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This paper deals with experimental and analytical investigations of the influence of thermomechanical processing conditions on the mechanical properties and electrical conductivity of PdNi5 alloy, in the form of wire Ø 0.15 mm, for making catalysts-catchers. Obtained results showed that mechanical properties and electrical conductivity depend on the applied regime of thermomechanical processing. Knowing the dependence of influence of parameters of thermomechanical processing regime on these properties enables the production of PdNi5 alloy with required characteristics for use in the process of catalytic oxidation of ammonia, that is solving problems of loss of platinum metals, especially platinum. The results of analytical investigations of influence of thermomechanical processing regime, by software package SPSS, on tensile strength, elongation and electrical conductivity of PdNi5 alloy in the form of wire Ø 0.15 mm showed that using a linear regression model the mutual influences of selected parameters of thermomechanical treatment on mechanical properties and electrical conductivity of PdNi5 alloy, can be adequately described and analyzed. The results showed that tensile strength and electrical conductivity were only slightly affected with a change of temperature and time of annealing while annealing time has significant influence on the elongation value. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR34029: Razvoj tehnologije proizvodnje Pd katalizatora-hvatača za smanjenje gubitaka platine u visokotemperaturnim procesima katalize]

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In three-phase applications, the six-switch boost power factor correction rectifier is themostwidely employed topology because of its good performance and cost effectiveness. A vast amount of literature that deals with this circuit is exclusively focused on various control schemes aimed at optimizing different aspects of its steady-state and/or transient performance. However, almost no literature is available on its startup procedure, which is an indispensable part of control design of any practical circuit. To fill this gap, in this paper, a detailed startup procedure is described. This three-step startup procedure ensures that the inrush currents stay below a specified level and that the output voltage increases monotonically to its reference value, i.e., it does not exhibit any overshoot. The proposed startup procedure is illustrated with MATLAB/Simulink simulation waveforms and also experimentally verified. [ABSTRACT FROM AUTHOR]

A new, three-phase, two-switch, power-factor-correction (PFC) rectifier that can achieve less than 5% input-current total harmonic distortion (THD) and features zero-voltage switching (ZVS) of all the switches over the entire input-voltage and load ranges is introduced. The proposed rectifier also offers automatic voltage balancing across the two output capacitors connected in series, which makes it possible to use downstream converters designed with lower voltage-rated component that offer better performance and are less expensive than their high-voltage-rated counterparts. In addition, the proposed rectifier also exhibits low common-mode EMI noise. The performance of the proposed rectifier was evaluated on a 2.8-kW prototype with a 780-V output that was designed to operate in 340–520-VL-L, RMS input-voltage range. [ABSTRACT FROM AUTHOR]

A bridgeless buck power factor correction rectifier that substantially improves efficiency at low line of the universal-line range is introduced. By eliminating input bridge diodes, the proposed rectifier's efficiency is further improved. Moreover, the rectifier doubles its output voltage, which extends useable energy of the bulk capacitor after a dropout of the line voltage. The operation and performance of the proposed circuit was verified on a 700-W, universal-line experimental prototype operating at 65 kHz. The measured efficiencies at 50% load from 115 and 230 V line are both close to 96.4%. The efficiency difference between low line and high line is less than 0.5% at full load. A second-stage half-bridge converter was also included to show that the combined power stages easily meet Climate Saver Computing Initiative Gold Standard. [ABSTRACT FROM PUBLISHER]

In universal-line ac/dc converters that require power factor correction (PFC), maintaining a high efficiency across the entire line and load ranges poses a major challenge. Typically, a boost PFC front end exhibits 1%-3% lower efficiency at 100-V line compared to that at 230-V line. It is shown in this paper that a buck PFC front end with an output voltage in the 80-V range can maintain a high efficiency across the entire line and load ranges. A thorough analysis of the buck PFC converter operation and performance along with design optimization guidelines are presented. Experimental results obtained on a 90-W notebook adapter are provided. A loss analysis based on SIMPLIS and PSPICE simulations is also included. Major factors that contribute to the improved efficiency of the buck PFC versus the boost PFC are briefly explained. [ABSTRACT FROM AUTHOR]

In this paper, a systematic review of phase-locked loop (PLL)-based closed-loop control methods for interleaved discontinuous conduction mode/continuous conduction mode (DCM/CCM) boundary boost power factor correction (PFC) converters is presented. A detailed analysis of the stability of the PLL with instant averaging filter is performed and verified by simulation. The stability of the PLL with instant averaging filter and with RC filter is compared by simulation. Based on the simulation results, it is concluded that the PLL-based closed-loop methods always provide stable operation, unlike the open-loop control methods, where the only method that results in stable operation is the slave synchronization to the turn-ON instant of the master with current-mode control. It is also shown that the dynamic response of the PLL-based closed-loop methods with master-slave approach and democratic approach is almost identical. Experimental results obtained on a 300-W, universal input, 400-V output, interleaved DCM/CCM boundary boost PFC prototype circuit with a dedicated controller IC utilizing a democratic, PLL-based closed-loop method are also provided. [ABSTRACT FROM AUTHOR]

In offline ac-dc and high-voltage dc-dc power supplies, galvanic isolation between the input and output is often implemented with optocoupler feedback. However, several disadvantages exist when implementing optocoupler feedback, such as a variable loop gain due to optocoupler tolerance and sensitivity to temperature, as well as a relatively high cost. An alternative to optocoupler feedback is to use magnetic feedback, which can be designed to have insensitivity to component tolerance, and good temperature stability. Although magnetic feedback has been in use for many years, a detailed analysis and clear design procedure has not been presented in the literature. This paper presents a thorough analysis of a magnetic-feedback implementation, and provides a comprehensive design procedure that is verified on a 7-V/15-W experimental prototype. [ABSTRACT FROM AUTHOR]

The implementation of a bridgeless power factor correction (PFC) boost rectiifier with low common-mode noise is presented in this paper. The proposed implementation employs a unique multiple-winding, multicore inductor to increase the utilization of the magnetic material. The operation and performance of the circuit were verified on a 750-W, universal-line experimental prototype operating at 110 kHz. [ABSTRACT FROM AUTHOR]

A systematic analysis of line-current distortions of the discontinuous-conduction-mode and the continuous-conduction-mode boundary boost power factor correction converter due to valley switching (VS) and switching-frequency limitation, where VS is either maintained or lost after the onset of switching-frequency limitation, is provided. Closed-form expressions for the line current are derived. It is shown that if the switching frequency is limited and VS is not maintained, the line current is more distorted with voltage-mode control than with current-mode control. The effects of line-current distortions are demonstrated with both simulation and experimental result. [ABSTRACT FROM AUTHOR]

In this paper, a systematic review of bridgeless power factor correction (PFC) boost rectifiers, also called dual boost PFC rectifiers, is presented. Performance comparison between the conventional PFC boost rectifier and a representative member of the bridgeless PFC boost rectifier family is performed. Loss analysis and experimental efficiency evaluation for both CCM and (DCM)/CCM boundary operations are provided. [ABSTRACT FROM AUTHOR]

Two implementations of the isolated boost converter that exhibit no parasitic voltage ringing across all semiconductor devices on the primary and secondary sides of the transformer are introduced. Ringing-free operation is achieved by clamping the voltages of the primary switches and rectifiers to the voltage of the primary-side energy-storage capacitor and clamping the voltage across the secondary-side rectifiers to the output filter capacitor. The performance of the proposed topology was verified on a dual ac-input, 900-W experimental prototype operating at 67 kHz. [ABSTRACT FROM AUTHOR]

A novel, two-inductor, interleaved power-factor-corrected (PFC) boost converter that exhibits voltage-doubler characteristic when it operates with a duty cycle greater than 0.5 is introduced. The voltage-doubler characteristic of the proposed converter makes it quite suitable for universal-line (90-264 VRMS) PFC applications. Because the proposed PFC boost rectifier operates as a voltage doubler at low line, its low-line range efficiency is greatly improved compared to that of its conventional counterpart. The performance of the proposed PFC rectifier was evaluated on an experimental 1.3-kW universal-line PFC prototype. [ABSTRACT FROM AUTHOR]

A soft-switched full-bridge (FB) converter that features zero-voltage-switching (ZVS) of the bridge switches over a wide output-load range is introduced. The proposed converter achieves ZVS with substantially reduced duty-cycle loss and circulating current. The control of the proposed converter can be implemented either with the phase-shift or pulsewidth modulated (PWM) technique. The performance of the proposed topology was verified on a 2-kW (48-V/40-A) experimental PWM FB converter prototype operating at 120 kHz from a 380-V dc input. [ABSTRACT FROM AUTHOR]

A circuit that substantially extends the hold-up time of ac-dc power supplies is introduced. By using integrated magnetics, the power density of this hold-up time extension circuit is maximized. The performance of the proposed approach was evaluated on a universal line range 1-kW power supply. [ABSTRACT FROM AUTHOR]

A novel implementation of the high-power-factor (HPF) boost converter with active snubber is described. The snubber circuit reduces the reverse-recovery-related losses of the rectifier and also provides zero-voltage switching for the boost switch and zero-current switching for the auxiliary switch. The performance of the proposed approach was evaluated on an 80-kHz, 1.5-kW, universal-line range, HPF boost converter. The proposed technique improves the efficiency by approximately 2% at full load and low line. [ABSTRACT FROM AUTHOR]

A detailed analysis of operation and a basic design procedure for a new high-frequency (HF) resonant-converter technology with phase-shifted regulation is presented. The new HF resonant technology has a good potential to be a cost-effective solution for the voltage regulation modules (VRMs) for the next generations of microprocessor systems. The new HF resonant technology is employed in the development of a 1.8-MHz, 48-V, 130-W (0.95-1.7 V, 100 A) VRM. Experimental results are provided. [ABSTRACT FROM AUTHOR]

This paper presents a magnetic integration approach that reduces the number of magnetic components in a power supply by integrating magnetic components in two conversion stages. Specifically, in the proposed approach, a single transformer is used to implement the continuous-conduction-mode boost power-factor-corrected (PFC) converter and the dc/dc flyback converter. The integrated boost and flyback converters offer soft switching of all semiconductor switches including a controlled di/dt turn-off rate of the boost rectifier. The performance of the proposed approach was evaluated on a 150-kHz, 450-W, universal-line range boost PFC converter with 12-V/2.2-A integrated stand-by flyback converter. [ABSTRACT FROM AUTHOR]

Optocouplers are widely used in isolated power supplies to transfer the feedback signal from the secondary to the primary side. In many power supplies, the feedback amplifier is supplied from the output voltage that creates additional feedback path which should be taken into account in the control design. The paper presents a detailed analysis and control design for each of the two possible feedback loops that can be identified. In addition, dynamic limitations of the TL431 shunt regulator and of the optocoupler are discussed. Practical guidelines for the error amplifier design and a design example are presented for both voltage-mode and current-mode controls. [ABSTRACT FROM AUTHOR]

A review of high-performance, state-of-the-art, active power-factor-correction (PFC) techniques for high-power, single-phase applications is presented. The merits and limitations of several PFC techniques that are used in today's network-server and telecom power supplies to maximize their conversion efficiencies are discussed. These techniques include various zero-voltage-switching and zero-current-switching, active-snubber approaches employed to reduce reverse-recovery-related switching losses, as well as techniques for the minimization of the conduction losses. Finally, the effect of recent advancements in semiconductor technology, primarily silicon-carbide technology, on the performance and design considerations of PFC converters is discussed. [ABSTRACT FROM AUTHOR]

A digital signal processor (DSP) implementation of digital control for constant-frequency, discontinuous-conduction-mode boost power-factor-correction converter for universal line- voltage (90.264 Vrms) applications is presented. A step-by-step design procedure based on digital redesign technique is also provided. The performance evaluation of the proposed DSP control is performed on a 400-W prototype. It was shown that the implemented DSP-based control can achieve a power factor higher than 0.99 in the entire line range. [ABSTRACT FROM AUTHOR]

A new, two-inductor, two-switch boost converter topology and its variations suitable for applications with a large difference between the input and output voltage are described. The output voltage regulation of the proposed converters is achieved in a wide load and input-voltage range with constant-frequency control by employing an auxiliary transformer that couples the current paths of the two boost inductors. [ABSTRACT FROM AUTHOR]

A high-performance contactless electrical energy transmission (CEET) technique which employs the inductive energy transmission principle is described. The proposed technique enables the implementation of high-efficiency high-power-density fully regulated CEET systems suitable for applications with a wide input and load range. A high efficiency of the system is achieved by recovering the energy stored in the leakage inductances of the transformer by incorporating them in the operation of the circuit, and by employing high-frequency-inverter and controlled-rectifier topologies that allow a controlled bidirectional power flow through the transformer. In addition, a feedforward variable-switching-frequency control of the inverter is used to maintain approximately constant power transfer through the transformer with the input voltage changes, whereas the output-side rectifier employs a local pulsewidth-modulation control to achieve a tight regulation of the output in the presence of load variations. Specifically, the described CEET system is suitable for use in universal-input battery chargers. [ABSTRACT FROM AUTHOR]

Compares the general properties of resonant, quasi-resonant, multi-resonant and pulse-width modulated soft-switching techniques. High-frequency power conversion techniques; Reduction of switching losses.

Angioleiomyoma represents a benign stromal tumor, which usually occurs in the subcutaneous tissue of the extremities, although its occurrence in the gastrointestinal tract is very rare. A case of rectal angioleiomyoma in a 40 year-old female patient is described here. Six months earlier, the patient suffered from periodical prolapse of an oval tumor from the anus, along with difficulties in bowel movement. A transanal extirpation of the tumor was performed. This is the first reported case in the English literature of a patient presenting with prolapsed angioleiomyoma of the rectum. During the immediate postoperative period, as well as 6 mo later, the patient had an unremarkable postoperative recovery.

Aim: To compare levels of combined exposure to white spirit, toluene, butyl acetate, ethyl acetate, and xylene in the manufacturing of paint, cartridge, drying, and top-coat sections of paint and lacquer industry, and peripheral nerve conduction parameters in the exposed workers., Methods: The exposed group comprised 120 workers while the control group included 110 workers who had never been exposed to the above listed organic solvents. Nerve conduction studies of the radial and tibial anterior nerve were performed in both groups., Results: Motor and sensitive conduction velocity, as well as terminal latency of the radial and tibial anterior nerve showed significant changes in exposed workers in comparison to those of the control group (p<0.001). These parameters were significantly changed in workers with long length exposure to the toxic agents. In early stages of exposure, neural conduction parameters of the radial nerve were the most sensitive parameters in detecting subclinical peripheral nerve changes (p<0.001). There was significant correlation between the nerve conduction changes and urinary levels of hippuric and methyl-hippuric acids (p<0.01)., Conclusion: The results of the study suggest neurotoxic effects of the mixture of white spirit, toluene, butyl acetate, ethyl acetate, and xylene detected in paint and lacquer industry. Standard measurement of the urinary levels of hippuric and methyl-hippuric acids could be a useful indicator of need for nerve conduction studies and the subclinical peripheral neuropathy screening in exposed workers.