Overcurrent protection system
First Claim
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1. An overcurrent protection system in a d.c. circuit containing fuses for opening a circuit in response to an overcurrent condition, said system comprising:
- first fuse means serially connected in a circuit and rated at a value less than full load current;
a second fuse means connected in parallel with said first fuse means and rated at a value less than full load current; and
impedance means connected serially with said second fuse means and in parallel with said first fuse means for permitting flow through each of said first and second fuse means during steady state conditions of a substantially aliquot portion of circuit current, impeding current flow through said second fuse means during an overcurrent until vaporization of said first fuse means, and permitting thereafter substantially full overcurrent flow through said second fuse means.
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Abstract
A plurality of fuses are connected in a general parallel configuration for protecting a circuit, the fuses being serially connected with inductances of varying magnitude such that steady state current may be divided equally among the fuses permitting the use of fuses of lower rating. During an overcurrent surge, substantially the entire current overload is applied to each fuse in turn so that the total elapsed time for opening the circuit is less than with fuses alone.
19 Citations
11 Claims
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1. An overcurrent protection system in a d.c. circuit containing fuses for opening a circuit in response to an overcurrent condition, said system comprising:
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first fuse means serially connected in a circuit and rated at a value less than full load current; a second fuse means connected in parallel with said first fuse means and rated at a value less than full load current; and impedance means connected serially with said second fuse means and in parallel with said first fuse means for permitting flow through each of said first and second fuse means during steady state conditions of a substantially aliquot portion of circuit current, impeding current flow through said second fuse means during an overcurrent until vaporization of said first fuse means, and permitting thereafter substantially full overcurrent flow through said second fuse means. - View Dependent Claims (2)
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3. An overcurrent protection system for a circuit for applying direct current from a source to a load, said system comprising:
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a plurality of fuse means forming parallel paths for simultaneously carrying substantially an aliquot portion of steady state current; and impedance means selectively serially connected with a plurality of said fuse means for impeding current flow upon occurrence of overcurrent and directing substantially all of the overcurrent to each of said plurality of fuses seriatim. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10)
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11. A method of accelerating the response time to an overcurrent condition in excess of a predetermined value of load current in a d.c. system of a pair of fuses having substantially equal overcurrent response characteristics, said method comprising the steps of:
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connecting fuses each having a current limiting value less than the predetermined load current value; impeding flow of current through one of said fuses an occurrence of an overcurrent condition for rapidly vaporizing the other of said fuses; and permitting full flow of current through said one fuse after vaporization of said other fuse for rapidly vaporizing said one fuse.
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Specification