The versatility, rich mathematical formulations and robustness of finite element methods make them attractive for simulations for a wide range of problems. Two dimensional models concerning the seam welding process do have some limitations. The longitudinal two dimensional models cannot be used to examine the effects of the electrode shape and thickness regarding heat generation during the seam welding process. The transversal two dimensional models are not helpful for examining the nugget growth during the seam welding process. The heat energy generated during the seam welding process mainly depends on the resistance between the electrodes, welding current, rotational speed and the geometry of the electrodes. The settings for appropriate parameters in relation to a seam welding machine, with regards to sheets of different thicknesses, depends on trial and error methods. These methods are expensive and time consuming. The three dimensional model developed in this paper is a step towards selecting the appropriate welding parameters so as to produce a good welding nugget. 

Inverter drive resistance spot welding machines are becoming a good choice of welding because of the increased machine efficiency and output power. The DC link capacitors in spot welding equipment store a large amount of energy. In case of any failure, the IGBT in the inverter has a risk of exhibiting a violent rupture. This rupture can damage the converter, drive down time and personal injury which may lead to the machinery certification problems. IGBT failure detection and solution for protection of these failures in resistance welding machines have not been reported in literature. Literature study of the IGBT failure, rupture, fault detection and protection has been carried out for inverter drives in power applications. On the basis of the findings some protection schemes and important measures in the design of the machine have been adopted which have resulted in the reduced risk of IGBT failure.

Power supply is an inevitable component for all electronic instruments as a constant DC source. Almost all power supplies use feedback loop to achieve constant DC output voltage. In a feedback loop, the galvanic isolation is required between input and output. It can be achieved either by implementation of opto-coupler feedback on the secondary side or magnetic feedback. In this paper both opto-coupler and auxiliary feed-back techniques are implemented and analyzed in a high frequency half bridge converter using coreless Printed Circuit Board (PCB) power transformer. The implementation of opto-coupler feedback is temperature sensitive and has relatively high cost. The auxiliary winding of transformer can also be used to provide feedback signals as alternate to opto-coupler. Auxiliary feedback implementation is cheaper, temperature stable and insensitive to temperature variations. In this paper, the feasibility of feedback using auxiliary winding of coreless PCB power transformer is investigated. It is observed that this technique can be used as an alternative to opto-coupler feedback.

The higher switching frequency in combination with di/dt loops and dv/dt nodes in the power stages of high frequency power converters generates higher order harmonics which cause Electro Magnetic Interference (EMI). It is commonly perceived that high frequency converters are more vulnerable to radiated EMI, thus, it is very important to analyze the radiated emission of these converters. According to the author’s knowledge, the analysis of the radiated emission of power converters switching in the MHz frequency region has not been presented until now. Therefore, in this paper, the measurements, and analysis of the near field radiated emissions of these emerging power converters is presented. These measurements are beneficial in the early design stage of power converters. Both E-field and H-field and captured and analyzed for a half bridge converter switching at 3 MHz and at the output power level of 25 W. The effects of the magnetic and electric field emissions with the addition of a Y-capacitor and secondary side common mode choke are analyzed.

Electromagnetic effects influence the design of power converters switching in MHz frequency region. In these converters, the high switching frequency in combination with sudden changes in current and voltage levels generate higher order harmonics which causes Electro Magnetic Interference (EMI). To study the effects of increased switching frequency on conducted EMI, the harmonics amplitudes are analyzed by increasing the switching frequency of a two wire input half bridge power converter from 1.32 MHz to 3 MHz. In order to suppress the Common Mode (CM) conducted EMI, different possibilities of connecting the Y- capacitor in a two wire universal input half bridge converter are discussed and the conducted EMI is measured and analyzed by connecting the Y- capacitor at different points. The line filters are designed, characterized and implemented in order to suppress conducted EMI. The effects of increased switching frequency on the line filter design are studied by analysing the EMI spectrum of both the converters. The analysis of results indicates that the filter size is reduced by increasing the switching frequency of the power converter. 

The fabrication of emerging power semiconductor devices and high frequency PCB power transformers has made it possible to design the power converters in MHz switching frequency range. However, the higher switching frequency, di/dt loops and dv/dt nodes in power stages of these converters generate higher order harmonics which causes Electro Magnetic Interference (EMI). It is commonly believed that the EMI has worst affect in the converters switching in MHz frequency range than the converters operating below 150 kHz. Thus, it is important research direction to investigate the consequences of implementing a line filter to suppress the conducted EMI in high frequency power converters. In this paper, the measurements, and analysis of the conducted EMI in emerging power converters, switching in MHz frequency range, and the design of the filter for its suppression is presented. The design of LISN and its PCB implementation for EMI measurements is presented. The measurement of conducted EMI of a half bridge DC-DC converter switching at          3.45 MHz and the analysis of the frequency spectrum is discussed. The design, PCB implementation and characterization of the EMI filter and the measurement of the suppressed conducted noise by applying the filter are also discussed.

With the emerging power semiconductor devices in GaN and SiC technology and the development of high frequency multilayered PCB power transformers, power efficient DC-DC converters are designed in megahertz switching frequency range. The increased switching frequency in combination with sudden changes in current “di/dt” or voltage “dv/dt” levels generate higher order harmonics, which cause Electro Magnetic Interference (EMI). One of the major challenges, to design the power stage of these converters, is to minimize the EMI because it affects their Electro Magnetic Compatibility (EMC). There is a spread belief that the EMI becomes much worse in a MHz switching converter compared to the current ones operating below 150 kHz. This paper investigates the consequences on implementation of a line filter for suppressing conducted EMI in high frequency power converters. The results are based on electronic simulations, comparing EMI and filter design, for a 200 kHz and 2 MHz buck converter under similar conditions. By analyzing the noise frequency spectrum of both the converters it is observed that the size of filter components, such as capacitors and common mode chokes is greatly reduced in case of 2MHz Buck converter. The results show that the size reduction that can be accomplished by increasing the switching frequency to MHz range can be improved further by a smaller implementation of the line filter as well.

Resistance spot welding process comprises of electric, thermal and mechanical phenomenon, which makes this process complex and highly non-linear and thus, it becomes difficult to model it. In order to obtain good weld nugget during spot welding, hit and trial welds are usually done which is very costly. Therefore the numerical simulation research has been conducted to understand the whole process. In this paper three different cases were analyzed by varying the tip contact area and it was observed that, with the variation of tip contact area the nugget formation at the faying surface is affected. The tip contact area of the welding electrode becomes large with long welding cycles. Therefore in order to maintain consistency of nugget formation during the welding process, the current compensation in control feedback is required. If the contact area of the welding electrode tip is reduced, a large amount of current flows through the faying surface, as a result of which sputtering occurs.