Projects / Programmes
Development of a new 5kHz welding transformer
| Code |
Science |
Field |
Subfield |
| 2.12.00 |
Engineering sciences and technologies |
Electric devices |
|
| Code |
Science |
Field |
| T190 |
Technological sciences |
Electrical engineering |
| Code |
Science |
Field |
| 2.02 |
Engineering and Technology |
Electrical engineering, Electronic engineering, Information engineering |
resitance spot welding system, 5 kHz realization , optimization, welding transformer, iron core, windings, monitoring system, silicon carbide input converter
Researchers (22)
Organisations (2)
Abstract
The middle frequency resistance spot welding systems are mainly used in the automotive industry for welding of car bodies, where high quality of welds and high reliability of the systems is demanded. They consist of a semiconductor input converter, a single phase welding transformer with one primary coil and two secondary coils, and a full-wave output rectifier connected to the transformer’s secondary coils. The welding transformers are normally mounted on the moving robotic arm. The reduction of the transformer’s mass on the one hand reduces the total moving mass of the robot which reduces the energy consumption and time required to move the welding transformer to the welding point, while on the other hand it reduces the amount of material required to produce a transformer. The final result is reduced energy demand and improved productivity in the automotive industry and reduced material demand and lower costs in production of welding transformers, which is in perfect agreement with the EU strategies regarding improved utilization of available energy and natural resources.
Demands of the automotive industry and competitors on the world marked force producers of the resistance spot welding systems to reduce the mass of welding transformers, which can be achieved by increasing operational frequency of the transformers. Nowadays, the middle frequency resistance spot welding systems are normally water cooled and operate at the frequency of 1 kHz. The existing semiconductor input converters, as well as the welding transformers, are optimized to operate at 1 kHz. These solutions cannot be used at the operating frequency of 5 kHz especially due to the substantial increase of losses in the transformer’s iron core, windings and input converter.
This project has three mean goals:
1. The first and the most important goal is the development of a new 5 kHz welding transformer, appropriate for applications in the middle frequency resistance spot welding systems. The project will focus on the design of the transformer’s iron core and windings, with the aim to minimize losses. Special attention will be paid to the modeling of the iron core and windings, which will be used to determine the welding transformer components with appropriate magnetic and electric properties, proper lamination and geometry. Based on the numerically determined optimal designs, prototypes will be manufactured as well. They will undergo extensive testing and measurements.
2. The second goal is the development of a new monitoring system for welding transformers. The monitoring system will be used to monitor the fitness of the welding transformers during their life span, changes in operational parameters, prediction of faults and maintenance planning, with the aim to improve reliability of the welding system operation. It will consist of a DSP based data acquisition and signal processing unit, measurement chains, unit for prediction of faults and required maintenance, data storage unit, and communication unit. The design, prototype manufacturing and testing of the hardware and software components, as well as the entire monitoring system, will be performed in the scope of the project. The monitoring system should be available as a standalone unit for upgrade of existing welding transformers and as a standard equipment of new welding transformers.
3. The third goal is the development of a new semiconductor input converter based on silicon carbide switching elements. Since, at the present time, the silicon carbide switching elements are extremely expensive, a low power silicon carbide input converter will be developed. Its power should be sufficient for testing of the welding transformer at no load. The developed input converter will be used to evaluate the potential of silicon carbide switching elements for their use in the input converters for 5 kHz resistance spot welding systems, with the focus on ability of silicon carbide switching elements to reduc
Significance for science
Most of electrical machines and devices operate in quasi-steady-state supplied by sinusoidal voltages for the majority of time. The methods and tools used in design and analysis of such machines and devices, like the finite element method, analysis based on equivalent and reluctance circuits as well as phasor and impedance based methods, are all adjusted to those operating conditions. However, there also exist other devices, like welding transformers inside resistance spot welding systems, where it is difficult to find any steady state or quasi steady-state operation. In order to optimize the design and operation of such devices a completely new approach is required. In order to design a new 5 kHz welding transformer, the project team members had to develop new and general methods appropriate for modelling, design, analysis and control design of welding transformers and resistance spot welding systems in general. The most important achievement of the project team members, which can be described as our contribution to the further development of science are as following: • new analytical methods suitable to calculate losses in windings of the welding transformer, valid for different shapes of conductor cross-sections and for different waveforms of supply currents, where the skin and proximity effects are considered; • new analytical methods, suitable to evaluate the losses due to the eddy currents and hysteresis losses in a thin and long strap of laminated steel; • new parametric dynamic model of a welding transformer based on a reluctance network iron core model, where space and time distribution of magnetic flux density in the iron core and magnetic excitation in the windings wound around individual parts of the iron core are considered in order to determine optimal design of the iron core and windings; • improvements of advanced hysteresis control of the resistance spot welding system, where a procedure for elimination of short supply current pulses and a new saturation detection procedure are proposed. It must be pointed out that for most of the aforementioned achievement patent applications were filled before they were published in the form of articles. The project team is without any doubt one of the world leading research teams in the field of resistance spot welding systems.
Significance for the country
The importance of the project’s results for development of Slovenia can be described as following: • new knowledge; • improvements in curriculum; • increased level of technological development; • new and improved products and improved competitiveness of industry. New knowledge: In the scope of the project a new knowledge has been developed that promotes Slovenia in the international scientific community. This knowledge has already been transferred in the production processes and products of the project beneficiary. In spite of the fact, that these solutions have been developed having resistance spot welding systems in mind, the developed knowledge and solutions can be used also to improve other industrial products, where transformers operating mostly in transient conditions, like in DC/DC converters, are used. Improvements in curriculum: The knowledge developed in the scope of the project will be included in curriculum at the graduated and postgraduated level of electrical engineering study. This will help to spread the new knowledge among the students and through them also in the industry. Increased level of technological development: The solutions developed in the project belong among the most advanced solutions in the field of resistance spot welding systems. They help to reduce the required material and energy cost per produced units of technologically advanced and improved products. Since, the welding transformers are produced in Slovenia, the results of the project also help to reduce the consumption of energy and material per produced welding transformer, increasing the energy efficiency. On the other hand, due to the optimized design and control algorithm, the energy consumption of the operating resistance spot welding systems is reduced as well, which contributes to general improvement of energy efficiency. New and improved products and improved competitiveness of industry: The results of the research project were already included in the new products of the project beneficiary. This reduced the production and operating cost of resistance spot welding systems, which made them, together with the improved control algorithm and new monitoring system, one of the most advanced resistance spot welding system. The competitiveness of the new product should increase the share on the global market, the results of which should through taxes also result in the national budget. The knowledge developed in the scope of the project should also help other industry that produces systems with DC/DC converters or special transformers, operating mostly in transients, to improve their products. This could lead to multiplication effects, new jobs and increased tax incomes.
Most important scientific results
Annual report
2011,
2012,
2013,
final report,
complete report on dLib.si
Most important socioeconomically and culturally relevant results
Annual report
2011,
2012,
2013,
final report,
complete report on dLib.si
