GB757143A - Electric supply system for electrolytic grinding - Google Patents

Abstract

757,143. Automatic control systems for electrolytic grinders. BOART PRODUCTS SOUTH AFRICA, Ltd. May 17, 1954 [Sept. 21, 1953], No. 14402/54. Class 38 (4). [Also in Group XXXVI] The D.C. supply to an electrolytic grinder is controlled (a) so as to maintain a maximum current without arcing or sparking, and (b) to prevent the electrode voltage rising on opencircuit. The diamond-loaded grinding-wheel and workpiece, Fig. 1 (not shown), are immersed in an unspecified electrolyte and are supplied by lines 94 from a rectifier 456, the workpiece forming the anode. High-frequency components of the electrode current produced if arcing occurs are detected by shunt 96, amplifier 403, high pass filter 405, 406, 407, 408, and diode 410 to produce a bias voltage across potentiometer 412. The supply voltage is opposed by a reference voltage produced across a potentiometer 428 by rectifying the output of an auxiliary transformer 420. Any resultant error voltage then appears additively in series with the signal voltage tapped off potentiometer 412. An additional adjustable bias voltage is tapped off potentiometer 433. The sum of these voltages control the parallel connected pentodes 444 which control the saturation of reactors 451 in the A.C. supply to the main rectifier 456. In a modification, Fig. 2 (not shown), the voltage control is omitted, the arcing is detected by current transformer instead of a shunt, and the resulting bias signal controls reversely connected pairs of thyratrons which are in series with the A.C. supply to the main rectifier. In a further modification, Fig. 3 (not shown), the thyratrons of Fig. 2 are replaced by plasmatrons.