Unfolded resonant converter with current doubler structure module for welding applications

A new multiphase resonant converter arrangement with series dual phase in the primary side and parallel dual current doubler in the secondary side, operating as a phase shift controlled current source is presented. Sharing the voltage and current stress among the active and passive components with a high DC input voltage and arc current motivates this structure, which also uses WBG devices to increase the efficiency at high switching frequency. The resulting module is intended to operate in continuous and pulsating mode and can be parallelized to extend the output arc current rate.This work was funded by the Spanish Ministry of Science and the EU through the project TEC2014-52316-R: ‘Estimation and Optimal Control for Energy Conversion with Digital Devices’ ECOTRENDD

Alternating current welding using four quadrant switches

Welding metals such as aluminum and magnesium requires AC current. This work proposes a novel control strategy for a high-frequency rectifier built with four quadrant switches (4QSW) to transform high frequency AC current (125 kHz) into the welding arc bipolar current, controlled in amplitude, frequency and even DC offset. The rectifier is connected to the output of a resonant inverter to achieve positive and negative polarity discharges both voltage and current by operating in two quadrants, i.e. positive and negative. As long as the input power to the converter is supplied by a current source, the typical dead-time set to avoid short circuit conditions jeopardize the safe operation of the switches. A field-programmable gate array (FPGA) is selected to implement the digital control due to its high resolution for the purpose to adapt the 4QSW's drive signals without dead-time in the most accurate manner.This work was supported by FEDER and the Spanish Ministry of Science through the project CICYT-FEDER TEC2011-23612: “Power conversion with new digital control techniques and soft-saturation magnetic cores

DC-DC Power Converter Design for Application in Welding Power Source for the Retail Market

The purpose of this study is to design and analyze a DC-DC power converter for application in a welding power source that is cost-competitive with the more traditional, lower-tech welding power source topologies. This thesis first presents a background study of recent design approaches to DC-DC power converters, as they relate to application in welding power converters. The background study also surveys recent design approaches to welding power source controls. Evaluation of available options in DC-DC converter topologies and switching schemes for application in a welding power source is presented. Design methodology of a low-cost DC-DC converter for application in a welding power source is explained in detail. The design criteria are presented, and systematically solved for using a combination of electrical theory and computer-based modeling. The power converter design is modeled and verified through simulation. An economic analysis of the design proves it to be economically feasible, but still not as inexpensive as traditional, lower-tech solutions currently in use in the arc welding retail market. The most expensive component of the design is the power switching components, which have the potential for further cost reduction, and is recommended as future wor

Induction motors versus permanent magnet actuators for aerospace applications

This paper introduces a comparative study on the design of aerospace actuators concerning Induction Motor (IM) and Permanent Magnet Motor (PMM) technologies. In the analysis undertaken, the two candidate configurations are evaluated in terms of both their electromagnetic and thermal behavior in a combined manner. On a first step, the basic dimensioning of the actuators and their fundamental operational characteristics are determined via a time-stepping Finite Element (FE) analysis. The consideration of the thermal robustness of the proposed motor configurations is integrated in the design procedure, through the appropriate handling of their respective constraints. As a result, all comparisons are carried out on a common thermal evacuation basis. On a second step, a single objective optimization procedure is employed, considering several performance and efficiency indexes using appropriate weights. Manufacturing and construction related costs for both investigated topologies are considered employing specific penalty functions. The impact of the utilized materials is also examined. The resultant motor designs have been validated through manufactured prototypes illustrating their suitability for aerospace actuatio

A series-parallel load-resonant converter for a controlled-current arc-welding power supply

A power supply incorporating a series-parallel load-resonant converter, capable of very efficient operation over a wide range of output power is presented. The series-parallel load-resonant converter is shown to have three pairs of resonant frequencies. Operation of the circuit at each of these resonant frequencies maintains zero current switching and high frequency operation. Design mathematics is developed which allow series-parallel load-resonant converters to be designed with specific resonant frequencies and circuit resistances. A new method of power control for series-parallel load-resonant converters is presented; the power delivered to the circuit and hence the load is shown to var substantially depending on which resonant frequency the circuit is excited at. Two series-parallel load-resonant converters are designed simulated, constructed and tested. There is good agreement between the simulation and experimental results. One of the circuits produces an output current of 200 A while the second demonstrates the new power control technique pulsing between 55 A and 145 A while running at frequencies of 63 kHz and 100 kHz. The new power supply is particularly suited to arc-welding. It contains an active rectifier and draws near unity power factor

Hardware Implementation and a New Adaptation in Winding Scheme of Standard Three Phase Induction Machine to Utilize for Multifunctional Operation: A New Multifunctional Induction Machine

publishedVersio

Index to 1983 NASA Tech Briefs, volume 8, numbers 1-4

Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1983 Tech Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

Thermal Robotic Arm Controlled Spraying via Robotic Arm and Vision System

The Tribology Surface Engineering industry is a worldwide multi billion euro industry with significant health and safety risks. The thermal spraying sector of this industry employs the technique of applying molten surface coating material to a substrate via a thermal spray process which is implemented either by manual spraying or pre-programmed robotic systems. The development of autonomous robotic systems for thermal spraying surface coating would significantly improve production and profitability over pre-programmed systems and improve health and safety over manual spraying. The aim of this research was to investigate and develop through software simulation, physical modelling and testing the development of robotic subsystems that are required to provide autonomous robotic control for the thermal spraying process. Computer based modelling programs were developed to investigate the control strategy identified for the thermal spaying process. The algorithms included fifth order polynomial trajectories and the complete dynamic model where gravitational, inertia, centrifugal and coriolis torques are considered. Tests provide detail of the load torques that must be driven by the robot electric actuator for various structural changes to the thermal spraying robot and for variations in trajectory boundary conditions during thermal spraying. The non-linear and coupled forward and inverse kinematic equations of a five axis articulated robot with continuous rotation joints were developed and tested via computer based modelling and miniature physical robot modelling. Both the computer based modelling and physical model confirmed the closed form kinematic solutions. A solution to running cables through the continuous rotation joints for power and data is present which uses polytetrafloraethylene (PTFE) electroless nickel. This material was identified during the literature review of surface coating materials. It has excellent wear, friction and conductivity properties. Physical tests on a slip ring and brushes test rig using electroless nickel are presented which confirm the viability of using PTFE electroless nickel as a slip ring. Measurement of the substrate during thermal spraying so as to autonomously control the thermal spaying robot is a significant challenge. This research presents solutions for the measurement of the substrate using a low cost camera system and lasers in a single wavelength environment. Tests were carried out which resulted in the removal of a butane flame obscuring a test piece requiring measurement from the camera image so that substrate measurements can be made using image processing and analysis techniques such as canny edge detection and centroid measurements. Test results for the low cost vision system provide depth measure errors of ±0.6 % and structural measurements such as area and perimeter in the range -5% to -7.5%. These results confirm the efficacy of this novel flame removal technique