Copper Busbar Research Articles

An analytical algorithm to determine allowable ampacities of horizontally installed rectangular bus bars

The main objective of this paper is to propose an algorithm for the determination of the allowable ampacities of single rectangular-section bus bars without the occurrence of correction factors. Without correction factors, the ampacity computation of the copper and aluminium bus bars is fully automatized. The analytical algorithm has been implemented in a computer program code that along with the allowable ampacity can compute the bus bar temperature and the individual heat transfer coefficient for each side of the bus bar, as well as their corresponding power losses. Natural and forced convection correlations for rectangular bus bars are applied. Effects of the solar radiation and radiation heat losses from the bus bar surface are taken into consideration as well. The finite element method (FEM) has been used for the linear/non-linear steady-state thermal analysis, i.e. for validation of the analytical algorithm. All FEM-based numerical computations were carried out using the COMSOL Heat Transfer Module.

Non-contacting Busbars for Advanced Cell Structures Using Low Temperature Copper Paste

Abstract We report the use of a screen-printable copper paste to form the front busbars on high efficiency photovoltaic cell structures in combination with copper fingers formed by light induced plating. Such a process route offers economic benefits relative to the fully plated front metallization due to the reduced requirement for laser ablation and increased cell performance. We demonstrate improved open circuit voltage and fill factor compared to cells that used plating for both the fingers and the busbars. These result from reduced contact between the semiconductor and the metal and from reduced shunting compared to the laser ablated and plated electrodes. p-type ‘PERC’ cells have been fabricated with copper plated fingers and screen-printed copper busbars with a median cell efficiency of 20.4%, compared to 20.3% for those with fully plated busbars. n-type ‘PERT’ cells reached a cell efficiency of 20.9% for both front metallization schemes. The screen-printed busbars gave a ∼5 mV advantage over the plated busbars in both cases.

제련설비용 대전류 동 Bus Bar의 온도해석

제련설비용 대전류 동 Bus Bar의 온도해석

Dynamic Stress Analysis of Battery Tabs Under Ultrasonic Welding

Ultrasonic metal welding is widely used for joining multiple layers of dissimilar metals, such as aluminum/copper battery tabs welding onto copper busbars. It is therefore important to have a robust product/process design using ultrasonic metal welding that ensures consistent welds with desired quality. In this work, the effects of longitudinal and flexural vibrations of the battery tab during ultrasonic welding on the development of axial normal stresses that occasionally cause cracks near the weld area are studied by applying a one-dimensional continuous vibration model for the battery tab. Analysis results indicate that fracture could occur near the weld area, due to low cycle fatigue as a result of large dynamic stresses induced by resonant flexural vibration of the battery tab during welding. This study provides a fundamental understanding of battery tab dynamics during ultrasonic welding and its effects on weld quality, and can be used to develop guidelines for product/process design of ultrasonically welded battery tabs.

Passivated Busbars from Screen-printed Low-temperature Copper Paste

A screen-printable copper paste has been developed by Dow Corning to replace the standard screen-printable silver paste for use in front busbars for solar cells. Solar cells produced with these ‘passivated copper busbars’ have shown increased conversion efficiency due to an improved device operating voltage and current while maintaining a similar fill factor when compared to cells with standard ‘fired-through’ silver busbars. In addition to the improved cell efficiency, the use of copper paste may provide major cost savings compared to the use of silver, potentially giving a very significant reduction in cost per Watt. 60-cell modules have been produced at Trina Solar with passivated copper busbars, showing similar performance to the reference modules with silver busbars. Module reliability has been shown to be well in excess of the IEC 61215 standard requirements.

Preparation of Copper Electrical Engineering Alloy Strip with High Service Properties

Output is organized for industrial batches of electrical engineering strip with improved service properties, i.e., copper bus bars of rectangular section (σ u determination is simplified and surface quality evaluation after bend testing is improved), commutator copper-cadmium strip of trapezoidal section (hardness increased, strip camber reduced, bulges and scratches absent from basic profile), and commutator coppersilver strip (electrical conductivity increased and stable mechanical properties achieved).

Rapid Sintering Nanosilver Joint by Pulse Current for Power Electronics Packaging

Sintering of nanosilver paste has been extensively studied as a lead-free die-attach solution for bonding semiconductor chips. The bonding process typically consists of a low-temperature drying step to remove organic solvents in the paste followed by sintering at around 250°C . Normally, a soak time of several minutes at the sintering temperature is necessary to establish strong bond strength by the conventional heating method. In this paper, we tested the feasibility of applying pulses of alternating electrical current through the nanosilver bonding layer to achieve strong joints in less than a second, not minutes. Experiments were carried out by joining rectangular copper blocks that were either coated with a layer of electroplated silver or without. A layer of nanosilver paste was stencil printed on one block, dried at temperature below 100°C, before the other copper block was placed on. The bonding members were then inserted under an alternating-current spot-welding machine for rapid joining with current pulses. Die-shear test was used to quantify the joint strength. Investigated processing variables on the joint strength were current level, current-on time, nanosilver bondline thickness, predrying temperature and time, and copper surface finish. Scanning electron microscopy was used to characterize the joint microstructure. It is suggestive that the current sintering of nanosilver paste could be used for rapid joining of metal-to-metal connection, such as bonding copper bus bars onto power electronics modules.

Effect of Contact Pressure on the Resistance Contact Value and Temperature Changes in Copper Busbar Connection

This paper discussed the influence of tightness or contacts pressure on copper busbar joints to determine changes in the value of the initial contact resistance and the maximum temperature at the joint due to high current load. The test sample was copper busbar 3 x 30 mm with configuration of bolted overlapping joint. Increasing contact pressure at the joint was measured to find out its effect on the value of contact resistance. The applied pressure was 6 to 36 MPa. Procedure of contact resistance measurement refer to the ASTM B539 standard using four-wire method. The sample subsequently loaded with the current of 350 A for 60 minutes and the maximum temperature at the joint was measured. The result showed that increasing contact pressure at the busbar joint will reduce the contact resistance and maximum temperature. The increase of contact pressure from 6 to 30 MPa causes decreasing contact resistance from 16 μΩ to 11 μΩ. Further increasing of contact pressure more than 30 MPa did not affect the contact resistance significantly. The lowest temperatur of busbar joint of 54°C was reached at a contact pressure of 36 Mpa.

The Partial Discharge Characteristics Study of the Insulated Copper Busbar Joint Metal Metal Protrusion Defect

Insulated copper busbar is widely used as a new type of electrical equipment in recent years. The joint of the busbar is linked with soft connection copper belt in the field. So, it is very easily lead to the metal protrusion defect at the joint. The metal protrusion detect at joint with entity insulated copper busbar is builded in lab. The partial discharge characteristics of this defect is studied under different applied voltage and the results show that such defect has apparent polarity effect, the discharge always appears in the negative half cycle. The discharge amplitude will not be increased very much with increasing of applied voltage but the discharge frequency will be increased significantly. The results provide the basis of laboratory studies for the field testing of insulated copper busbar.

Analysis of Defective Interconnections of the 13 kA LHC Superconducting Bus Bars

The interconnections between Large Hadron Collider (LHC) main dipole and quadrupole magnets are made of soldered joints of two superconducting cables stabilized by a copper bus bar. The 2008 incident revealed the possible presence of defects in the interconnections of the 13 kA circuits that could lead to unprotected resistive transitions. Since then thorough experimental and numerical investigations were undertaken to determine the safe operating conditions for the LHC. This paper reports the analysis of experimental tests reproducing defective interconnections between main quadrupole magnets. A thermo-electromagnetic model was developed taking into account the complicated sample geometry. Close attention was paid to the physical description of the heat transfer towards helium, one of the main unknown parameters. The simulation results are reported in comparison with the measurements in case of static He I cooling bath. The outcome of this study constitutes a useful input to improve the stability assessment of the 13 kA bus bars interconnections.

Numerical Simulation of the Effect of Feedstock Shape on Continuous Extrusion Process

Since the appearance of the continuous extrusion process, the section shape of the feedstock is round. The shape of the feedstock directly affects metal deformation and metal flow characteristics during the continuous extrusion process. Based on finite element method (FEM), using the Deform-3D software, this paper simulates continuous extrusion forming process for copper bus bar, and analyzes the effect of different feedstock shape on metal flowing temperature, velocity, rotating torque. The results show that: the size of the rectangular feedstock must be within a reasonable range, otherwise the continuous extrusion process can not be established; the rectangular feedstock is benefit to the flow uniformity comparing with the round feedstock; the temperature of the billet and tooling with rectangular feedstock is lower than that with round feedstock, as the feedstock width increases, the temperature decreases and the area of high temperature becomes smaller; the change of the feedstock shape and size has no effect on the extrusion wheel torque value.

Effect of the Die and Tool Structure on Continuous Extrusion Expansion Forming of Copper <sup></sup>

Continuous extrusion expansion deforming is an advanced forming process for manufacturing copper bus-bar, die and tool structure is important effect factor of deformation. Based on the characteristics of the forming process, the model of rigid-plastic finite element (FE) on DEFORMT is established and the numerical simulation of continuous extrusion expansion forming process of the copper bus-bar is carried, The metal flow regularity and the mean-square deviation of velocity (SDV) with the different structure of expansion chamber and port hole and die assembled pattern is analyzed. The result show that when using the drum expansion chamber, the trapezium of port hole without transition surface and the die fitted in reverse, the variance of flow velocity is the minimum and deformation is the most homgeneous, the SDV is 0.62. The simulation results provide a theoretical direction for optimization design of die and tool structure of the continuous extrusion expansion forming. Keywords: copper bus-bar, continuous extrusion expansion deforming, die and tool structure optimization, numerical simulation

Thermal Runaways in LHC Interconnections: Experiments

The incident in the LHC in September 2008 occurred in an interconnection between two magnets of the 13 kA dipole circuit. This event was traced to a defect in one of the soldered joints between two superconducting cables stabilized by a copper busbar. Further investigation revealed defective joints of other types. A combination of (1) a poor contact between the superconducting cable and the copper stabilizer and (2) an electrical discontinuity in the stabilizer at the level of the connection can lead to an unprotected quench of the busbar. Once the heating power in the unprotected superconducting cable exceeds the heat removal capacity a thermal run-away occurs, resulting in a fast melt-down of the non-stabilized cable. We have performed a thorough investigation of the conditions upon which a thermal run-away in the defect can occur. To this aim, we have prepared heavily instrumented samples with well-defined and controlled defects. In this paper we describe the experiment, and the analysis of the data, and we summarize the main results which are relevant to delimit the conditions of safe operation for the LHC. The results obtained, and specifically a controlled replica of the September 2008 incident demonstrate the necessity to re-work all main-circuit interconnects in the LHC in order to operate safely at the nominal energy.

Investigation of residual stress in a bent Ti-clad Cu bus-bar by neutron diffraction and finite element modelling

Titanium-clad copper bus-bars are used to provide corrosion resistance in high temperature electrolytic cells. When cold-formed, such components will have a complex residual stress pattern. We report the investigation of residual stress in a high conductivity Cu bus-bar clad with Grade-2 Ti by neutron diffraction and finite element modelling. Straight bars were co-extruded, air-cooled and cold-stretched. The bars were cold-bent into an inverted ‘top-hat’ shape with four 90° bends. Residual stresses were investigated at the apex of a 90° bend. Three sets of measurements were performed in each of the measurement directions (transverse, normal and axial, relative to the straight bar): one set along the centre line in Cu; one set along the edge in Cu and one set along the edge in Ti. Residual stresses were then calculated in the three directions assuming both materials are elastically isotropic. The cooling, stretching and bending processes were simulated with an explicit finite element program, while the spr...

Environmental impacts of building materials and building services components for commercial buildings in Hong Kong

The growing concerns over the environmental impacts of buildings have led to increasing demands for more environmental friendly buildings and building materials. Hitherto, there are not any comprehensive studies that show the overall environmental impact profiles of building materials and building services components for buildings. This paper intends to bridge this gap by reporting overall lifecycle environmental profiles of buildings as well as the ranking orders of environmental impacts of all the building materials and building services materials and components for commercial buildings. Twenty-five commercial buildings in Hong Kong, which include three Grade A office buildings, four Grade B office buildings, one Grade C office buildings, four retail centers and three hotels, have been selected for our study. Based upon these collected samples, no statistical differences were found in the average lifecycle environmental impacts for different building types despite some minor variations were detected. Subsequently, 10 types of building materials and 10 types of building services components have been identified for their significant lifecycle environmental impacts on commercial buildings. Among all, concrete, reinforcement bar, copper power cables, and copper busbars were ranked to be the four most significant materials or components to the total lifecycle environmental impacts. These should form the major targets for improvements in environmental performance of commercial buildings.

Eddy Current Heating in Micro-SMES Bus-Bars

Results from numerical models and theoretical analyses are presented that describe the development of eddy current heating in copper bus bars, both with and without superconducting elements, in response to the rapid decay of current in a nearby superconducting magnet such as in micro-SMES systems. The analysis differs from those available in the open literature in that the change of magnetic field is neither instantaneous, nor sinusoidal. We especially investigate eddy current heating in the regime where the field decay time is on the order of the current diffusion time constant. It is found that the self-inductance of the copper bus bar contributes significantly to the time dependent heat generation. Analytical results are compared to experimental data in the form of subsequent temperature excursions of a liquid helium cooled copper bus, in response to field ramp rates on the order of 1.5 tesla/second.

Characteristic evaluation of electromagnetic flow couplers using a liquid metal MHD analysis code

It is known that electromagnetic flow couplers have high efficiency. In fact, an experiment using a small-scale annulus model shows that it has the maximum efficiency of 60%. However, another experiment using a middle-scale sector model exhibits that the maximum efficiency is less than 20%. In order to analyze this discrepancy, a computer code for solving magnetohydrodynamic flows is developed and is applied to the evaluation of these experiments. The obtained results show that the efficiency of the small-scale annulus model is high as observed in the experiment and the low efficiency observed in the middle-scale sector model is ascribed to the energy loss due to the eddy current arising in the ends of the magnetic region and the electric contact resistance between the stainless steel duct and the copper bus bar.

Evolutionary algorithm based approach to impedance design

Bus bars of complex cross section were designed in order to achieve desirable characteristics for use with high power switching devices. High permeability material was introduced between the copper bus bars, to increase non-linear rise of the bars' resistance with frequency. Micro genetic algorithm (?GA) was used to search for the most suitable combination of parameters. The main goal was to design bus bars with adequately adapted resistance and inductance at 10 kHz and 50 Hz simultaneously. The frequency dependant resistance and inductance were calculated utilizing 2D FEM software.

Hot-Cell Shielding System for High Power Transmission in DUPIC Fuel Fabrication

This paper presents a newly designed hot-cell shielding system for use in the development of DUPIC (Direct Use of spent PWR fuel In CANDU reactors) fuel at KAERI (Korea Atomic Energy Research Institute). This hot-cell shielding system that was designed to transmit high power to sintering furnace in-cell from the out-of-cell through a thick cell wall has three subsystems - a steel shield plug with embedded spiral cooling line, stepped copper bus bars, and a shielding lead block. The dose-equivalent rates of the hot-cell shielding system and of the apertures between this system and the hot-cell wall were calculated. Calculated results were compared with the allowable dose limit of the existing hot-cell. Experiments for examining the temperature changes of the shielding system developed during normal furnace operation were also carried out. Finally, gamma-ray radiation survey experiments were conducted by Co-60 source. It is demonstrated that, from both calculated and experimental results, the newly designed hot-cell shielding system meets all the shielding requirements of the existing hot-cell facility, enabling high power transmission to the in-cell sintering furnace.

Adhesion of Copper Electroplated to Thin Film Tin Oxide for Electrodes in Flat Panel Displays

The performance of large area and high resolution flat panel displays is contingent upon the conductivity of the transparent electrodes. Copper busbars plated to the sidewalls of the conventional electrode structure provide an order of magnitude enhancement in electrode conductivity while minimizing the loss in transmittivity to less than 3%. Essential to the above is sufficient adhesion between the copper and the . Previous work identified the need for an electrolytic reduction process, before copper plating, for adhesion to reach an acceptable strength, as observed by qualitative rubbing and peel tests. In this work, the electrochemical process conditions required for an adhesion strength of at least 100 kg/cm2 are identified. Our results show that while both the current density and the electrical charge should be carefully chosen for optimum copper layer properties, the parametric selection can be made from a relative wide range of values. The suitable charge QR, QCu (C/cm2) and current densities JR, JCu (mA/cm2) for the reduction and copper plating stages of the process are: , and . Under these conditions, the copper thickness is between 300 and 500 nm.