Apparatus for controlling power to a load by sensing overload conditions

Claim 2

A switching circuit for controlling power to a load from a source of electrical power comprising switching means connected in series with the load across the source, means for sensing the level of current through the load, means responsive to said current sensing means for operating the switching means to interrupt the current to the load when the current level exceeds some selected level, and means responsive to said current sensing means for operating the switching means to restore current to the load after the current has been interrupted for a predetermined time interval.

Claim 3

Apparatus as defined in claim 1, further including means for sensing the voltage drop across the load, and means controlled by said voltage sensing means for reducing the effective current level at which said means operating the switching means interrupts current to the load in response to a drop in voltage across the load.

Claim 4

Apparatus as defined in claim 1 wherein said means operating the switching means to interrupt the current to the load includes means for adjusting the time required for the switching means to interrupt the current to the load inversely in relation to the magnitude of the load current in excess of selected level.

Claim 5

Apparatus as defined in claim 1, wherein the current responsive means includes a magnetic amplifier having a first bias winding connected in series with the load.

Claim 6

Apparatus as defined in claim 2, wherein the current responsive means includes a magnetic amplifier having a first bias winding connected in series with the load.

Claim 7

Apparatus as defined in claim 1, wherein the switching means includes a power transistor having collector, emitter, and base electrodes, the collector and emitter electrodes being connected in series circuit with the load, and a source of base current connected to the base and emitter electrodes for turning on the power transistor, and further including first and second transistors, each having collector, emitter, and base electrodes, the first transistor having its collector electrode connected to the collector of the power transistor and its emitter electrode connected to the base of the power transistor, the second transistor having its emitter electrode connected to the base of the power transistor and having its collector connected to the emitter of the power transistor, a resistor connecting the base electrode to the emitter electrode of each of said first and second transistors, and a resistor and capacitor in series connecting the base electrode of each of said first and second transistors to a common reference potential.

Claim 8

A switching circuit for controlling power to a load from a source of electrical power comprising switching means connected in series with the load across the source, means for sensing the level of current through the load, means responsive to said current sensing means for operating the switching means to interrupt the current to the load when the current level exceeds some selected level, means for sensing the voltage drop across the load, and means controlled by said voltage sensing means for reducing the effective current level at which said means operating the switching means interrupts current to the load in response to a drop in voltage across the load, the current responsive means including a magnetic amplifier having a first bias winding connected in series with the load, the voltage sensing means including a second bias winding in the magnetic amplifier, the second bias winding being connected in shunt across the load.

Claim 9

A switching circuit for controlling power to a load from a source of electrical power comprising switching means connected in series with the load across the source, means for sensing the level of current through the load, means responsive to said current sensing means for operating the switching means to interrupt the current to the load when the current level exceeds some selected level, means for sensing the voltage drop across the load, and means controlled by said voltage sensing means for reducing the effective current level at which said means operating the switching means interrupts current to the load in response to a drop in voltage across the load, the current responsive means including a magnetic amplifier having a first bias winding connected in series with the load, the voltage sensing means including a second bias winding in the magnetic amplifier, the second bias winding being connected in shunt across the load.

Claim 10

Apparatus as defined in claim 7, further including a source of bias voltage connected across the second bias winding.

Claim 11

A power controller circuit for switching current to a load from a direct-current source, comprising a switch element connected in series with the load across the source, means responsive to an input control signal for selectively turning the switching element on and off, and means responsive to the level of current through the load when the switch unit is turned on for interrupting the current path to the load when the peak current exceeds a predetermined level, said last-named means including means responsive to the drop in current level to the load when the current path is interrupted for restoring the current path after a predetermined time whereby the current is interrupted and restored at recycling time intervals as long as the peak load current exceeds said level. 10. Apparatus as defined in claim 9, including a timing circuit, means responsive to the level of current to the load for actuating the timing circuit when the current level exceeds a predetermined level, and means responsive to the timing circuit after a set time interval for changing said input control signal means to turn off the switching element, the time interval of said timing circuit being longer than said recycling time interval of said current interrupting means.

Claim 12

Apparatus as defined in claim 9, wherein said current interrupting means includes a magnetic amplifier driven from an alternating-current source and having a bias winding connected in series with the load, the magnetic amplifier providing an output signal in response to a high level of current through the bias winding, and means for turning off the switching unit in response to said output signal from the magnetic amplifier output.

Claim 13

A power controller for directing power to a load from a direct-current source and limiting the average current to the load, comprising a power transistor having collector, base, and emitter electrodes, the power transistor having its collector and emitter electrodes, series connected with the load across the source, a magnetic amplifier circuit including a control winding connected in series with the load and power transistor, means responsive to the output of the magnetic amplifier for periodically turning the power transistor off and on to control the average current to the load when the peak current through the control winding reaches a predetermined level, a bias winding in the magnetic amplifier, means normally passing current through the bias winding in a direction to produce magnetic opposition to the field produced by the control winding, and means for decreasing the current through the bias winding with a decrease in voltage across the load.

Claim 14

A power controller for directing power to a load from a direct-current source and limiting the average current to the load, comprising a power transistor having collector, base, and emitter electrodes, the power transistor having its collector and emitter electrodes, series connected with the load across the source, a magnetic amplifier circuit including a control winding connected in series with the load and power transistor, means responsive to the output of the magnetic amplifier for periodically turning the power transistor off and on to control the average current to the load when the peak current through the control winding reaches a predetermined level, a bias winding in the magnetic amplifier, means normally passing current through the bias winding in a direction to produce magnetic opposition to the field produced by the control winding, and means for decreasing the current through the bias winding with a decrease in voltage across the load.

Claim 15

Apparatus in claim 12, further including an alternating-current source, rectifier means coupled to said alternating-current source, the rectifier means being connected to the base of the power transistor, the magnetic amplifier being driven from said alternating-current source to provide a pulsed output from the amplifier at a rate determined by the frequency of the source.

Claim 16

Apparatus as defined in claim 13, further including a timing circuit, means responsive to the peak level of current flow through the load for turning on said timing circuit when the load current peaks exceed a predetermined level and turning off the timing circuit when the load current peaks drop below said level, and means controlled by the timing circuit for disabling the alternating-current source when the timing circuit has been on a preset time interval.

Claim 17

Apparatus as defined in claim 14, wherein said means for turning on the timing circuit iNcludes a second magnetic amplifier driven from said alternating-current source, the second magnetic amplifier having a control winding in series with the load.

Claim 18

A power controller circuit for connecting a load to a DC power source comprising a power transistor having a collector, an emitter, and a base electrode, the load being connected in series with two of said electrodes across the said source, control means for biasing said transistor into saturation to pass current from the source to the load, means for sensing the level of current through the load, means responsive to the current-sensing means for controlling the power transistor to limit the average current through the load to a predetermined maximum overload level, a timing circuit, means responsive to said current level sensing means for activating said timing circuit when the average current exceeds a predetermined level, and means responsive to the timing circuit for biasing off the power transistor after the average current level has exceeded said predetermined level for a preset interval of time.

Claim 19

A power controller circuit for connecting a load to a DC power source comprising a power transistor having a collector, an emitter, and a base electrode, the load being connected in series with two of said electrodes across the said source, control means for biasing said transistor into saturation to pass current from the source to the load, means for sensing the level of current through the load, means responsive to the current-sensing means for controlling the power transistor to limit the average current through the load to a predetermined maximum overload level, a timing circuit, means responsive to said current level sensing means for activating said timing circuit when the average current exceeds a predetermined level, and means responsive to the timing circuit for biasing off the power transistor after the average current level has exceeded said predetermined level for a preset interval of time.