| 摘要 |
1,106,805. Protective arrangements. STARKSTROM-ANLAGENBAU ERFURT. 10 Sept., 1965, No. 38716/65. Heading H2K. An overcurrent protective arrangement for an A.C. circuit has a Schmitt trigger 8 which shapes the input current into pulses each having a duration dependent on the magnitude of the input current. These pulses are applied to a monostable circuit 12 and a negator 9, both connected to an OR element 15. When the pulse duration is sufficiently long, the monostable circuit 12 changes to its unstable stable and this circuit 12 and the negator 9 both apply an O signal to the element 15, so that a further negator 16 connected to the OR element 15 provides a 1 signal on each pulse. The frequency of these pulses is reduced by a frequency divider and the resulting pulses are applied to counting stages so that after a predetermined number of pulses a tripping circuit is energized, Fig. 2 (not shown). The negator 16 may also control an indicator 19 through a bi-stable circuit 17 and amplifier 18. A further monostable circuit (as 12) and a further OR element (as 15) may be associated with the negator 9 for response to a longer pulse duration and to control the tripping circuit without the delay of the counting stages.
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