C motor control system utilizing a selectively energizable semiconductor switch means

Claim 1

A system for controlling the operation of an induction motor having a start winding and a run winding comprising a first selectively energizable semiconductor current switch means having a pair of power terminals and a control terminal for controlling current flow between said power terminals, said power terminals being serially connected between the start winding and a source of power, trigger means including a first temperature-responsive element having a resistance which varies in response to the temperature thereof and being adapted for operation in a current-limiting self-heating mode coupled to said control terminal for controlling the flow of current thereto so as to control the energization of said first switch means and being adapted to conduct triggering current to said control terminal to render said first Switch means conductive for a predetermined time interval until current limiting operation thereof is initiated causing a reduction in the flow of current therethrough so as to render said first switch means nonconductive after said predetermined time interval, said first temperature-responsive element being coupled to said run winding so as to receive sufficient current subsequent to said predetermined time interval to remain operational in its self-heating mode to preclude additional current flow to the start winding during running of the motor, and means for energizing the start winding and said trigger means so as to apply triggering current to said first temperatureresponsive element to energize said switch means and permit current flow to the start winding during said predetermined time interval, thereby effecting starting of the motor.

Claim 2

A system for controlling the operation of an induction motor having a start winding and a run winding comprising a first selectively energizable semiconductor current switch means having a pair of power terminals and a control terminal for controlling current flow between said power terminals, said power terminals being serially connected between the start winding and a source of power, trigger means including a first temperature-responsive element having a resistance which varies in response to the temperature thereof and being adapted for operation in a current-limiting self-heating mode coupled to said control terminal for controlling the flow of current thereto so as to control the energization of said first switch means and being adapted to conduct triggering current to said control terminal to render said first Switch means conductive for a predetermined time interval until current limiting operation thereof is initiated causing a reduction in the flow of current therethrough so as to render said first switch means nonconductive after said predetermined time interval, said first temperature-responsive element being coupled to said run winding so as to receive sufficient current subsequent to said predetermined time interval to remain operational in its self-heating mode to preclude additional current flow to the start winding during running of the motor, and means for energizing the start winding and said trigger means so as to apply triggering current to said first temperatureresponsive element to energize said switch means and permit current flow to the start winding during said predetermined time interval, thereby effecting starting of the motor.

Claim 3

A system for controlling the operation of an induction motor having a start winding and a run winding comprising a first selectively energizable semiconductor current switch means having a pair of power terminals and a control terminal for controlling current flow between said power terminals, said power terminals being serially connected between the start winding and a source of power, trigger means including a first temperature-responsive element adapted for operation in a current-limiting mode coupled to said control terminal for controlling the flow of current thereto so as to control the energization of said first switch means, said first temperature-responsive element being adapted to conduct triggering current to said control terminal to render said first switch means conductive for a predetermined time interval until current-limiting operation thereof is initiated causing a reduction in the flow of current therethrough so as to render said first switch means nonconductive after said predetermined time interval said first temperature-responsive element comprising a first PTC thermistor adapted for operation in a self-heating mode and being coupled to the run winding so that sufficient current is applied to said first PTC thermistor during running of the motor subsequent to said predetermined time interval to maintain said first PTC thermistor operational in its self-heating mode thereby precluding additional current flow to the start winding during running of the motor, and means for energizing the start winding and said trigger means so as to apply triggering current to said first temperature-responsive element to energize said switch means and permit current flow to the start winding during said predetermined time interval, thereby effecting starting of the motor.

Claim 4

A system for controlling the operation of an induction motor having a start winding and a run winding comprising a first selectively energizable semiconductor current switch means having a pair of power terminals and a control terminal for controlling current flow between said power terminals, said power terminals being serially connected between the start winding and a source of power, trigger means including a first temperature-responsive element adapted for operation in a current-limiting mode coupled to said control terminal for controlling the flow of current thereto so as to control the energization of said first switch means, said first temperature-responsive element being adapted to conduct triggering current to said control terminal to render said first switch means conductive for a predetermined time interval until current-limiting operation thereof is initiated causing a reduction in the flow of current therethrough so as to render said first switch means nonconductive after said predetermined time interval said first temperature-responsive element comprising a first PTC thermistor adapted for operation in a self-heating mode and being coupled to the run winding so that sufficient current is applied to said first PTC thermistor during running of the motor subsequent to said predetermined time interval to maintain said first PTC thermistor operational in its self-heating mode thereby precluding additional current flow to the start winding during running of the motor, and means for energizing the start winding and said trigger means so as to apply triggering current to said first temperature-responsive element to energize said switch means and permit current flow to the start winding during said predetermined time interval, thereby effecting starting of the motor.

Claim 11

A system for controlling the operation of an induction motor having a start winding and a run winding comprising a first selectively energizable semiconductor switch device having a pair of power terminals and a control terminal for controlling the flow of current between said power terminals in response to a triggering current, said power terminals being connected between the start winding and a source of power; trigger means, including a first PTC thermistor adapted for operation in a high-resistance, self-heating mode coupled to said control terminal for controlling the application of triggering current thereto, said first PTC thermistor being adapted to conduct current substantially in excess of said triggering current prior to the initiation of operation in its high-resistance mode so as to abruptly energize said switch device for a predetermined time interval, high-resistance operation of said first PTC thermistor being positively initiated upon expiration of said predetermined time interval effecting a reduction in the flow of current therethrough rendering said switch device nonconductive, said first PTC thermistor being coupled to the run winding to receive sufficient current during running of the motor subsequent to the predetermined time interval to maintain said first PTC thermistor in its high-resistance mode, and current-limiting means connected between said first thermistor and said switch device for limiting the current applied to said control terminal to a level sufficient to maintain said switch device conductive only until high-resistance operation of said first PTC thermistor is effected, said current-limiting means being effective to limit triggering current supplied to said control terminal when the current flow through said first PTC thermistor is reduced due to high-resistance operation thereof to effect abrupt energization of said switch device, and means for energizing the start winding and said trigger means so as to apply triggering current through said first PTC thermistor to energize said switch device, whereby current flow is effected through the start winding during said Predetermined time interval.

Claim 12

A system for controlling the operation of an induction motor having a start winding and a run winding comprising a first selectively energizable semiconductor switch device having a pair of power terminals and a control terminal for controlling the flow of current between said power terminals in response to a triggering current, said power terminals being connected between the start winding and a source of power; trigger means, including a first PTC thermistor adapted for operation in a high-resistance, self-heating mode coupled to said control terminal for controlling the application of triggering current thereto, said first PTC thermistor being adapted to conduct current substantially in excess of said triggering current prior to the initiation of operation in its high-resistance mode so as to abruptly energize said switch device for a predetermined time interval, high-resistance operation of said first PTC thermistor being positively initiated upon expiration of said predetermined time interval effecting a reduction in the flow of current therethrough rendering said switch device nonconductive, said first PTC thermistor being coupled to the run winding to receive sufficient current during running of the motor subsequent to the predetermined time interval to maintain said first PTC thermistor in its high-resistance mode, and current-limiting means connected between said first thermistor and said switch device for limiting the current applied to said control terminal to a level sufficient to maintain said switch device conductive only until high-resistance operation of said first PTC thermistor is effected, said current-limiting means being effective to limit triggering current supplied to said control terminal when the current flow through said first PTC thermistor is reduced due to high-resistance operation thereof to effect abrupt energization of said switch device, and means for energizing the start winding and said trigger means so as to apply triggering current through said first PTC thermistor to energize said switch device, whereby current flow is effected through the start winding during said Predetermined time interval.

Claim 15

A system for controlling the operation of an induction motor having a start winding and a run winding comprising a first selectively energizable semiconductor switch device having a pair of power terminals and a control terminal for controlling the flow of current between said power terminals in response to a triggering current, said power terminals being connected between the start winding and a source of power, trigger means, including a first PTC thermistor adapted for operation in a high-resistance mode coupled to said control terminal for controlling the application of triggering current thereto, said first PTC thermistor being adapted to conduct current substantially in excess of said triggering current prior to the initiation of operation in its high-resistance mode so as to abruptly energize said switch device for a predetermined time interval, high-resistance operation of said first PTC thermistor being positively initiated upon expiration of said predetermined time interval effecting a reduction in the flow of current therethrough rendering said switch device nonconductive, said first PTC thermistor being coupled to the run winding to receive sufficient current during running of the motor subsequent to said predetermined time interval to maintain said first PTC thermistor operational in its high-resistance mode, and current-limiting means including at least two electrically connected resistors coupled between said first PTC thermistor and said control terminal and between said first PTC thermistor and one of said power terminals of said switch device respectively for limiting the current applied to said control terminal to a level sufficient to maintain said switch device conductive only until high-resistance operation of said first PTC thermistor is effected, said current-limiting means being effective to limit triggering current supplied to said control terminal when the current flow through said first PTC thermistor is reduced due to high-resistance operation thereof to effect abrupt deenergization of said switch device, and means for energizing the start winding and said trigger means so as to apply triggering current through said first PTC thermistor to energize said switch device, whereby current flow is effected through the start winding during said predetermined time interval.

Claim 16

A system for controlling the operation of an induction motor having a start winding and a run winding comprising a first selectively energizable semiconductor switch device having a pair of power terminals and a control terminal for controlling the flow of current between said power terminals in response to a triggering current, said power terminals being connected between the start winding and a source of power, trigger means, including a first PTC thermistor adapted for operation in a high-resistance mode coupled to said control terminal for controlling the application of triggering current thereto, said first PTC thermistor being adapted to conduct current substantially in excess of said triggering current prior to the initiation of operation in its high-resistance mode so as to abruptly energize said switch device for a predetermined time interval, high-resistance operation of said first PTC thermistor being positively initiated upon expiration of said predetermined time interval effecting a reduction in the flow of current therethrough rendering said switch device nonconductive, said first PTC thermistor being coupled to the run winding to receive sufficient current during running of the motor subsequent to said predetermined time interval to maintain said first PTC thermistor operational in its high-resistance mode, and current-limiting means including at least two electrically connected resistors coupled between said first PTC thermistor and said control terminal and between said first PTC thermistor and one of said power terminals of said switch device respectively for limiting the current applied to said control terminal to a level sufficient to maintain said switch device conductive only until high-resistance operation of said first PTC thermistor is effected, said current-limiting means being effective to limit triggering current supplied to said control terminal when the current flow through said first PTC thermistor is reduced due to high-resistance operation thereof to effect abrupt deenergization of said switch device, and means for energizing the start winding and said trigger means so as to apply triggering current through said first PTC thermistor to energize said switch device, whereby current flow is effected through the start winding during said predetermined time interval.

Claim 24

A system for controlling the operation of an induction motor having a start winding and a run winding comprising a selectively energizable semiconductor current switch device having a pair of power terminals and a control terminal for controlling the flow of current between said power terminals in response to a triggering current, said power terminals being serially connected between the start winding and a source of power, trigger means including a first PTC thermistor adapted for operation in a high-resistance mode at a first predetermined temperature coupled to said control terminal for controlling the application of triggering current thereto, said first PTC thermistor being adapted to conduct triggering current to said control terminal for a time interval required to permit sufficient heating of said first PTC thermistor to effect operation in its high-resistance mode reducing the triggering current flow therethrough so as to render said switch device nonconductive, and a second PTC thermistor adapted for operation in a high-resistance mode at a second predetermined temperature in excess of said first predetermined temperature connected across the start winding and electrically connected to said first PTC thermistor, said second PTC thermistor being in thermal communication with said first PTC thermistor, so as to apply heat thereto during said time interval, to assure a positive transition into high-resistance operation of said first PTC thermistor, thereby effecting abrupt deenergization of said switch device upon the expiration of said time interval, means for energizing the start winding and said trigger means so as to effect the application of triggering cuRrent through said first and second PTC thermistors to said control terminal only until expiration of said time interval, and means for maintaining said second PTC thermistor in its high-resistance mode subsequent to said time interval and during the application of power to the run winding so as to prevent the application of triggering current to said switch device and for effecting reapplication of triggering current to said switch device upon cooling of said first and second PTC thermistors permitting triggering current to flow therethrough.

Claim 25

A system for controlling the operation of an induction motor having a start winding and a run winding comprising a selectively energizable semiconductor current switch device having a pair of power terminals and a control terminal for controlling the flow of current between said power terminals in response to a triggering current, said power terminals being serially connected between the start winding and a source of power, trigger means including a first PTC thermistor adapted for operation in a high-resistance mode at a first predetermined temperature coupled to said control terminal for controlling the application of triggering current thereto, said first PTC thermistor being adapted to conduct triggering current to said control terminal for a time interval required to permit sufficient heating of said first PTC thermistor to effect operation in its high-resistance mode reducing the triggering current flow therethrough so as to render said switch device nonconductive, and a second PTC thermistor adapted for operation in a high-resistance mode at a second predetermined temperature in excess of said first predetermined temperature connected across the start winding and electrically connected to said first PTC thermistor, said second PTC thermistor being in thermal communication with said first PTC thermistor, so as to apply heat thereto during said time interval, to assure a positive transition into high-resistance operation of said first PTC thermistor, thereby effecting abrupt deenergization of said switch device upon the expiration of said time interval, means for energizing the start winding and said trigger means so as to effect the application of triggering cuRrent through said first and second PTC thermistors to said control terminal only until expiration of said time interval, and means for maintaining said second PTC thermistor in its high-resistance mode subsequent to said time interval and during the application of power to the run winding so as to prevent the application of triggering current to said switch device and for effecting reapplication of triggering current to said switch device upon cooling of said first and second PTC thermistors permitting triggering current to flow therethrough.

Claim 28

A system for controlling the operation of an induction motor having a start winding and a run winding comprising a selectively energizable semiconductor current switch device having a pair of power terminals and a control terminal for controlling the flow of current between said power terminals in response to a triggering current, said power terminals being serially connected between the start winding and a source of power, trigger means including a first PTC thermistor adapted for operation in a high-resistance mode at a first predetermined temperature coupled to said control element, said first PTC thermistor being adapted to conduct triggering current to said control element for a preselected time interval until the increase in resistance thereof is sufficient to effect a reduction in triggering current flow to render said switch device nonconductive, and a second PTC thermistor adapted for operation in a high-resistance mode at a second predetermined temperature in excess of said first predetermined temperature, said second PTC thermistor being connected across the run winding and in thermal communication with said first PTC thermistor so as to apply heat to said first PTC thermistor during said predetermined time interval to assure a positive transition into high-resistance operation thereof, permitting abrupt deenergization of said switch device upon expiration of said predetermined time interval, means for energizing the start winding and said trigger means to supply triggering current to said control terminal through said first PTC thermistor for said predetermined time interval and for supplying current to said second PTC thermistor to effect heating thereof, and means for maintaining said second PTC thermistor in an energized condition to effect the application of sufficient heat to said first PTC thermistor to maintain said first PTC thermistor operational in a high-resistance mode during running of the motor subsequent to said predetermined time interval.

Claim 29

A system for controlling the operation of an induction motor having a start winding and a run winding comprising a selectively energizable semiconductor current switch device having a pair of power terminals and a control terminal for controlling the flow of current between said power terminals in response to a triggering current, said power terminals being serially connected between the start winding and a source of power, trigger means including a first PTC thermistor adapted for operation in a high-resistance mode at a first predetermined temperature coupled to said control element, said first PTC thermistor being adapted to conduct triggering current to said control element for a preselected time interval until the increase in resistance thereof is sufficient to effect a reduction in triggering current flow to render said switch device nonconductive, and a second PTC thermistor adapted for operation in a high-resistance mode at a second predetermined temperature in excess of said first predetermined temperature, said second PTC thermistor being connected across the run winding and in thermal communication with said first PTC thermistor so as to apply heat to said first PTC thermistor during said predetermined time interval to assure a positive transition into high-resistance operation thereof, permitting abrupt deenergization of said switch device upon expiration of said predetermined time interval, means for energizing the start winding and said trigger means to supply triggering current to said control terminal through said first PTC thermistor for said predetermined time interval and for supplying current to said second PTC thermistor to effect heating thereof, and means for maintaining said second PTC thermistor in an energized condition to effect the application of sufficient heat to said first PTC thermistor to maintain said first PTC thermistor operational in a high-resistance mode during running of the motor subsequent to said predetermined time interval.