Separate from the furnace structure is the electrode support and electrical system, and the tilting platform on which the furnace rests. the roof, which may be refractory-lined or water-cooled, and supports the refractory delta in its centre, through which one or more graphite electrodes enter.the hearth, which consists of the refractory that lines the lower bowl.the shell, which consists of the sidewalls and lower steel ‘bowl’.The furnace is primarily split into three sections: Of the steel made today 36% is produced by the electric arc furnace route and this share will increase to 50 by 2030.Ī schematic cross-section through an EAF is presented in figure 1: three electrodes (black), molten bath (red), tapping spout at left, refractory brick movable roof, brick shell, and a refractory-lined bowl-shaped hearth. While EAFs were widely used in World War II for production of alloy steels, it was only later that electric steelmaking began to expand. The first electric arc furnaces were developed by Paul Héroult, with a commercial plant established in the United States in 1907. Pinchon attempted to create an electrothermic furnace in 1853 and, in 1878 – 79, William Siemens took out patents for an electric arc furnaces. Sir Humphrey Davy conducted an experimental demonstration in 1810 and welding was investigated by Pepys in 1815. Arc furnaces differ from induction furnaces in that the charge material is directly exposed to an electric arc, and the current in the furnace terminals passes through the charged material. The arc is established between an electrode and the melting bath and is characterized by a low voltage and a high current. 2.Electrical arc furnacesĢ.1 Construction and typical steelmaking cycleĪn electric arc furnace (EAF) transfers electrical energy to thermal energy in the form of an electric arc to melt the raw materials held by the furnace. However, sometimes it is desired to record voltage and current waveforms in the specified duration to track the disturbance levels. The total harmonic distortion (THD), short-term voltage flicker severity (Pst), and long-term voltage flicker severity (Plt) are used. In evaluation and limitation, there are some definitions and standards to quantify the disturbance levels, such as (IEC, 1999), (IEEE 1995), and (***IEEE, 1996). These currents, when circulating by the electric net can produce harmonic voltages, which can affect to other users. The Voltage-Current characteristic of the arc is non-linear, what can cause harmonic currents. Nowadays, arc furnaces are designed for very large power input ratings and due to the nature of both, the electrical arc and the melt down process, these devices can cause large power quality problems on the electrical net, mainly harmonics, inter-harmonics, flicker and voltage imbalances. In the particular case of the DC arc furnaces, the presence of the AC/DC static converters and the random motion of the electric arc, whose nonlinear and time-varying nature is well known, are responsible for dangerous perturbations such as waveform distortions and voltage fluctuations. AC and DC arc furnaces represent one of the most intensive disturbing loads in the sub-transmission or transmission electric power systems they are characterized by rapid changes in absorbed powers that occur especially in the initial stage of melting, during which the critical condition of a broken arc may become a short circuit or an open circuit. The electric arc furnaces are used for melting and refining metals, mainly iron in the steel production. Of the steel made today 36% is produced by the electric arc furnace route and this share will increase to 50 by 2030. The use of electric arc furnaces (EAF) for steelmaking has grown dramatically in the last decade. The chapter covers general issues related to power quality in Electric Arc Furnaces. Published by Horia Andrei 1, Costin Cepisca 2 and Sorin Grigorescu 2ġValahia University of Targoviste, 2Politehnica University of Bucharest, Romania
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