Motor starting circuit

Claim 2

A motor starting circuit for momentarily energizing the starting winding circuit of a single-phase, alternating current motor, comprising: a triac connected, via the main terminals thereof, in series with said starting winding circuit; and a switching circuit having first and second input terminals and a gate terminal, wherein the switching circuit is connected, via the input terminals thereof, in parallel with the serially connected triac and starting winding circuit, the second input terminal of the switching circuit being connected to a main terminal of the triac with the opposite main terminal thereof connected to the starting winding circuit, wherein the gate terminal of the switching circuit is connected to the gate of the triac, and wherein the switching circuit comprises: a biasing resistor connected between the gate terminal and the second input terminal of the switching circuit, and timing means, connected between the first input terminal of the switching circuit and the gate terminal thereof for establishing a relatively low effective resistance between the first input terminal and the triac gate for a preselected time period following connection of the motor to an electrical source and thereafter establishing a relatively high effective resistance between the first input terminal and the triac gate, said timing means including: a load resistor having one end thereof connected to the first input terminal of the switching circuit; a full-wave recifier bridge having the input terminals thereof connected between the other end of the load resistor and the gate terminal of the switching circuit; a first SCR connected in parallel across the output terminals of the rectifier bridge so as to substantially provide a short circuit between the load resistor and the gate terminal of the switching circuit at such time that the first SCR is in a conducting state; a first SCR gating branch, comprising: a first gating branch resistor connected between the cathode and gate of said first SCR; a second gating branch resistor having one end thereof connected to the junction of the first gating branch resistor and a gate of said first SCR; and a third gating branch resistor connected between the other end of the second gating branch resistor and the anode of said first SCR, wherein the third gating branch resistor has a resistance which is large in relation to the resistance of the load resistor; a timing branch, comprising: a timing resistor having one end thereof connected to the anode of said first SCR; and a timing capacitor connected between the other end of the timing resistor and the cathode of said SCR for charging through the timing resistor; and turn-off means, connected between the junction of the timing resistor and timing capacitor, the junction of the second and third gating branch resistors, and the junction of the first gating branch resistor and the first SCR cathode, for substantially providing a short circuit across the first and second gating branch resistors in response to charging of the timing capacitor to a preselected level.

Claim 3

The motor starting circuit of claim 1 wherein the first SCR turn-off means is a second SCR having the anode thereof connected to the junction of the second and third gating branch resistors, having the cathode thereof connected to the junction of the first SCR cathode and the first gating branch resistor and having the gate thereof connected to the junction of the timing resistor and timing capacitor.

Claim 4

A motor starting circuit for momentarily energizing the starting winding circuit of a single-phase, alternating current motor, comprising: a triac connected, via the main terminals thereof, in series with said starting winding circuit; and a switching circuit having first and second input terminals and a gate terminal, wherein the switching circuit is connected, via the input terminals thereof, in parallel with the serially connected triac and starting winding circuit, the second input terminal of the switching circuit being connected to a main terminal of the triac with the opposite main terminal thereof connected to the starting winding circuit, wherein the gate terminal of the switching circuit is connected to the gate of the triac, and wherein the switching circuit comprises: a biasing resistor connected between the gate terminal and the second input terminal of the switching circuit, and timing means, connected between the first input terminal of the switching circuit and the gate terminal thereof for establishing a relatively low effective resistance between the first input terminal and the triac gate for a preselected time period following connection of the motor to an electrical source and thereafter establishing a relatively high effective resistance between the first input terminal and the triac gate, said timing means including: a full-wave rectifier bridge having the input terminals thereof connected between the first input terminal of the switching circuit and the gate terminal of the switching circuits; a load resistor having one end thereof connected to one output terminal of the rectifier bridge; a first SCR connected between the load resistor and the other output terminal of the rectifier bridge so as to substantially provide a short circuit between the load resistor and said other output terminal of the rectifier bridge at such time that the first SCR is gated into a conducting state; a first SCR gating branch comprising: a first gating branch resistor connected between the cathode and gate of said first SCR; a second gating branch resistor having one end thereof connected to the junction of the first gating branch resistor and the gate of said first SCR; and a third gating branch resistor connected between the other end of the second gating branch resistor and the end of the load resistor connected to the rectifier bridge, wherein the third gating branch resistor has a resistance which is large in relation to the resistance of the load resistor; a timing branch, comprising: a timing resistor having one end thereof connected to the end of the load resistor connected to the rectifier bridge; and a timing capacitor connected between the other end of the timing resistor and the cathode of said first SCR for charging through the timing resistors; and turn-off means, connected between the junction of the timing resistor and timing capacitor, the junction of the second and third gating branch resistors, and the junction of the first gating branch resistor and the first SCR cathode, for substantially providing a short circuit across the first and second gating branch resistors in response to charging of the timing capacitor to a preselected level.

Claim 5

A motor starting circuit for momentarily energizing the starting winding circuit of a single-phase, alternating current motor, comprising: a triac connected, via the main terminals thereof, in series with said starting winding circuit; and a switching circuit having first and second input terminals and a gate terminal, wherein the switching circuit is connected, via the input terminals thereof, in parallel with the serially connected triac and starting winding circuit, the second input terminal of the switching circuit being connected to a main terminal of the triac with the opposite main terminal thereof connected to the starting winding circuit, wherein the gate terminal of the switching circuit is connected to the gate of the triac, and wherein the switching circuit comprises: a biasing resistor connected between the gate terminal and the second input terminal of the switching circuit, and timing means, connected between the first input terminal of the switching circuit and the gate terminal thereof for establishing a relatively low effective resistance between the first input terminal and the triac gate for a preselected time period following connection of the motor to an electrical source and thereafter establishing a relatively high effective resistance between the first input terminal and the triac gate, said timing means including: a full-wave rectifier bridge having the input terminals thereof connected between the first input terminal of the switching circuit and the gate terminal of the switching circuits; a load resistor having one end thereof connected to one output terminal of the rectifier bridge; a first SCR connected between the load resistor and the other output terminal of the rectifier bridge so as to substantially provide a short circuit between the load resistor and said other output terminal of the rectifier bridge at such time that the first SCR is gated into a conducting state; a first SCR gating branch comprising: a first gating branch resistor connected between the cathode and gate of said first SCR; a second gating branch resistor having one end thereof connected to the junction of the first gating branch resistor and the gate of said first SCR; and a third gating branch resistor connected between the other end of the second gating branch resistor and the end of the load resistor connected to the rectifier bridge, wherein the third gating branch resistor has a resistance which is large in relation to the resistance of the load resistor; a timing branch, comprising: a timing resistor having one end thereof connected to the end of the load resistor connected to the rectifier bridge; and a timing capacitor connected between the other end of the timing resistor and the cathode of said first SCR for charging through the timing resistors; and turn-off means, connected between the junction of the timing resistor and timing capacitor, the junction of the second and third gating branch resistors, and the junction of the first gating branch resistor and the first SCR cathode, for substantially providing a short circuit across the first and second gating branch resistors in response to charging of the timing capacitor to a preselected level.

Claim 6

The motor starting circuit of claim 3 wherein the turn-off means is a second SCR having the anode thereof connected to the junction of the second and third gating branch resistors, having the cathode thereof connected to the junction of the first SCR cathode and the first gating branch resistor and having the gate thereof connected to the junction of the timing resistor and timing capacitor.

Claim 7

A motor starting circuit for momentarily energizing the starting winding circuit of a single-phase, alternating current motor, comprising: a triac connected, via the main terminals thereof, in series with said starting winding circuit; and a switching circuit having first and second input terminals and a gate terminal, wherein the switching circuit is connected, via the input terminals thereof, in parallel with the serially connected triac and starting winding circuit, the second input terminal of the switching circuit being connected to a main terminal of the triac with the opposite main terminal thereof connected to the starting winding circuit, wherein the gate terminal of the switching circuit is connected to the gate of the triac, and wherein the switching circuit comprises: a biasing resistor connected between the gate terminal and the second input terminal of the switching circuit; and timing means, connected between the first input terminal of the switching circuit and the gate terminal thereof for establishing a relatively low effective resistance between the first input terminal and the triac gate for a preselected time period following connection of the motor to an electrical source and thereafter establishing a relatively high effective resistance between the first input terminal and the triac gate, said timing means including: a voltage limiter having one electrode thereof connected to the first input terminal of the switching circuit; a full-wave rectifier bridge having the input terminals thereof connected between the other electrode of the glow discharge tube and the gate terminal of the switching circuit; a load resistor having one end thereof connected to an output terminal of the rectifier bridge; a first SCR connected between the load resistor and the other ouput terminal of the rectifier bridge so as to substantially provide a short circuit between the load resistor and said other output terminal of the rectifier bridge at such times that the first SCR is gated into a conducted state; a first SCR gating branch, comprising: a first gating branch resistor connected between the cathode and gate of said first SCR; a second gating branch resistor having one end thereof connected to the junction of the first gating branch resistor and the gate of said first SCR; and a third gating branch resistor connected between the other end of the second gating branch resistor and the end of the load resistor connected to the rectifier bridge, wherein the third gating branch resistor has a resistance which is large in relation to the resistance of the load resistor; a timing branch, comprising: a timing resistor having one end thereof connected to the end of the load resistor connected to the rectifier bridge; and a timing capacitor connected between the other end of the timing resistor and the cathode of said first SCR for charging through the timing resistor; and turn-off means, connected between the junction of the timing resistor and timing capacitor, the junction of the second and third gating branch resistors, and the junction of the first gating branch resistor and the first SCR cathode, for substantially providing a short circuit across the first and second gating branch resistors in response to charging of the timing capacitor to a preselected level.

Claim 8

A motor starting circuit for momentarily energizing the starting winding circuit of a single-phase, alternating current motor, comprising: a triac connected, via the main terminals thereof, in series with said starting winding circuit; and a switching circuit having first and second input terminals and a gate terminal, wherein the switching circuit is connected, via the input terminals thereof, in parallel with the serially connected triac and starting winding circuit, the second input terminal of the switching circuit being connected to a main terminal of the triac with the opposite main terminal thereof connected to the starting winding circuit, wherein the gate terminal of the switching circuit is connected to the gate of the triac, and wherein the switching circuit comprises: a biasing resistor connected between the gate terminal and the second input terminal of the switching circuit; and timing means, connected between the first input terminal of the switching circuit and the gate terminal thereof for establishing a relatively low effective resistance between the first input terminal and the triac gate for a preselected time period following connection of the motor to an electrical source and thereafter establishing a relatively high effective resistance between the first input terminal and the triac gate, said timing means including: a voltage limiter having one electrode thereof connected to the first input terminal of the switching circuit; a full-wave rectifier bridge having the input terminals thereof connected between the other electrode of the glow discharge tube and the gate terminal of the switching circuit; a load resistor having one end thereof connected to an output terminal of the rectifier bridge; a first SCR connected between the load resistor and the other ouput terminal of the rectifier bridge so as to substantially provide a short circuit between the load resistor and said other output terminal of the rectifier bridge at such times that the first SCR is gated into a conducted state; a first SCR gating branch, comprising: a first gating branch resistor connected between the cathode and gate of said first SCR; a second gating branch resistor having one end thereof connected to the junction of the first gating branch resistor and the gate of said first SCR; and a third gating branch resistor connected between the other end of the second gating branch resistor and the end of the load resistor connected to the rectifier bridge, wherein the third gating branch resistor has a resistance which is large in relation to the resistance of the load resistor; a timing branch, comprising: a timing resistor having one end thereof connected to the end of the load resistor connected to the rectifier bridge; and a timing capacitor connected between the other end of the timing resistor and the cathode of said first SCR for charging through the timing resistor; and turn-off means, connected between the junction of the timing resistor and timing capacitor, the junction of the second and third gating branch resistors, and the junction of the first gating branch resistor and the first SCR cathode, for substantially providing a short circuit across the first and second gating branch resistors in response to charging of the timing capacitor to a preselected level.

Claim 9

The motor starting circuit of claim 5 wherein the turn-off means is a second SCR having the anode thereof connected to the junction of the second and third gating branch resistors, having the cathode thereof connected to the junction of the first SCR cathode and the first gating branch resistor and having the gate thereof connected to the junction of the timing resistor and timing capacitor.

Claim 10

The motor starting circuit of claims 1, 3, or 5 wherein the turn-off means is: a second SCR having the anode thereof connected to the junction of the second and third gating branch resistors and having the cathode thereof connected to the junction of the first SCR cathode and the first gating branch resistor; a zener diode having the anode thereof connected to the gate of said second SCR and the cathode thereof connected to the junction of the timing resistor and timing capacitor.

Claim 11

The motor starting circuit of claims 1, 3, or 5 wherein the turn-off means is: a second SCR having the anode thereof connected to the cathodes of a pair of diodes, the cathode of second SCR being connected to the junction of the first SCR cathode and the first gating branch resistor and having the gate thereof connected to the junction of the timing resistor and timing capacitor, one of said pair of diodes having its anode connected to the junction of the second and third gating branch resistors and the other of said pair of diodes having its anode connected to the junction of the timing resistor and timing capacitor.

Claim 12

The motor starting circuit of claims 1, 3, or 5 wherein the turn-off means is: a second SCR having the cathode thereof connected to the junction of the first SCR cathode and the first gating branch resistor; a zener diode having its anode connected to the gate of said second SCR and its cathode connected to the gate of said second SCR and its cathode connected to the junction of the timing resistor and timing capacitor, the anode of said second SCR connected to the cathodes of a pair of diodes, the anode of one of said pair of diodes connected to the junction of the second and third gating branch resistors, the other said pair of diodes having its anode connected to the junction of the timing resistor and timing capacitor.

Claim 13

A motor starting circuit for momentarily energizing the starting winding circuit of a single-phase, alternating current motor, comprising: a triac connected, via the main terminals thereof, in series with said starting winding circuit; and a switching circuit having first and second input terminals and a gate terminal, wherein the switching circuit is connected, via the input terminals thereof, in parallel with the serially connected triac and starting winding circuit, the second input terminal of the switching circuit being connected to a main terminal of the triac with the opposite main terminal thereof connected to the starting winding circuit, wherein the gate terminal of the switching circuit is connected to the gate of the triac, and wherein the switching circuit comprises: a biasing resistor connected between the gate terminal and the second input terminal of the switching circuit, and timing means, connected between the first input terminal of the switching circuit and the gate terminal thereof for establishing a relatively low effective resistance between the first input terminal and the triac gate for a preselected time period following connection of the motor to an electrical source and thereafter establishing a relatively high effective resistance between the first input terminal and the triac gate, said timing means including: a load resistor having one end thereof connected to the first input terminal of the switching circuit; a full-wave rectifer bridge having the input terminals thereof connected between the other end of the load resistor and the gate terminal of the switching circuit; a first SCR connected in parallel across the output terminals of the rectifier bridge so as to substantially provide a short circuit between the load resistor and the gate terminal of the switching circuit at such time that the first SCR is in a conducting state; a first SCR gating branch, comprising: a first gating branch resistor connected between the cathode and gate of said first SCR; a zener diode having its anode connected to the junction of the first gating branch resistor and a gate of said first SCR; and a second gating branch resistor connected between the cathode of said zener diode and the anode of said first SCR, wherein the second gating branch resistor has a resistance which is large in relation to the resistance of the load resistor; a timing branch, comprising: a timing resistor having one end thereof connected to the anode of said first SCR; and a timing capacitor connected between the other end of the timing resistor and the cathode of said SCR for charging through the timing resistor; and turn-off means, connected between the junction of the timing resistor and timing capacitor, the junction of said zener diode and second gating branch resistor, and the junction of the first gating branch resistor and the first SCR cathode, for substantially providing a short circuit across the first gating branch resistor and said zener diode in response to charging of the timing capacitor to a preselected level.

Claim 14

A motor starting circuit for momentarily energizing the starting winding circuit of a single-phase, alternating current motor, comprising: a triac connected, via the main terminals thereof, in series with said starting winding circuit; and a switching circuit having first and second input terminals and a gate terminal, wherein the switching circuit is connected, via the input terminals thereof, in parallel with the serially connected triac and starting winding circuit, the second input terminal of the switching circuit being connected to a main terminal of the triac with the opposite main terminal thereof connected to the starting winding circuit, wherein the gate terminal of the switching circuit is connected to the gate of the triac, and wherein the switching circuit comprises: a biasing resistor connected between the gate terminal and the second input terminal of the switching circuit, and timing means, connected between the first input terminal of the switching circuit and the gate terminal thereof for establishing a relatively low effective resistance between the first input terminal and the triac gate for a preselected time period following connection of the motor to an electrical source and thereafter establishing a relatively high effective resistance between the first input terminal and the triac gate, said timing means including: a load resistor having one end thereof connected to the first input terminal of the switching circuit; a full-wave rectifer bridge having the input terminals thereof connected between the other end of the load resistor and the gate terminal of the switching circuit; a first SCR connected in parallel across the output terminals of the rectifier bridge so as to substantially provide a short circuit between the load resistor and the gate terminal of the switching circuit at such time that the first SCR is in a conducting state; a first SCR gating branch, comprising: a first gating branch resistor connected between the cathode and gate of said first SCR; a zener diode having its anode connected to the junction of the first gating branch resistor and a gate of said first SCR; and a second gating branch resistor connected between the cathode of said zener diode and the anode of said first SCR, wherein the second gating branch resistor has a resistance which is large in relation to the resistance of the load resistor; a timing branch, comprising: a timing resistor having one end thereof connected to the anode of said first SCR; and a timing capacitor connected between the other end of the timing resistor and the cathode of said SCR for charging through the timing resistor; and turn-off means, connected between the junction of the timing resistor and timing capacitor, the junction of said zener diode and second gating branch resistor, and the junction of the first gating branch resistor and the first SCR cathode, for substantially providing a short circuit across the first gating branch resistor and said zener diode in response to charging of the timing capacitor to a preselected level.

Claim 15

A motor starting circuit for momentarily energizing the starting winding circuit of a single-phase, alternating current motor, comprising: a triac connected, via the main terminals thereof, in series with said starting winding circuit; and a switching circuit having first and second input terminals and a gate terminal, wherein the switching circuit is connected, via the input terminals thereof, in parallel with the serially connected triac and starting winding circuit, the second input terminal of the switching circuit being connected to a main terminal of the triac with the opposite main terminal thereof connected to the starting winding circuit, wherein the gate terminal of the switching circuit is connected to the gate of the triac, and wherein the switching circuit comprises: a biasing resistor connected between the gate terminal and the second input terminal of the switching circuit, and timing means, connected between the first input terminal of the switching circuit and the gate terminal thereof for establishing a relatively low effective resistance between the first input terminal and the triac gate for a preselected time period following connection of the motor to an electrical source and thereafter establishing a relatively high effective resistance between the first input terminal and the triac gate, said timing means including: a full-wave rectifier bridge having the input terminals thereof connected between the first input terminal of the switching circuit and the gate terminal of the switching circuits; a load resistor having one end thereof connected to one output terminal of the rectifier bridge; a first SCR connected between the load resistor and the other output terminal of the rectifier bridge so as to substantially provide a short circuit between the load resistor and said other output terminal of the rectifier bridge at such time that the first SCR is gated into a conducting state; a first SCR gating branch comprising: a first gating branch resistor connected between the cathode and gate of said first SCR; a zener diode having its anode connected to the junction of the first gating branch resistor and the gate of said first SCR; and a second gating branch resistor connected between the cathode of said zener diode and the end of the load resistor connected to the rectifier bridge, wherein the second gating branch resistor has a resistance which is large in relation to the resistance of the load resistor; a timing branch, comprising: a timing resistor having one end thereof connected to the end of the load resistor connected to the rectifier bridge; and a timing capacitor connected between the other end of the timing resistor and the cathode of said first SCR for charging through the timing resistors; and turn-off means, connected between the junction of the timing resistor and timing capacitor, the junction of said zener diode and second gating branch resistor, and the junction of the first gating branch resistor and the first SCR cathode, for substantially providing a short circuit across the first gating branch resistor and said zener diode in response to charging of the timing capacitor to a preselected level.

Claim 16

A motor starting circuit for momentarily energizing the starting winding circuit of a single-phase, alternating current motor, comprising: a triac connected, via the main terminals thereof, in series with said starting winding circuit; and a switching circuit having first and second input terminals and a gate terminal, wherein the switching circuit is connected, via the input terminals thereof, in parallel with the serially connected triac and starting winding circuit, the second input terminal of the switching circuit being connected to a main terminal of the triac with the opposite main terminal thereof connected to the starting winding circuit, wherein the gate terminal of the switching circuit is connected to the gate of the triac, and wherein the switching circuit comprises: a biasing resistor connected between the gate terminal and the second input terminal of the switching circuit, and timing means, connected between the first input terminal of the switching circuit and the gate terminal thereof for establishing a relatively low effective resistance between the first input terminal and the triac gate for a preselected time period following connection of the motor to an electrical source and thereafter establishing a relatively high effective resistance between the first input terminal and the triac gate, said timing means including: a full-wave rectifier bridge having the input terminals thereof connected between the first input terminal of the switching circuit and the gate terminal of the switching circuits; a load resistor having one end thereof connected to one output terminal of the rectifier bridge; a first SCR connected between the load resistor and the other output terminal of the rectifier bridge so as to substantially provide a short circuit between the load resistor and said other output terminal of the rectifier bridge at such time that the first SCR is gated into a conducting state; a first SCR gating branch comprising: a first gating branch resistor connected between the cathode and gate of said first SCR; a zener diode having its anode connected to the junction of the first gating branch resistor and the gate of said first SCR; and a second gating branch resistor connected between the cathode of said zener diode and the end of the load resistor connected to the rectifier bridge, wherein the second gating branch resistor has a resistance which is large in relation to the resistance of the load resistor; a timing branch, comprising: a timing resistor having one end thereof connected to the end of the load resistor connected to the rectifier bridge; and a timing capacitor connected between the other end of the timing resistor and the cathode of said first SCR for charging through the timing resistors; and turn-off means, connected between the junction of the timing resistor and timing capacitor, the junction of said zener diode and second gating branch resistor, and the junction of the first gating branch resistor and the first SCR cathode, for substantially providing a short circuit across the first gating branch resistor and said zener diode in response to charging of the timing capacitor to a preselected level.

Claim 17

A motor starting circuit for momentarily energizing the starting winding circuit of a single-phase, alternating current motor, comprising: a triac connected, via the main terminals thereof, in series with said starting winding circuit; and a switching circuit having first and second input terminals and a gate terminal, wherein the switching circuit is connected, via the input terminals thereof, in parallel with the serially connected triac and starting winding circuit, the second input terminal of the switching circuit being connected to a main terminal of the triac with the opposite main terminal thereof connected to the starting winding circuit, wherein the gate terminal of the switching circuit is connected to the gate of the triac, and wherein the switching circuit comprises: a biasing resistor connected between the gate terminal and the second input terminal of the switching circuit, and timing means, connected between the first input terminal of the switching circuit and the gate terminal thereof for establishing a relatively low effective resistance between the first input terminal and the triac gate for a preselected time period following connection of the motor to an electrical source and thereafter establishing a relatively high effective resistance between the first input terminal and the triac gate, said timing means including: a voltage limiter having one electrode thereof connected to the first input terminal of the switching circuit; a full-wave rectifier bridge having the input terminals thereof connected between the other electrode of the glow discharge tube and the gate terminal of the switching circuit; a load resistor having one end thereof connected to an output terminal of the rectifier bridge; a first SCR connected between the load resistor and the other output terminal of the rectifier bridge so as to substantially provide a short circuit between the load resistor and said other output terminal of the rectifier bridge at such times that the first SCR is gated into a conducted state; a first SCR gating branch, comprising: a first gating branch resistor connected between the cathode and gate of said first SCR; a zener diode having its anode connected to the junction of the first gating branch resistor and the gate of said first SCR; and a second gating branch resistor connected between the cathode of said zener diode and the end of the load resistor connected to the rectifier bridge, wherein the second gating branch resistor has a resistance which is large in relation to the resistance of the load resistor; a timing branch, comprising: a timing resistor having one end thereof connected to the end of the load resistor connected to the rectifier bridge; and a timing capacitor connected between the other end of the timing resistor and the cathode of said first SCR for charging through the timing resistor; and turn-off means, connected between the junction of the timing resistor and timing capacitor, the junction of said zener diode and second gating branch resistor, and the junction of the first gating branch resistor and the first SCR cathode, for substantially providing a short circuit across the first gating branch resistor and said zener diode in response to charging of the timing capacitor to a preselected level.

Claim 18

A motor starting circuit for momentarily energizing the starting winding circuit of a single-phase, alternating current motor, comprising: a triac connected, via the main terminals thereof, in series with said starting winding circuit; and a switching circuit having first and second input terminals and a gate terminal, wherein the switching circuit is connected, via the input terminals thereof, in parallel with the serially connected triac and starting winding circuit, the second input terminal of the switching circuit being connected to a main terminal of the triac with the opposite main terminal thereof connected to the starting winding circuit, wherein the gate terminal of the switching circuit is connected to the gate of the triac, and wherein the switching circuit comprises: a biasing resistor connected between the gate terminal and the second input terminal of the switching circuit, and timing means, connected between the first input terminal of the switching circuit and the gate terminal thereof for establishing a relatively low effective resistance between the first input terminal and the triac gate for a preselected time period following connection of the motor to an electrical source and thereafter establishing a relatively high effective resistance between the first input terminal and the triac gate, said timing means including: a voltage limiter having one electrode thereof connected to the first input terminal of the switching circuit; a full-wave rectifier bridge having the input terminals thereof connected between the other electrode of the glow discharge tube and the gate terminal of the switching circuit; a load resistor having one end thereof connected to an output terminal of the rectifier bridge; a first SCR connected between the load resistor and the other output terminal of the rectifier bridge so as to substantially provide a short circuit between the load resistor and said other output terminal of the rectifier bridge at such times that the first SCR is gated into a conducted state; a first SCR gating branch, comprising: a first gating branch resistor connected between the cathode and gate of said first SCR; a zener diode having its anode connected to the junction of the first gating branch resistor and the gate of said first SCR; and a second gating branch resistor connected between the cathode of said zener diode and the end of the load resistor connected to the rectifier bridge, wherein the second gating branch resistor has a resistance which is large in relation to the resistance of the load resistor; a timing branch, comprising: a timing resistor having one end thereof connected to the end of the load resistor connected to the rectifier bridge; and a timing capacitor connected between the other end of the timing resistor and the cathode of said first SCR for charging through the timing resistor; and turn-off means, connected between the junction of the timing resistor and timing capacitor, the junction of said zener diode and second gating branch resistor, and the junction of the first gating branch resistor and the first SCR cathode, for substantially providing a short circuit across the first gating branch resistor and said zener diode in response to charging of the timing capacitor to a preselected level.

Claim 19

The motor starting circuit of claims 10, 11, or 12 wherein the turn-off means is: a second SCR having the anode thereof connected to the junction of said first mentioned zener diode and second gating branch resistor and having the cathode thereof connected to the junction of the first SCR cathode and the first gating branch resistor, a second zener diode having the anode thereof connected to the gate of said second SCR and the cathode thereof connected to the junction of the timing resistor and timing capacitor.

Claim 20

The motor starting circuit of claims 10, 11, or 12 wherein the turn-off means is: a second SCR having the anode thereof connected to the cathodes of a pair of diodes, the cathode of second SCR being connected to the junction of the first SCR cathode and the first gating branch resistor and having the gate thereof connected to the junction of the timing resistor and timing capacitor, one of said pair of diodes having its anode connected to the junction of said zener diode and second gating branch resistor and the other of said pair of diodes having its anode connected to the junction of the timing resistor and timing capacitor.

Claim 21

The motor starting circuit of claims 10, 11, or 12 wherein the turn-off means is: a second SCR having the cathode thereof connected to the junction of the first SCR cathode and the first gating branch resistor, a second zener diode having its anode connected to the gate of said second SCR and its cathode connected to the junction of the timing resistor and timing capacitor, the anode of said second SCR connected to the cathodes of a pair of diodes, the anode of one of said pair of diodes connected to the junction of said first mentioned zener diode and second gating branch resistor, the other of said pair of diodes having its anode connected to the junction of the timing resistor and timing capacitor.