Direct usage of photovoltaic solar panels to supply a freezer motor with variable DC input voltage

In this paper, a single-phase photovoltaic (PV) inverter fed by a boost converter to supply a freezer motor with variable DC input is investigated. The proposed circuit has two stages. Firstly, the DC output of the PV panel that varies between 150 and 300 V will be applied to the boost converter. The boost converter will boost the input voltage to a fixed 300 V DC. Next, this voltage is supplied to the single-phase full-bridge inverter to obtain 230 V AC. In the end, The output of the inverter will feed a freezer motor. The PV panels can be stand-alone or grid-connected. The grid-connected PV is divided into two categories, such as with a transformer and without a transformer, a transformer type has galvanic isolation resulting in increasing the security and also provides no further DC current toward the grid, but it is expensive, heavy and bulky. The transformerless type holds high efficiency and it is cheaper, but it suffers from leakage current between PV and the grid. This paper proposes a stand-alone direct use of PV to supply a freezer; therefore, no grid connection will result in no leakage current between the PV and Grid. The proposed circuit has some features such as no filtering circuit at the output of the inverter, no battery in the system, DC-link instead of AC link that reduces no-loads, having a higher efficiency, and holding enough energy in the DC-link capacitor to get the motor started. The circuit uses no transformers, thus, it is cheaper and has a smaller size. In addition, the system does not require a complex pulse width modulation (PWM) technique, because the motor can operate with a pulsed waveform. The control strategy uses the PWM signal with the desired timing. With this type of square wave, the harmonics (5th and 7th) of the voltage are reduced. The experimental and simulation results are presented to verify the feasibility of the proposed strategy

Arc behaviour and metal transfer of the VP-GMAW process

This project evaluated the metal transfer behaviour of the variable polarity (VP) GMAW process. Analysis was performed using high speed video that was synchronised with high speed data acquisition. Melting rate measurements were found to be very dependent on current waveform, polarity, and droplet size, and metal transfer if it occurred, for each waveform period. The transient conditions of current waveform and metal transfer produced rapid changes in arc behaviour which influenced the melting at the electrode tip and growing droplet. The concentrated melting theory was developed to explain the significant increase in electrode extension burnoff and droplet growth rate that occurred at short EN time as a function of current, and during EP peak pulse when the pre-pulse droplet volume was small. The highest electrode extension burnoff and droplet growth rate occurred when the arc was permitted to climb over the solid electrode tip producing rapid concentrated melting. Likewise, large molten droplets were found to promote a negative electrode extension burnoff and a decreased droplet growth rate. The arc rooted on large droplets providing additional heating but limited electrode melting. The droplet burnoff rate (DBR) method was developed and found to yield good experimental measurements for the arc and resistive heating coefficients used in a 2nd order melting rate equation developed for a complex waveform process, like VP-GMAW. For the EN period, the EN time affected the melting rate as a function of EN current. The greater melting rate that occurred at low EN time was measured by the changes in the resistive heating coefficient. Concentrated arc melting of the electrode extension at low EN time caused the slope of the burnoff diagram to increase, which represented the resistive heating coefficient. The melting rate of the EP pulse was related to the pre-pulse droplet volume. Large pre-pulse droplets decreased the arc heating coefficient, which could be negative, which meant the electrode extension was increasing and the arc length was decreasing in that waveform period. VP-GMAW power supplies offered stable operation for welding sheet structures on both carbon steel and stainless steel. Higher travel speeds were required as the %EN of the waveform increased to produce acceptable constant deposit area fusion. Welding speeds were up to 300% higher with VP-GMAW compared to the GMAW-P process when welding lap joints on 1.8 mm thick material with a 1.8 mm gap. VP-GMAW heat input was up to 47% less than GMAW-P for the same melting rate

SINGLE PHASE TO THREE PHASE CONVERTER FOR VARIABLE SPEED DRIVE APPLICATIONS

This final report is mainly to give an overview about the “Single phase to Three phase converter for variable speed drive applications” project and also the progress of the project. Due to unavailability and high cost installation of three phase power network, power inverter is very important to address this problem. Here comes the purpose of the project to develop electronic converters that applicable for three phase equipment that equipped with variable speed drive (VSD) applications to operate in single phase supply. This project proposed two converter topologies for circuit modelling and simulation. There are PRC and PWM method. The modeling for the project will be done using PSPICE software. The model will be simulating based on the load requirement which is 3-phase motor for the converter design. Based on the simulation analysis it has been proved that these two methods can be implemented in order to achieve the project’s objective which to produce 3 phase power from single phase supply with improved performance and better efficiency. For this given time frame the project only focus on the methodology on how to develop the converter using proposed method but without control strategy. Further improvement or works can be carried out to improve the design by implemented control strategy for the converter

Electrical bearing failures in electric vehicles

In modern electric equipment, especially electric vehicles, inverter control systems can lead to complex shaft voltages and bearing currents. Within an electric motor, many parts have electrical failure problems, and among which bearings are the most sensitive and vulnerable components. In recent years, electrical failures in bearing have been frequently reported in electric vehicles, and the electrical failure of bearings has become a key issue that restricts the lifetime of all-electric motor-based power systems in a broader sense. The purpose of this review is to provide a comprehensive overview of the bearing premature failure in the mechanical systems exposed in an electrical environment represented by electric vehicles. The electrical environments in which bearing works including the different components and the origins of the shaft voltages and bearing currents, as well as the typical modes of electrical bearing failure including various topographical damages and lubrication failures, have been discussed. The fundamental influence mechanisms of voltage/current on the friction/lubrication properties have been summarized and analyzed, and corresponding countermeasures have been proposed. Finally, a brief introduction to the key technical flaws in the current researches will be made and the future outlook of frontier directions will be discussed. Document type: Articl

Effect of interpass temperature on the structure and properties of multipass weldments in high performance nickel alloys

2011 Summer.Includes bibliographical references.Nickel alloys comprise an important group of engineering materials which are used primarily for their exceptional resistance to corrosion and their ability to maintain good mechanical strength over a wide temperature range, (both low and high) in demanding industrial applications. Welding is a primary fabrication process for these alloys. It has been a generally accepted practice to maintain a maximum interpass temperature of 200°F or lower when multipass welding many nickel alloys to prevent defects such as cracking or loss of corrosion resistance. This practice has been based on recommendations by many of the nickel alloy producers. A low maximum interpass temperature can increase the welding time which increases fabrication costs. According to the author's industry contacts and based upon the author's industrial experience as well as the author's examination of the literature, there has been little or no systematic research on the effect of interpass temperature for multipass welding of nickel alloys. In fact, the same is true for the establishment of the basic robotic welding parameters using the new generation of digital power supplies for these alloys. This dissertation presents research on the effect of interpass temperature on two nickel alloys; HASTELLOY® C-2000® and HASTELLOY® B-3®. Welding parameters were also developed for these alloys and also for HAYNES® 230® alloy using Gas Metal Arc Welding, GMAW, as a single process for both the root and fill weld passes. Weldments were made at 5 different interpass temperatures, 100°F - 500°F, in 100°F increments, for these alloys in thicknesses of 0.25 inch and 0.5 inch. Transverse weld specimens were then tested according to AWS B4.0:2007 using tensile, bend, and hardness tests. Transverse weld specimens were corrosion tested according to ASTM G28A for the HASTELLOY C-2000 alloy and the HASTELLOY B-3 alloy was subjected to 20% HCl at 149°C for 96 hours in an autoclave. The specimens were also examined using optical light microscopy for intergranular corrosion attack, weld fusion, cracking, and heat affected zone (HAZ) microstructure effects. (HASTELLOY, HAYNES, C-2000, B-3, and 230 are registered trademarks of Haynes International, Inc.) No significant loss of tensile strength was found at any of the higher interpass temperatures. All ultimate tensile strengths for both alloys were above the ASME Boiler and Pressure Vessel Code Section IX minimum. All samples passed 2T transverse face bend tests. Some lack of fusion was observed at the root of some samples at random interpass temperatures. No noticeable change in the HAZ microstructure or cracking was observed at the highest interpass temperature for both the HASTELLOY C-2000 and the HASTELLOY B-3 alloys. No significant corrosion attack was found along the weld, face or root sides, for both alloys at the higher interpass temperature of 500°F. It was concluded that a higher interpass temperature could be specified for these alloys without any appreciable loss of strength, weld soundness, loss of corrosion resistance, or detrimental effect to microstructure. It was also shown that the GMAW process could be used as a sole welding process but more development is needed to decrease process variability in the root pass and to develop a complete welding procedure specification

Power Semiconductors for An Energy-Wise Society

This IEC White Paper establishes the critical role that power semiconductors play in transitioning to an energy wise society. It takes an in-depth look at expected trends and opportunities, as well as the challenges surrounding the power semiconductors industry. Among the significant challenges mentioned is the need for change in industry practices when transitioning from linear to circular economies and the shortage of skilled personnel required for power semiconductor development. The white paper also stresses the need for strategic actions at the policy-making level to address these concerns and calls for stronger government commitment, policies and funding to advance power semiconductor technologies and integration. It further highlights the pivotal role of standards in removing technical risks, increasing product quality and enabling faster market acceptance. Besides noting benefits of existing standards in accelerating market growth, the paper also identifies the current standardization gaps. The white paper emphasizes the importance of ensuring a robust supply chain for power semiconductors to prevent supply-chain disruptions like those seen during the COVID-19 pandemic, which can have widespread economic impacts.The white paper highlights the importance of inspiring young professionals to take an interest in power semiconductors and power electronics, highlighting the potential to make a positive impact on the world through these technologies.The white paper concludes with recommendations for policymakers, regulators, industry and other IEC stakeholders for collaborative structures and accelerating the development and adoption of standards

Optimisation of autoselective plasma regeneration of wall-flow diesel particulate filters

The increase in number of diesel powered vehicles has led to greater concern for the effects of their exhaust emissions. Engine manufacturers must now consider using diesel particulate filters to make their engines meet the legislated limits. Diesel particulate filters can remove more than 95% of the particulates from the exhaust flow but require cleaning, known as regeneration. This thesis describes the research and optimisation of the Autoselective regeneration system for cordierite wall flow diesel particulate filters. The novel Autoselective technology uses an atmospheric pressure glow discharge plasma to selectively oxidise particulate matter (soot) trapped within the filter. The aim of this research was to produce a regeneration system that can operate under all exhaust conditions with a low energy demand and no precious metal dependence to compete with the numerous pre-existing technologies. The effect of discharge electrode type and position on regeneration performance has been investigated in terms of regeneration uniformity, power requirement and regeneration rate. The results showed that the electrode orientation had a large effect on regeneration distribution and energy demand. The electrode capacitance and breakdown voltage was shown to affect the choice of power supply circuit because not all power supply topologies were suitable for powering electrodes with >100 pF capacitance. A number of power supplies were designed and tested, a voltage driven resonant transformer type supply was shown to be optimal when used in conjunction with a swept frequency. The current and frequency ranges of electrical discharges were continuously variable, and their effect on discharge regeneration performance was studied. The results showed that the discharge frequency had no effect on the regeneration process but did affect spatial distribution. An optimised resonant transformer power supply was designed that was ideally suited for the electrodes used. A novel power modulation strategy, which used a switching frequency phase locked to the ~ iii ~ modulating frequency, was employed which extended the operating range of the discharge to below 10 mA for electrode separations > 7.5 mm. The heat flows within the filter and discharge during regeneration were analysed and the filter damage process was linked to the heat released by the discharge inside the filter wall. Other filter materials were compared based on the findings and Mullite ceramic was identified as a potentially better filter material for Autoselective regeneration. The filtration efficiency is important and was observed to be affected by the Autoselective process. The effect of the discharge on filtration efficiency was studied and the mechanism of particulate re-entrainment was identified as a combination of electrostatic and electro-acoustic forces. The Autoselective technology was successfully implemented in both flow-rig and on-engine tests. Results showed significant reduction in back-pressure for power inputs of ~ 500 W. The understanding of the Autoselective regeneration system has been improved and the research resulted in a novel method of filter regeneration

Welding of X100 linepipe

The benefits of high strength steels in terms of reduced material volume due to enhanced mechanical performance have been known for some time. Large diameter transmission linepipe steels of minimum 690MPa ('XIOO') yield strength have been developed throughout the previous decade, and have recently become commercially available. Before these steels are used in linepipe construction projects, fimdamental work regarding their ability to be field welded required undertaking. This thesis presents data arising from girth welding experiments involving a variety of X 100 linepipe steels, welding consurnables and welding processes. Target girth weld mechanical properties thought suitable for a strain-based MOO pipeline design were proposed at the outset of the research. Optimisation of pulsed gas metal arc welding waveforms for the single and tandem wire processes, alongside the establishment of the base material properties formed an early part of the research. An extensive programme of solid wire welding consumable evaluation was then undertaken for single, tandem and dual torch narrow gap welding processes. The majority of equipment and procedures used throughout the work were as close to current field practice as possible, to minimise the time required to transfer the technology to the field situation. Work then focussed on the optimised alloy levels and welding procedure requirements for the production of full girth welds, using a variety of industry pipeline welding standards and supplemental techniques to assess the joint integrity. It has been demonstrated that, subject to careful selection of welding consumable and fairly precise control of welding process variables and parameters, there are no major problems in obtaining weld metal strength levels of at least 120 MPa above the 690 MPa specified minimum yield strength (SMYS) of the parent pipe. This objective has been achieved in welds made usirig all three mechanised process variants examined. The desired target properties of strength and toughness were achieved with a variety of consumables and pipe materials of different composition. Tie-in and repair procedures were also developed during the course of the research, with particular attention focussed on the application of high strength rutile flux cored ýVires. These wires attained strength levels overmatching the pipe specified minimum yield strength (690MPa), but would not reach the guaranteed overmatch level of 81 OMPa. An examination of the thermocycles associated with four mechanised narrow gap welding techniques (single, tandem, dual and dual tandem) was undertaken. The experimental technique developed allowed the solidifying weld bead to be monitored, as well as the cumulative temperature cycles experienced by the underlying layers. Succesful determination of the cooling rates, times and transformation temperatures allowed a comparative evaluation of the four processes, using an optimum weld metal composition suitable for single wire welding of X100. This led to an understanding of the metallurgical history, and its consequent effect on the associated mechanical and microstructural properties. A similar series of experiments was undertaken to examine these effects using variations in preheat with a single wire process. In most cases considerable property variations were attained for'the same weld metal chemistry, joint geometry and arc energy, highlighting the sensitivity of the process and procedure in achieving the required properties. The high cooling rates determined from the thermocycle experiments explained the microstructural and mechanical properties attainable from lean alloying levels. A series of metal cored wires, based around the same alloy as for the thermocycle experiments, was consequently manufactured to examine small changes in weld metal chemistry. The individual wires involved changes in carbon, nickel, molybdenum and chromium to examine potential property variations arising from a highly controlled narrow gap welding procedure. The results again highlighted the sensitivity of the narrow gap welding technique in generating considerable property variation within the weld metal. Tolerance ranges for specific alloying additions to attain the proposed strength levels with a single and tandem wire process were derived from the data