Abstract A DEVICE FOR DETECTING UNBALANCED CURRENT FLOW IN THE CONDUCTORS OF A POWER SUPPLY CIRCUIT AND DEENERGIZING THE CIRCUIT UPON PREDETERMINED CONDITIONS OF UNBALANCE. A DIFFERENTIAL TRANSFORMER IS EMPLOYED WHICH HAS A MULTIPLE-TURN SECONDARY WINDING, THE PRIMARY WINDINGS BEING FORMED BY THE CONDUCTORS OF THE POWER SUPPLY CIRCUIT. THE OUTPUT FROM THE DIFFERENTIAL TRANSFORMER CONTROLS THE CURRENT FLOW THROUGH A DETECTOR TRANSISTOR. A REFERENCE TRANSISTOR, SIMILAR TO THE DETECTOR TRANSISTOR, IS CONNECTED SO THAT ITS CURRENT FLOW IS CONTROLLED BY EXTERNAL MEANS. THE VOLTAGES PRODUCED BY THE CURRENT FLOWS THROUGH THE TWO TRANSISTORS ARE COMPARED BY A COMPARATOR CIRCUIT WHICH PRODUCES A TRIPPING SIGNAL UPON A PREDETERMINED UNBALANCE OF THE CURRENTS. CIRCUIT BREAKER MEANS IN THE POWER SUPPLY CIRCUIT IS RESPONSIVE TO THE TRIPPING SIGNAL TO DEENERGIZE THE LOAD. BY EMPLOYING TWO TRANSISTORS, COMMON TEMPERATURE EFFECTS ARE SUBSTANTIALLY CANCELED OUT.
The device of claim 1 wherein said current control devices are transistors.
Claim 2
Dependent Claim
103 words
A circuit protective device which comprises: a differential transformer; a transistor having its base connected to the secondary winding of said differential transformer, said differential transformer and transistor being responsive to current unbalance in at least two conductors of a protected circuit to produce a first electrical signal proportional thereto; means for producing a second electrical signal substantially independent of said first signal; means for comparing said first and second electrical signals to produce an output signal responsive to a differential relationship therebetween; and means responsive to said output signal to interrupt said protected circuit at a preselected value of said output signal.
Claim 3
Dependent Claim
101 words
A circuit protective device which comprises: means responsive to current unbalance in at least two conductors of a protected circuit to produce a first electrical signal proportional thereto; means for producing a second electrical signal substantially independent of said first signal; means for comparing said first and second electrical signals to produce an output signal responsive to a differential relationship therebetween; an integrating capacitor connected to be charged in response to said output signal; and relay means responsive to the charge on said integrating capacitor to open at least one of said conductors at a preselected value of said output signal.
Claim 4
Dependent Claim
139 words
A circuit protective device which comprises: means responsive to current unbalance in at least two conductors of a protected circuit to produce an electrical error signal proportional thereto; a DC power supply; a detector transistor having its emitter-collector circuits across said power supply; means applying said electrical error signal to the base of said detector transistor; a reference transistor having its emitter-collector circuit across said power supply; means applying a reference signal to the base of said reference transistor, whereby current flow through the emitter-collector circuits of the respective detector and reference transistors establishes first and second electrical signals; means for comparing said first and second electrical signals to produce an output signal responsive to a differential relationship therebetween; and means responsive to said output signal to interrupt said protected circuit at a preselected value of said output signal.
Claim 5
Dependent Claim
16 words
The device of claim 5 wherein said means responsive to current unbalance comprises a differential transformer.