Proportional firing circuit
AssigneeWolf Engineering Corporation
InventorRoger A. Holtslander
Life of this patent
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Abstract
A relay control circuit which is capable of reliably controlling the transmission of electrical power in very small time increments. Specifically, the present invention features a proportional firing circuit which will create an SCR firing signal whose pulse timing is proportional to the magnitude of a variable input signal. The control circuit varies the conduction time for the SCRs by varying the time between firing signal pulses of fixed duration.
Claims13
In an electrical switching apparatus having semiconductor controlled rectifier means for controlling the transmission of electrical power from an alternating power supply, a proportional firing circuit comprising:
- input means for providing a variable signal whose magnitude is used to control the conduction of said semiconductor controlled rectifier means;
- timer means for generating a firing signal for said semiconductor controlled rectifier means whose pulse timing is proportional to the variable characteristic of said variable signal, so as to enable the conduction time of said semiconductor controlled rectifier means to be proportionally varied between a minimum conduction time which is associated with the cycling of said alternating power supply and a maximum conduction time;
- and
- zero crossing means receiving said firing signal of said timer means for permitting the conduction of said semiconductor controlled rectifier means only at zero crossing junctions in the alternating cycle of said power supply;
- wherein said firing signal has a fixed pulse duration, and only the time between the pulses of said firing signal is varied in response to said variable input signal.
A multi-phase electrical switching apparatus circuit, comprising:
- a pair of inverse parallel connected semiconductor controlled rectifiers for at least two phases of a multi-phase electrical power supply;
- zero crossing means connected to the gate terminals of each of semiconductor controlled rectifier pairs for permitting the conduction of said semiconductor controlled rectifiers only at zero crossing junctions in the alternating cycle of said power supply;
- and
- proportional firing means for generating a firing signal for said semiconductor controlled rectifiers whose pulse timing is proportional to the magnitude of a variable input signal, so as to enable the conduction time of said semiconductor controlled rectifiers to be proportionally varied between a minimum conduction time which is associated with the cycling of said electrical power supply and a maximum conduction time;
- wherein said firing signal has a fixed pulse duration, and only the time between the pulses of said firing signal is varied in response to said variable input signal.
Dependencies are inferred from the claim text.