| 摘要 |
<p>1,167,580. Automatic arc furnace control. ALLEGHENY LUDLUM STEEL CORP. Oct.17, 1967 [Oct. 17, 1966], No. 47329/67. Heading G3R. In a system for maintaining constant arc length in a consumable electrode melting furnace, first pulses are produced, dependent on some electrical characteristic of the arc, e. g. arc voltage or impedance, to which are added delayed pulses, so that if the pulses cease, which would normally cause the electrode driving motor to stop, the delayed pulses at a decreasing rate cause the electrode motion to continue downwardly, temporarily. The first pulses are passed to a circuit which generates second pulses proportional to the first pulse rate over a selected period, which first and second pulses are totalled. Means are provided for integrating the totalled pulses, also for integrating the second pulses to produce first and second signals, the difference between which controls movement of the electrode. The electrode motor may be controlled by arc voltage which is compared with a reference voltage, the error controlling a voltage to frequency converter 34 of the field effect unijunction transistor type. An alternative control, selected by a switch 40, comprises a filter 36 connected to a voltage discontinuity "hash" sensing circuit producing a pulse rate proportional to such discontinuities which may be fed to a mixer 48. The output is fed to a comparator 50 which compares pulses from the mixer 48 with those from a generator 52 - initially zero - and passes the sum through generator 52 to be added to the pulses selected by switch 40 to control the motor. On cessation of an input to mixer 48 from switch 40, the pulses from generator 52 decrease degeneratively, the run down time being longer than the expected gap in input. The delayed pulses may comprise 80% of the total.</p> |
