Technical characteristics of dual electrode DC electric arc furnace
March 06, 2024
The conventional AC electric arc furnace is powered by an AC power source and has four main drawbacks: unstable arc; Severe voltage flicker effect; Low electrode lifespan; The loss of refractory materials is severe. The reason for unstable arc is that the arc starts and extinguishes continuously at a frequency of 50 times per second. The hysteresis of re arc depends on the position of the electrode relative to the furnace material, the current setting value, and the atmosphere and temperature inside the furnace.
DC arc is more stable and unidirectional than AC arc, which has great benefits for heat transfer in metallurgical processes. Due to the absence of zero crossing in direct current, the stability of the arc is improved, and the interference to the power grid decreases. The method of using direct current to smelt metals in a direct current arc furnace is basically the same as that in an alternating current arc furnace. However, due to the high anode heat on the charge side, the electric heating conversion efficiency of the DC electric arc furnace is high.
In a dual electrode DC electric arc furnace, an arc is generated between the two electrodes and the furnace material. The rectifier power supply adopts a thyristor type inverter to convert AC power into DC power. With the help of a high current circuit and dual electrodes, electrical energy is transported to the furnace, so there is no need to set bottom electrodes.
In order to limit the dynamic short-circuit current, a DC reactor is connected in series on the DC side of the inverter. If there is no DC reactor, the dynamic short-circuit current may exceed twice the static rated current.
There are basically two types of DC power supply systems for DC arc furnaces, one is an uncontrolled rectifier type static converter, and the other is a controllable thyristor type static converter. Although the former has many advantages in terms of price, the latter has significant advantages in terms of technical performance and indicators.
DC electric arc furnace has extremely low flicker effect, not only because the arc is very stable, but also due to the influence of controllable silicon DC power supply. Because each rectifier circuit is a three-phase load. When a pair of electrodes in a DC electric arc furnace are working, all three phases can be considered to be working under the same conditions for the power supply network.
The level of noise generated by an electric arc furnace is related to the stability of the arc. Measure the noise of AC and DC electric arc furnaces under the same operating conditions. The noise of DC electric arc furnace is 15-20dB lower than that of AC electric arc furnace.
In a DC arc furnace, there is no reactance in the DC main circuit, so there is no reactance loss. In addition, due to the stability and continuity of the DC arc, the melting time is shortened, resulting in a reduction in the consumption of electrical energy. According to on-site testing and comparison, DC electric arc furnaces save 15-20% electricity compared to AC electric arc furnaces with the same capacity and conditions.
