The control goal of the fused magnesium furnace control system is to control the temperature, and the current equipment and conditions for directly controlling the temperature cannot meet the price of the concentrate powder. 97 fused magnesia picture Since temperature is a function of electrical energy, the core part of the control is the control of the arc or current. For the control of the arc, it is the control of the current. Since the change of voltage will cause the fluctuation of the power grid to have relevant equipment, the input cost is high and the effect is not good, so the voltage of the input fused magnesium furnace remains almost constant; at the same time, due to high temperature and high current, etc., Control of the resistivity of the molten pool is also impossible. Then the method of controlling the resistance is only one way to adjust the length of the resistor. In actual production, the phase-to-phase resistance length and arc length are controlled by adjusting the relative positions of the electrodes, but the displacement of the electrodes and the length of the arc are not determined due to the uncertainty of the arc

The function relationship brings difficulty to the precise control of the current. In addition, the too frequent lifting electrode will cause the tip of the electrode to be relatively far away, and the phenomenon of arc breaking occurs. Once the arc is broken, the arc is re-ignited, which affects the normal production. In addition, the purity of the product is reduced due to the addition of the arc-ignition material, and unnecessary heat energy loss is also increased. Recently, the control strategy adopted by the control system of the fused magnesium furnace can be generally divided into three modes: constant current control, constant power control and constant impedance control.

Constant current control, as the name implies, is a constant set value of a given current. At this set value, the energy generated by the current is sufficient to meet the requirements of the crystallization of the raw material, and the input current is adjusted by the electrode to meet the setting. Fluctuations within the range of values. The advantages of constant current control are constant electrode current, stable arc, and strong resistance to grid flicker. The disadvantage is that it is difficult to ensure uniform heating, because the adjustment current does not consider the insertion depth of the electrode in the charge. The depth of the electrode and the current value are not simply linear, so it is difficult to ensure both the charge zone and the weld zone. Have proper heat distribution. However, since the constant current is easy to set and track, the adjustment is relatively simple. Therefore, this scheme is adopted by some units. For example, some manufacturers of Dashiqiao-some fused magnesia have adopted this control scheme to set the current.

The setting is set at 100011000A.

Constant power control, similar to constant current control, is a predetermined set value is power. However, the constant power control has a big disadvantage. The single-phase arc power is zero when the short circuit and the current are cut off. At this time, the action of the electrode to rise or fall cannot be calculated by the power-parameter, and must be added. Control algorithm. That is to say, even in non-special working points, there is the possibility of misoperation, especially in the case of fused magnesia furnace, the disturbance is always present,

It increases the probability of misoperation. Constant impedance control, the sensitivity of this control method is relatively high, Hengyang anti-control can be approximated as constant arc length control, and the constant resistance control referred to in the domestic fused magnesium furnace production industry is not absolutely constant. Impedance control essentially refers to the differential control of current and voltage, because the resistance value of the main circuit of the furnace varies greatly throughout the melting period, and there is a strong dependency between the main circuit impedance and the arc current. Therefore, in a typical smelting process,

A constant impedance regulator can only maintain the arc current at a medium level for the set value.