GB1279427A - Electrophoretic lacquering - Google Patents

Abstract

1279427 Static rectifiers SIEMENS AG 9 Oct 1969 [19 Oct 1968] 49724/69 Heading H2F [Also in Division C7] Relates to short-circuit protection in an A.C./D.C. static converter arrangement for electrophoretic lacquering plant comprising controllable rectifier units 9, 10, 11 connected between respective conveyer rails 5, 6, 7 and a dipping tank 2 and which receive firing pulses simultaneously from a common pulse unit 15 controlled in dependence upon deviations of actual A.C. input current and D.C. output voltage from desired values, by circuits 14, 13. In the event of a short-circuit between one of the rails and the tank, firing pulses to the rectifier unit connected to that rail are prevented by the opening (e.g. by overcurrent protection units, not shown) of a remotely controlled switch 31, 32 or 33 in the control lines to that rectifier unit. The circuit 13 receives a desired output voltage signal from a potentiometer 17 and actual output voltage signals via decoupling diodes 20, 21, 22. The output of circuit 13 is used as a desired current value and fed into a current controller 14. The actual input current to the rectifier units is sensed by C.T.s 28, 29, 30 and fed via diodes 24, 25, 26 to a common link, the maximum of the three currents being compared with the desired value in the circuit 14. Instead of the A.C. input currents the direct current outputs of the rectifier units may be sensed and fed back. The rectifier units may be in semi-controlled bridge configuration with a common uncontrolled bridge half, the controlled bridge halves being connected to respective conveyer rails. Each switch 31, 32 or 33 comprises a plurality of contact pairs one pair connected to each rectifier element.