Static overcurrent relay
AssigneeGeneral Electric Company
InventorDavid W. Little
Life of this patent
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Abstract
A solid state protective device is disclosed which monitors an electric quantity such as current in a protected circuit and which responds to abnormal conditions by activating a circuit breaker or warning device after a period of time which is related by a non-linear inverse function to the magnitude of the circuit quantity being monitored. The device includes a non-linear function generator, using an operational amplifier to which a relatively low bias signal is supplied, to approximate the non-linear operating characteristics of earlier electromechanical protective devices.
Claims11
A protective relay adapted to be coupled to an alternating current circuit for producing a trip signal in delayed response to the value of a circuit quantity becoming excessive, said relay comprising:
- a. means for deriving from said circuit a unipolar input signal of variable amplitude representative of said quantity;
- b. means for providing a predetermined bias signal of relatively low magnitude;
- c. function generating means to which said input signal and said bias signal are supplied in polarity opposition, said function generating means being operative to produce an output signal which varies as a non-linear function of the sum of said signals,
- d. means connected to said function generating means and operative whenever the value of said circuit quantity becomes excessive for integrating said output signal in order to produce an integrated output signal;
- and
- e. means connected to said integrating means capable of producing a trip signal if the integrated output signal exceeds a preselected level.
Dependencies are inferred from the claim text.