Electronic circuit breaker with gradual and instantaneous cutoff

Claim 2

An energizing system for an electrical motor in which electrical energy is passed to the motor through a power circuit including at least one semiconductor switch regulated by a firing circuit, comprising a control circuit which includes an input circuit connected to receive a first signal related to the level of current flow through the motor and to combine said first signal with a reference signal to produce a resultant input signal indicating the amount by which the motor current exceeds a predetermined reference level, an amplifier circuit in said control circuit connected to provide an output control signal which varies as said resultant input signal changes, a first feedback circuit coupled to said amplifier circuit to provide proportional-plus-integral operation in the response of said output control signal to a given change of said resultant signal, and means coupled to said amplifier circuit and connected to disable the firing control circuit and interrupt energization of the motor, either immediately responsive to a sudden motor overload exceeding a preestablished level, or after a delay period responsive to a sudden motor overload less than said preestablished level.

Claim 3

An energizing system as claimed in claim 1 in which said first feedback circuit comprises a capacitor coupled in series with at least one resistor, such that the proportional operation is obtained by translation of a step signal through said capacitor and the integral operation is obtained as said capacitor charges subsequent to passage of the step signal.

Claim 4

An energizing system as claimed in claim 1 in which said first feedback circuit is a negative feedback circuit for gradually changing the output control signal from a positive level toward a negative level, and a second feedback circuit is provided and coupled to said amplifier circuit such that said second feedback circuit provides positive feedback after said output control signal goes negative.

Claim 5

An energizing system as claimed in claim 1 in which said means for disabling the firing control circuit comprises a diode coupled to the output side of said amplifier circuit to conduct when said output control signal goes negative, and a semiconductor switch coupled to said firing circuit for regulation by an inhibit signal provided when said diode conducts to disable the firing circuit.

Claim 6

An energizing system for an electrical motor in which electrical energy is passed to the motor through a power circuit including at least one semiconductor switch regulated by a firing circuit, comprising a control circuit including an operational amplifier having first and second input connections and an output connection, an input circuit connected to receive a first signal related to the level of current flow through the motor and to combine said first signal with a reference signal to produce a resultant input signal indicating the amount by which the motor current exceeds a predetermined reference level, means for applying said resultant input signal to the first input connection of the operational amplifier to provide an output control signal at said output connection which varies as a function of said resultant input signal, a first feedback circuit including a capacitor and a resistor coupled between said output connection and said second input connection of the operational amplifier to provide proportional-plus-integral operation in the response of said output control signal to a given change of said resultant input signal, and means, including a first diode, coupled between said output connection of the operational amplifier and said firing circuit, for disabling the firing circuit and interrupting energization of the moor responsive to a change in state of conduction of said first diode, which change in state occurs either immediately responsive to a sudden motor overload as signified by said resultant input signal exceeding a preestablished level, or occurs after a time delay period during which said capacitor is first charged responsive to a sudden motor overload signified by a change in said resultant input signal to a level less than said preestablished level.

Claim 7

An energizing system for an electrical motor in which electrical energy is passed to the motor through a power circuit including at least one semiconductor switch regulated by a firing circuit, comprising a control circuit including an operational amplifier having first and second input connections and an output connection, an input circuit connected to receive a first signal related to the level of current flow through the motor and to combine said first signal with a reference signal to produce a resultant input signal indicating the amount by which the motor current exceeds a predetermined reference level, means for applying said resultant input signal to the first input connection of the operational amplifier to provide an output control signal at said output connection which varies as a function of said resultant input signal, a first feedback circuit including a capacitor and a resistor coupled between said output connection and said second input connection of the operational amplifier to provide proportional-plus-integral operation in the response of said output control signal to a given change of said resultant input signal, and means, including a first diode, coupled between said output connection of the operational amplifier and said firing circuit, for disabling the firing circuit and interrupting energization of the moor responsive to a change in state of conduction of said first diode, which change in state occurs either immediately responsive to a sudden motor overload as signified by said resultant input signal exceeding a preestablished level, or occurs after a time delay period during which said capacitor is first charged responsive to a sudden motor overload signified by a change in said resultant input signal to a level less than said preestablished level.

Claim 8

An energizing system as claimed in claim 5 in which the output control signal of the operational amplifier is normally positive when said resultant input signal indicates the motor current is less than said predetermined reference level, in which said first feedback circuit provides negative feedback to gradually modify the output control signal toward a polarity reversal and effect conduction of said first diode, and a positive feedback circuit including a second diode coupled between said output connection and said first input connection of the operational amplifier, which second diode also conducts as said output control signal goes negative and thus provides positive feedback to reinforce the switching action of the control circuit including the operational amplifier.

Claim 9

An energizing system as claimed in claim 6 and further comprising a third diode, coupled between ground and a connection of said first feedback circuit, such that said third diode conducts as said output control signal goes negative and the switching action occurs, for effectively disabling said first feedback circuit as the switching of the control circuit occurs.

Claim 10

An energizing system as claimed in claim 5 and further comprising a relay having a winding and at least one contact set, means including a semiconductor switch for completing a path for current flow through the relay winding after said first diode conducts to disable the firing circuit, and circuit means, including said contact set, coupled to said capacitor in the first feedback circuit for rapidly returning the charge on said capacitor to its initial condition and thus preparing the first feedback circuit for immediate proportional-plus-integral operation as the control circuit is reset.

Claim 11

An energizing system as claimed in claim 8 in which said relay includes an additional contact set connected to interrupt the power circuit between said one semiconductor switch and the motor responsive to energization of the relay, such that the normal energizing time of the relay delays interruption of the power circuit by said additional contact set until a time after the first diode has conducted and disabled the firinG circuit.

Claim 12

An energizing system for DC electrical motor in which a power circuit includes at least one semiconductor switch regulated by a firing circuit to rectify received AC energy and provide DC energy for the motor, comprising a control circuit including an operational amplifier having first and second input connections and an output connection, an input circuit connected to receive a first signal related to the level of current flow through the motor and to provide an adjustable reference signal, means for combining said first signal and said reference signal to produce a resultant input signal indicating the amount by which the motor current exceeds a predetermined reference level, means for applying said resultant input signal to the first input connection of the operational amplifier to provide an output control signal at said output connection which is normally positive and varies in a negative-going sense as said resultant input signal increases, a negative feedback circuit including a capacitor and a resistor coupled between said output connection and said second input connection of the operational amplifier to provide a proportional-plus-integral change of said output control signal for a given step change of said resultant input signal, means, including a first diode, coupled between said output connection of the operational amplifier and said firing circuit, for disabling the firing circuit and interrupting energization of the motor responsive to a polarity change as the output control circuit goes negative and the first diode begins to conduct, which polarity change occurs virtually instantaneously responsive to a sudden motor overload as signified by a large step change in said resultant input signal exceeding a preestablished level which is passed through said capacitor to produce the switching action without capacitor charging, or which polarity change occurs after a time delay period by reason of a smaller motor overload producing a smaller step change in the resultant input signal which is passed through said capacitor and then augmented as the capacitor is charged to the level which provides the switching action, and a positive feedback circuit, including a second diode coupled between the output connection and first input connection of the operational amplifier, which conducts responsive to said polarity change to enhance the rapid switching action of the control circuit.

Claim 13

An energizing system for DC electrical motor in which a power circuit includes at least one semiconductor switch regulated by a firing circuit to rectify received AC energy and provide DC energy for the motor, comprising a control circuit including an operational amplifier having first and second input connections and an output connection, an input circuit connected to receive a first signal related to the level of current flow through the motor and to provide an adjustable reference signal, means for combining said first signal and said reference signal to produce a resultant input signal indicating the amount by which the motor current exceeds a predetermined reference level, means for applying said resultant input signal to the first input connection of the operational amplifier to provide an output control signal at said output connection which is normally positive and varies in a negative-going sense as said resultant input signal increases, a negative feedback circuit including a capacitor and a resistor coupled between said output connection and said second input connection of the operational amplifier to provide a proportional-plus-integral change of said output control signal for a given step change of said resultant input signal, means, including a first diode, coupled between said output connection of the operational amplifier and said firing circuit, for disabling the firing circuit and interrupting energization of the motor responsive to a polarity change as the output control circuit goes negative and the first diode begins to conduct, which polarity change occurs virtually instantaneously responsive to a sudden motor overload as signified by a large step change in said resultant input signal exceeding a preestablished level which is passed through said capacitor to produce the switching action without capacitor charging, or which polarity change occurs after a time delay period by reason of a smaller motor overload producing a smaller step change in the resultant input signal which is passed through said capacitor and then augmented as the capacitor is charged to the level which provides the switching action, and a positive feedback circuit, including a second diode coupled between the output connection and first input connection of the operational amplifier, which conducts responsive to said polarity change to enhance the rapid switching action of the control circuit.