Overcurrent protection system with variable inverse-time characteristic
AssigneeArteche, Instrumentacion y Sistemas Electronicos, S.A.
InventorsJesus Gomez Llona, Sabino de Bernedo Melendo
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Abstract
An overcurrent protection system has an adjustable inverse-time characteristic which may be varied at will. The output of the inverse-time characteristic determining circuit is coupled to a variable timing means which is used to further shift by a predetermined time the inverse-time characteristic of the system, thereby providing a greater variety of possible switching characteristics. Further provided is an adjustable return-to-zero circuit which still further varies the characteristics of the protection system.
Claims17
An overcurrent protection system for protecting an electrical system, comprising:
- input means (1) having an input (7) for obtaining a sample of a time-varying electrical signal from the electrical system being protected and for generating a time-varying output when the input signal to said input means (1) exceeds a given value;
- generator means (3, 4) coupled to said input means (1) for selectively generating a first trip signal either immediately after receipt of the output of said input means (1) or after a first predetermined time has elapsed after receipt of the output of said input means (1), said first predetermined time being inversely proportional to the amplitude of the output of said input means (1), said generator means (3, 4) including a variable time constant means (6, 12) operating on a signal corresponding to said output signal of said input means (1) for varying the inverse-time characteristic of said generator means;
- variable timing means (5) responsive to said first trip signal generated by said generator means (3, 4) for generating a second trip signal after a second predetermined time elapses after receipt of said first trip signal, thereby shifting in time the inverse-time characteristic of said generator means;
- and
- means responsive to said second trip signal for indicating that said input to said input means (1) has exceeded said given value.
Dependencies are inferred from the claim text.