (633 KB)  

    An approach to estimate the speed and rotor resistance of an induction machine from measured terminal voltages and currents is described. In this approach, the speed and rotor resistance are considered to be unknown constants, because the speed and rotor resistance change slowly compared to the electrical variables such as currents and fluxes. Based on this assumption, a new speed and rotor resistance estimator is defined and its performance is analysed and verified experimentally. View full abstract»

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  • Three-level inverter configuration cascading two two-level inverters

    Publication Year: 2003 , Page(s): 245 - 254
    Cited by:  Papers (24)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (917 KB)  

    A power circuit configuration to realise three-level inversion is proposed. Three-level inversion is realised by connecting two two-level inverters in cascade, in the proposed configuration. An isolated DC power supply is used to supply each inverter in this power circuit. Each DC-link voltage is equal to half of the DC-link voltage in a conventional NPC (neutral point clamped) three-level inverter topology. Neutral point fluctuations are absent, and fast recovery neutral clamping diodes are not needed. The proposed inverter scheme produces 64 space-vector combinations distributed over 19 space-vector locations as compared to 27 combinations in a conventional three-level topology. The present power circuit can be operated as a two-level inverter in the range of lower modulation, by clamping one inverter to a zero state and by switching the other inverter. When compared to the H-bridge topology, this circuit needs one power supply less. A space vector based PWM scheme is used for the experimental verification of the proposed topology. View full abstract»

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  • Three-phase harmonic load flow in frequency and time domains

    Publication Year: 2003 , Page(s): 295 - 300
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (647 KB)  

    A hybrid method in the time and frequency domains has been developed for the analysis of the harmonic distortion in power systems. This method is more complete than others reported in the literature and it allows both balanced and unbalanced systems to be considered. The linear elements of a network are modelled in the frequency domain while the nonlinear elements are modelled in the time domain, which permits consideration of all topologies and configurations. Acceleration techniques are used for finding the steady state in time-domain methods. Linear and nonlinear loads can be specified in terms of power by integrating a three-phase load-flow algorithm for the fundamental frequency with a hybrid algorithm for the harmonic interaction analysis. The proposed method tries to solve the present problems to study harmonic-distortion propagation in a power system. The integration of two complex and different algorithms is done here for the first time and offers great possibilities for power-systems analysis. View full abstract»

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  • Closed-form oriented loop compensator design for peak current-mode controlled DC/DC regulators

    Publication Year: 2003 , Page(s): 351 - 356
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (562 KB)  

    A formulated stepwise closed-form loop compensator design procedure for peak current-mode control DC/DC regulators is presented. As a result, a conventional computer software program such as Excel 5.0 can be used to systemise and to increase the efficiency of the design process. A prototype hardware circuit is constructed and some simulation and experimental results are presented. View full abstract»

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  • Analytical investigation of an induction motor drive under inverter fault mode operations

    Publication Year: 2003 , Page(s): 255 - 262
    Cited by:  Papers (14)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (730 KB)  

    Improved reliability and fault tolerant operations of converter systems are extremely important for industrial AC drives. An induction motor drive with fault tolerance capability is investigated though an analytical model. After the faulted leg in the six-step voltage source inverter operation has been detected, the motor is driven by the converter reconfiguration known as the four-switch inverter, but with reduced performances. Two possible modes of operation, utilising only four possible voltage vectors, in different ways can be used. For both modes of operation an analytical closed-form solution of the motor currents is derived. Theoretical waveforms are verified by experiments. Experimental results are in good agreement with the theoretical predictions. View full abstract»

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  • Linear analysis of two-, three- and four-phase switched reluctance machines with variable pitched winding configurations

    Publication Year: 2003 , Page(s): 319 - 343
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2201 KB)  

    The results from a generalised linear analysis of switched reluctance machines with various winding and phase configurations are presented. The generalised analysis is used to analyse ten 4/2, 6/4, and 8/6 pole machines with various stator coil pitches and excitation patterns. Twenty-six combinations are analysed with a fixed frame size. The optimum stator and rotor pole arc combinations for maximum torque per unit current production are determined. An iterative procedure is then used to determine the optimum rotor diameter, given the frame size, permissible total copper loss and flux density. The restrictions on copper loss and flux density provide a reasonable comparison between the average torque developed by each machine. The technique is linear, therefore it does not incorporate saturation and pole flux fringing effects. The analysis highlights that the optimised machine geometry is a function of the current excitation pattern and coil pitch employed. View full abstract»

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  • ZCS-ZVS bi-directional phase-shifted DC-DC converter with extended load range

    Publication Year: 2003 , Page(s): 269 - 277
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (921 KB)  

    The work described is based on a bidirectional phase-shifted DC-DC converter that conventionally suffers from the restricted load range and nonlinear control of the output voltage. The concepts developed are used to extend the load range of the converter by applying both zero current switching (ZCS) and zero voltage switching (ZVS). In addition, the control to output voltage characteristics of the converter is improved to be more linear over the large load range. View full abstract»

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  • Design and performance comparison of a stationary frame digital current control for a PM synchronous motor

    Publication Year: 2003 , Page(s): 357 - 364
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (794 KB)  

    An improved stationary frame-based digital current control technique for a permanent magnet (PM) synchronous motor is considered. The stationary frame current controller is known to have the advantage of simple implementation. However, there are some unavoidable limitations such as a steady-state error and a phase delay in the steady-state when using the proportional-integral (PI) controller. This control performance can be greatly improved by employing the exact decoupling control inputs for the back EMF, resulting in an ideal steady-state control characteristic irrespective of the operating condition, as in the synchronous PI decoupling controller. However, its steady-state response may be degraded by the inexact cancellation inputs due to the variation in the parameter. To improve the control performance in the stationary reference frame, the disturbance is estimated using a modified time-delay control. The proposed control scheme is implemented on a PM synchronous motor using DSP TMS320C31. The simulations and experiments verify that an improved control performance can be obtained in the stationary reference frame. View full abstract»

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  • Two-phase supply of three-phase transformers. I. Stacked core type transformers

    Publication Year: 2003 , Page(s): 283 - 288
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (491 KB)  

    The three-phase supply of distribution transformers sometimes changes unexpectedly to two-phase supply, due to external reasons, e.g. a burned fuse or interruption of one of the phases. In this case, secondary voltages result, which are no longer equal to the nominal phase voltage in all phases, i.e. one voltage is still equal to the nominal voltage, while the other two are not, but their vector sum is also equal to the nominal voltage, since it is obtained from the same primary polar voltage. This occurs for all connections except the star-to-star connection, for which none of the secondary voltages is equal to the nominal phase voltage. The magnitude of each voltage depends on the ampere-turns, the core dimensions and the magnetic permeability that appears in each core branch (limb). These voltages are calculated from the equivalent magnetic circuit and the magnetising curve of the core material. View full abstract»

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  • Enhancement and laboratory implementation of neural network detection of short circuit faults in DC transit system

    Publication Year: 2003 , Page(s): 344 - 350
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (642 KB)  

    The continuing development of neural networks for real-time detection of DC short circuit faults in DC transit systems is described. The discrete wavelet transform has been previously applied to detect any surges in DC third rail current waveform. In the event of a surge, the wavelet transform extracts a feature vector from the current waveform and feeds it to a self-organising neural network. The neural network then determines whether the feature vector belongs to a fault current surge due to short circuit occurring across the DC-link capacitor within a chopper train, or to a normal surge due to the starting of the chopper train. Perfect classification has been achieved between different cases of train starting and short circuits. The robustness of the neural network is further proven using extended data sets for training and testing and laboratory implementation. A new simulation model for the inverter trains is developed. A new type of short circuit fault occurring between third rail and track is modelled. For testing the fault detection scheme within the laboratory environment, a hardware model of the DC transit system is carefully built using an induction motor, laboratory power supplies and electronic models of railway components. Two neural networks are trained using the simulation data, and tested using the simulation and laboratory-measured data. Perfect classification is again achieved from both neural networks. The laboratory environment provides a valuable platform for fine-tuning the neural networks and for in-depth studies into the effects of practical constraints such as measurement noises and nonlinearities of the hardware models. View full abstract»

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  • Erratum

    Publication Year: 2003 , Page(s): 372
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    First Page of the Article
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  • Electronic ballast with piezoelectric transformer for cold cathode fluorescent lamps

    Publication Year: 2003 , Page(s): 278 - 282
    Cited by:  Papers (14)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (433 KB)  

    To miniaturise the ballast circuit, a half-bridge series-resonant inverter with a cascading Rosen-type piezoelectric transformer (PT) is designed for cold cathode fluorescent lamps (CCFLs). The PT is interposed between the resonant circuit and the lamp as a stage of the voltage amplifier to increase the lamp voltage and hence to reduce the sizes of the reactive components. The circuit parameters are designed to operate the inverter at a switching frequency that will have the highest boost ratio of PT, and with zero voltage switching (ZVS) for the active power switches to achieve high circuit efficiency. The lamp power is regulated by duty-ratio control with asymmetrical pulsewidth modulation (APWM). An electronic ballast designed for a 2.2 W CCFL is built and tested to verify the; simulated results. View full abstract»

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  • DSP-based PLL-controlled 50-100 kHz 20 kW high-frequency induction heating system for surface hardening and welding applications

    Publication Year: 2003 , Page(s): 365 - 371
    Cited by:  Papers (14)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (634 KB)  

    A digital signal processor (DSP)-based phaselocked loop (PLL)-controlled high-frequency induction heating system is described. The rectifier and insulated gate bipolar transistor (IGBT) inverter are controlled by a TMS320F240 DSP system, which has the hardware feature of providing a dead-band delay independent of the frequency of operation. This feature, together with the high speed of the DSP, allows the use of zero current resonant switching at a high power factor for frequencies up to 100 kHz. Resonant operation of the inverter is maintained by a simple digital PLL scheme implemented on the DSP. The frequency converter enables safe operation at all load conditions with digital overcurrent, overvoltage and overtemperature protection features. The cost-effective system described is operated successfully at outputs up to 19.8 kW at 72 kHz and 500 V. View full abstract»

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  • Reduction in conducted EMI noises of a switching power supply after thermal management design

    Publication Year: 2003 , Page(s): 301 - 310
    Cited by:  Papers (6)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1294 KB)  

    Owing to the increasing power density of a switching power supply (SPS), the placement of the components for thermal management and electromagnetic interference (EMI) characteristics is more difficult to design at a given form factor. When thermal management is a critical issue for the SPS, then methods for improving EMI noises seem not to be simultaneously successful at this design stage. As a result, the conducted EMI noises will deteriorate due to the placement of components for thermal management. Furthermore, the performance of the designed EMI filter will deteriorate due to severe internal electromagnetic interference, and thus lead to failure in the EMI conducted measurement. To improve this condition, the locations of EMI noise sources, modes of conducted EMI noise, their coupling paths and the characteristics of the electromagnetic field are investigated in detail. Various shielding schemes are proposed to reduce the EMI inside the SPS. Through this, the interference between the EMI sources, coupling paths and receivers can be significantly reduced so that the conducted EMI measurement of the SPS can meet the requirements. Finally, the effectiveness of the shielding schemes is demonstrated by some experimental results and some EMI reduction methods are suggested. View full abstract»

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