Magnetic Core Model of a Midfrequency Resistance Spot Welding Transformer (original) (raw)
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The objective of this paper is to analyse the performances of two controllers such as Hysteresis control (HC) and proportional integral (PI) control to control saturation level in the magnetic core of a welding transformer in a middle-frequency direct current (MFDC) resistance spot welding system(RSWS). It consists of an input converter, welding transformer, and a full-wave rectifier mounted at the transformer secondary. The unequal ohmic resistances of the two transformer's secondary circuits and the different characteristics of the diodes of output rectifier certainly lead to the magnetic core saturation which, consequently, causes the unwanted spikes in the transformer's primary current and over-current protection switch-off. The goal is to analyse the performance of both controllers in terms of transients, total harmonic distortion(THD) and variations in primary current and flux in the magnetic core of a welding transformer of highly nonlinear system of RSWS. The simulation study has been done in Matlab/Simulink environment and presented performance analysis. The responses shows that from the aforementioned aspects, proportional integral Controller is the better choice for controlling the saturation level in magnetic core of a welding transformer which is widely used in automobile industry welding system.
Engineering review, 2020
In this study, a medium frequency power transformer has been designed analytically and its sizes have been obtained. The transformer’s analyses were made numerically by 2D AnsysMaxwell Solver software package. The Solver has also helped to study suitable transformer core and winding samples. Unlike medium frequency transformer, which is generally driven by unipolar PWM method, the designed transformer is driven by bipolar PWM method in the study. The core losses were obtained for different core materials (Trafoperm N3 and Amorfous 2605SA1) by AnsysMaxwell numerical and analytical calculations. The calculated losses for no-load working conditions were compared with each other. The designed transformer has been analyzed for its noload and loaded working conditions magnetically. Finally, the radial and axial forces created in the windings have also been examined for loaded working condition.
FINITE ELEMENT ANALYSIS OF A WELDING TRANSFORMER
The study introduces the detailed sequence of operations necessary to determine the self-and mutual inductances of power transformers from numerically simulated open-circuit and bucking experiments. Parameters of a welding style transformer are compared to those of a normal step-down transformer of equivalent ratings. The investigation identifies the different patterns of magnetic flux circulation when the two transformers operate with rated load. Implications of the high reactance of welding transformers on the consumption of reactive power and power factor are analyzed.
Artificial Neural Networks - Industrial and Control Engineering Applications, 2011
elektromotorji d. o. o. Slovenia 1. Introduction This chapter deals with the detector of saturation level in the magnetic (iron) core of a welding transformer. It is based on an artificial neural network (ANN) and requires only the measurement of the transformer's primary current. The saturation level detector could be the substantial component of a middle frequency resistance spot welding system (RSWS), where the welding current and the flux density in the welding transformer's iron core are closed-loop controlled by two hysteresis controllers. The resistance spot welding systems, described in different realizations (Brown, 1987), are widely used in the automotive industry. Although the alternating or direct currents (DC) can be used for welding, this chapter focuses on the resistance spot welding system (Fig. 1) with DC welding current. The resistances of the two secondary windings R 2 , R 3 and characteristics of the rectifier diodes, connected to these windings, can slightly differ. Reference (Klopčič et al., 2008) shows that combination of these small differences can result in increased DC component in welding transformer's iron core flux density. It causes increasing iron core saturation with the high impact on the transformer's primary current i 1 , where currents spikes eventually appear, leading to the over-current protection switch-off of the entire system. However, the problematic current spikes can be prevented either passively or actively (Klopčič et al., 2008). When the current spikes are prevented actively, closed-loop control of the welding current and iron core flux density is required (Klopčič et al., 2008). Thus, the welding current and the iron core flux density must be measured. While the welding current is normally measured by the Rogowski coil (Ramboz, 1996), the iron core flux density can be measured by the Hall sensor or by a probe coil wound around the iron core. In the case, the flux density value is obtained by the analogue integration of the voltage induced in the probe coil (Deželak et al., 2008). Integration of the induced voltage can be unreliable due to the unknown integration constant in the form of the remanent flux and the drift in analogue electronic components. The drift can be kept under control by the use of closed-loop compensated analogue integrator. An advanced, the two hysteresis controllers based control of the RSWS, where the current spikes are prevented actively by the closed-loop control of the welding current and flux www.intechopen.com Artificial Neural Networks-Industrial and Control Engineering Applications
A transformer model based on the Jiles-Atherton theory of ferromagnetic hysteresis
This paper presents a transformer model that is useful for lowfrequency applications. To describe the iron-core magnetic behavior, Jiles Atherton hysteresis model is used, which is able to generate minor asymmetric loops and remanent flux. The obtained results are compared with those measured in the laboratory over a commercial resistance welding transformer.
2009
This thesis investigates optimization of the control of electrical and thermal equipment by using numerical, FEM and CFD modelling in combination with dynamic simulation models. The thesis focuses on the production of electrical strips and the control system with the aim of reducing losses and improving magnetic properties. Several parameters and factors contribute to core losses. Thickness deviations in strip production, strip's grain sizes, high levels of impurities in the core, orientation, ageing, surface oxidation, overloading, and hot spot temperature (HST) are among the reasons for losses in the core. Some of the losses occur during strip cutting and core assembly. This dissertation focuses on the reduction of losses in the cold rolling and annealing in manufacturing steps, building factor in design of core sizes and HST managing in operation stages.
Eddy-currents Modelling in Transformers Magnetic Cores Using Ohmic Resistances
11th International Conference on Environment and Electrical Engineering (EEEIC), , 2012
The inclusion of eddy-currents effects in transformers cores is a very hot subject on transformers modeling. The dominated modeling approach is based on the usage of equivalent ohmic resistances placed in the equivalent electrical circuit which represents the electrical part of the transformer. In this paper, a comparison study, between the main different models using ohmic resistances for the eddy-currents in transformers magnetic cores, is conducted. Specifically, the selection of the suitable ohmic resistance, according to the study that is going to be conducted using an appropriate transformer model, is clarified; a topic that has not sufficiently been investigated and presented in the literature. The methods for determination of the ohmic resistances, in the simple case of a single-phase core-type transformer, are presented. Corresponding numerical results are given, which are compared to measured values if possible.
The simulation of a new high frequency transformer
Journal of Energy Systems
Core losses of transformers motivate many engineers and scientists to design and implement different transformers for their specific aims. Since there exists a growing interest on high frequency applications in today’s world, design and optimization studies of a magnetic fluid core transformer (MFCT), having an easy and cheap production approach in high frequency applications, are considered in the present paper. The desired design should operate in a more efficient way within a wide frequency band. The MFCT considered here can be a solution to the eddy currents and core losses encountered in the conventional transformers with its low conductivity, oil-based magnetic fluid and super paramagnetic characteristic. The magnetic fluid in the proposed work consists of a combination of ferromagnetic particles made by iron in an averaged diameter of 70 µm with an adjustable magnetism compared to the traditional magnetic fluids and an engine oil, thereby the magnetic permeability of the over...
Finite-element-based nonlinear physical model of iron-core transformers for dynamic simulations
IEEE Transactions on Magnetics, 2000
A finite-element (FE)-based transformer physical phase variable model is proposed. In this model, the effects of nonlinear magnetization on inductances are included by considering the inductance variations with the amplitude of the ac flux as well as its phase angle during a complete ac cycle. Such a consideration is represented by 2-D inductance tables. The magnetizing currents at various magnetization levels are used to calculate the inductances then build the table. The magnetizing currents are determined using circuit-coupled FE analysis of the transformer with sinusoidal voltage supplies. The structure of the inductance table is given and the procedure of inductance table lookup during dynamic simulation is provided. Simulink implementation of the FE-based transformer phase variable model is performed. The validity of the presented technique is verified through comparing the magnetizing current waveforms obtained from the FE-based phase variable model and those from an FE model. The significance of the proposed FE-based phase variable model is in its accuracy and its applicability for dynamic simulation of interconnected components in a power system. Index Terms-Dynamic simulation, finite elements, FE-based model, phase variable, physical modeling, transformer.