| 摘要 |
<p>PURPOSE:To make it possible to control arc current in a continuous and stabilized manner by providing a level detection means for a speed control signal, a speed compensation means to and a compensation signal to a speed reference output signal, and a control means to control a rise and fall in an electrode in the continuous mode. CONSTITUTION:When a level detection means 14, which detects a level of a speed control signal P, which is an output of an in-furnace resistance calculation means 5, judges whether or not the output P exceeds 5%. For example, when it judges that the output P exceeds 5% as a result of a sudden change in resistance induced by a conditional change or voltage fluctuations in a high voltage initial power receiving system, it outputs an OFF signal and turns off a gate circuit 15. Since it exceeds a dead band in this case, the output of the in-furnace resistance calculation means 5 is gain-controlled and then the controlled value enters an electrode lift control means 9 as it is so that the rise and fall of an electrode rod 18 may be continuously controlled. When it is within the dead band region, it is possible to inhibit fluctuations in extremely slight arc current, control the arc current so that it may be stabilized and obtain products having uniform quality by adding pulses, whose width is inversely proportional to the magnitude of electric current, to a high speed reference output signal.</p> |
