US 3,932,791 A · Multi-range, high-speed A.C. over-current protection means including a static switch

Abstract

An electronic circuit breaker for use in A.C. power circuits is provided with means for varying the overload current response level at which the circuit breaker removes power from the load. The load current is conducted through a primary winding of a transformer, and a circuit breaker switch is responsive to voltage across the secondary winding of the transformer exceeding a predetermined magnitude corresponding to the selected overload current level to remove power from the load. A lockout circuit prevents reapplication of power other than by a manual reset switch. The overload current response level corresponding to the predetermined magnitude of the voltage across the secondary winding is variably selected by varying the inductive coupling between the primary winding and the secondary winding. The primary winding is wound about one leg of a magnetic core and the secondary winding is wound about another leg of the magnetic core. In one embodiment, the inductive coupling is varied by altering a reluctance gap between the first and second legs of the core. In another embodiment, the inductive coupling is varied by changing the effective reluctance of a third leg of the core in parallel magnetic circuit with the first and second legs of the core. Both means for varying the gap and means for varying the effective reluctance of a third leg of the core may be combined to provide different ranges of selectibility. The overload current response level may also be adjusted by varying a reluctance gap in the first leg of the transformer core.

Claims8

Dependent claims

In an electronic circuit breaker having semiconductor switch means connectible between a source of power and a load for removing power from the load when current therethrough exceeds a selected overload level, a circuit for selectively varying said overload response level, comprising:

a transformer having a primary winding connected in series with said semiconductor switch and a secondary winding inductively coupled with said primary winding, a voltage being developed across said secondary winding directly proportional to the current through said primary winding and semiconductor switch, the proportional factor depending upon the inductive coupling between the primary and secondary winding;
a switch control circuit responsive to the voltage developed across said secondary winding exceeding a predetermined magnitude to cause said semiconductor switch to assume a nonconductive state, thereby removing power from the load;
and
means associated with said transformer manually operable to selectively vary the inductive coupling between the primary winding and the secondary winding whereby the overload level corresponding to said predetermined voltage magnitude across the secondary winding may be selectively varied, said inductive coupling varying means including
a magnetic core for said transformer having a first leg around which the primary winding is wound, a second leg around which the secondary winding is wound in parallel magnetic circuit with said first leg, and a third leg in parallel magnetic circuit with said first and second legs,
a control winding wound around said third leg and closed upon itself through a variable resistor for varying the effective reluctance of said third leg, and
means for varying the reluctance of one of said first and second legs including a reluctance gap in one of said first and second legs and means for selectively varying said gap.

4 more elements

In an electronic circuit breaker having a semiconductor switch means connectible between a source of power and a load for removing power from the load when the current therethrough exceeds a selected overload level, a circuit for selectively varying said overload level, comprising:

a transformer having a primary winding connected in series with said semiconductor switch and a secondary winding inductively coupled with said primary winding, a voltage being developed across said secondary winding directly proportional to the current through said primary winding and semiconductor switch;
means for controlling said switch including
means for applying trigger signals to the semiconductor switch to render it conductive,
trigger disabling means connected with said secondary winding means for disabling said trigger signal applying means when the voltage developed across the secondary winding is greater than a predetermined magnitude corresponding to the selected overload level to disconnect power from the load,
lockout means responsive to said semiconductor switch assuming a nonconductive state to maintain the voltage across said secondary winding above said predetermined magnitude, said trigger signal applying means thereby being kept disabled;
and
means associated with said transformer operable to vary the inductive coupling between the primary winding and the secondary winding whereby the overload level at which power is removed may be selectively varied.

4 more elements

Dependencies are inferred from the claim text.

Multi-range, high-speed A.C. over-current protection means including a static switch

Life of this patent

Multi-range, high-speed A.C. over-current protection means including a static switch

Life of this patent

Abstract

Claims8