Current overload protection system

Claim 2

Apparatus for interrupting the continuity of an A.C. powered electrical primary circuit upon sensing a current overload therein of a duration greater than a predetermined time interval following the application of power to a load, comprising: a switch adapted to receive an electrical signal at one end thereof; first relay means disposed to provide circuit continuity in said primary circuit upon receiving a secondary signal at the winding thEreof; current sensing means disposed in inductive proximity with a conductor connected in series with the primary circuit; first SCR means operatively connected to said current sensing means to be rendered conductivee at a predetermined level of sensed current in said sensing means; second SCR means operatively connected to the other end of said switch to be rendered conductive independent of the level of said sensed current a preselected interval of time subsequent to the closing thereof; and third SCR means connected in series with said winding of said relay means and the other end of said switch including gate means operatively connected between the other end of said switch and said first and second SCR means for enabling said third SCR means to conduct concurrent with the conduction of either the first or the second SCR means and for rendering said third SCR non-conductive when both the first and second SCR means are concurrently conductive.

Claim 3

Apparatus responsive to a current overload in an A.C. circuit, comprising: current sensing means disposed in inductive proximity with the A.C. circuit for producing a first electrical gating signal indicative of the current level therein; circuit breaking means disposed in the A.C. circuit including a winding for rendering the circuit conductive upon receiving a secondary signal at said winding; switch means disposed in series with said winding for providing said secondary signal to one end of said winding at the closing thereof; first SCR means connected in series with the other end of said winding including a first gate terminal connected to said switch means for rendering said first SCR means conductive upon the closing of said switch means and receipt of said secondary signal; timing means connected to said switch means for producing a second electrical gating signal independent of the current sensed by said current sensing means a preselected interval of time subsequent to the closing of said switch means; second SCR means connected to said first gate terminal including a second gate terminal disposed to receive said first gating signal for rendering said second SCR means conductive upon receipt of said first gating signal; and third SCR means connected to said first gate means including a third gate terminal disposed to receive said second gating signal for rendering said third SCR means conductive and for shorting out said secondary signal to said first gate terminal when said second SCR means is conducting.

Claim 4

Apparatus responsive to a current overload in an A.C. circuit, comprising: current sensing means disposed in inductive proximity with the A.C. circuit for producing a first electrical gating signal indicative of the current level therein; circuit breaking means disposed in the A.C. circuit including a winding for rendering the circuit conductive upon receiving a secondary signal at said winding; switch means disposed in series with said winding for providing said secondary signal to one end of said winding at the closing thereof; first SCR means connected in series with the other end of said winding including a first gate terminal connected to said switch means for rendering said first SCR means conductive upon the closing of said switch means and receipt of said secondary signal; timing means connected to said switch means for producing a second electrical gating signal independent of the current sensed by said current sensing means a preselected interval of time subsequent to the closing of said switch means; second SCR means connected to said first gate terminal including a second gate terminal disposed to receive said first gating signal for rendering said second SCR means conductive upon receipt of said first gating signal; and third SCR means connected to said first gate means including a third gate terminal disposed to receive said second gating signal for rendering said third SCR means conductive and for shorting out said secondary signal to said first gate terminal when said second SCR means is conducting.

Claim 5

Apparatus according to claim 2, further comprising: first rectifying means disposed between said switch means and said first, second and third SCR means and said timing means for providing rectified A.C. signals thereto; and second rectifying means disposed in said current sensing means for rendering said first gating signal a rectified A.C. signal whereby said current sensing means is rendered independent of the phase and frequency of said A.C. circuit.

Claim 6

Apparatus according to claim 3, further comprising: signal smoothing means connected across said timing, current sensing and second and third SCR means for smoothing the rectified A.C. signals thereof.

Claim 7

Apparatus according to claim 4 wherein: said first, second and third SCR means include silicon controlled rectifiers.

Claim 8

Apparatus according to claim 5 wherein: said current sensing means includes temperature compensation means for maintaining said first gating signal independent of the temperature thereof.

Claim 9

Apparatus according to claim 6 wherein: said second and third SCR means are connected in parallel to said first gate terminal.

Claim 10

Apparatus according to claim 6 wherein: said second and third SCR means are connected in series.