Motor starting circuit with low cost comparator hysteresis
First Claim
1. In a single phase AC induction motor having a main winding and an auxiliary winding both connectable to an AC power source, and having a switch for disconnecting said auxiliary winding from said AC source, a control circuit for said switch comprising:
- main voltage detector means sensing voltage from said AC source;
auxiliary voltage detector means sensing auxiliary winding voltage;
voltage comparator means having a first input connected to said main voltage detector means and a second input connected to said auxiliary voltage detector means and comparing said auxiliary winding voltage against said voltage from said AC source and outputting a turn-off signal causing said switch to disconnect said auxiliary winding from said AC source when said auxiliary winding voltage increases to a predetermined cut-out value relative to said voltage from said AC source as a function of motor speed, and outputting a turn-on signal causing said switch to connect said auxiliary winding to said AC source when said auxiliary winding voltage decreases to a predetermined cut-in value relative to said voltage from said AC source as a function of motor speed, said predetermined cut-in value corresponding to a voltage derived from rotationally induced voltage in said auxiliary winding during overload or stall of said motor after starting;
hysteresis means responsive to said turn-off signal to change the voltage at one of said inputs of said comparator means such that said auxiliary winding voltage must decrease to a cut-in value which is less than said cut-out value before reconnection of said auxiliary winding to said AC source, wherein said hysteresis means comprises a connection between the output of said comparator means and said one input of said comparator means to adjust the voltage level at said one input according to said output.
7 Assignments
0 Petitions
Accused Products
Abstract
A low cost, low part content single phase AC induction motor control starting circuit is provided which is speed sensitive, load sensitive and AC line voltage fluctuation insensitive. A dual comparator chip (20, 22) senses and compares relative magnitudes of AC line and auxiliary winding voltages (48, 40) to de-energize the auxiliary winding (2) at cut-out speed, and automatically re-energize the auxiliary winding at cut-in speed to accelerate or restart the motor from an overload or stall condition. Hysteresis circuitry (20, 50, 52, 57, 80) provides a lower cut-in speed than cut-out speed. Simplified power supply and voltage detection circuitry is also disclosed.
76 Citations
7 Claims
-
1. In a single phase AC induction motor having a main winding and an auxiliary winding both connectable to an AC power source, and having a switch for disconnecting said auxiliary winding from said AC source, a control circuit for said switch comprising:
-
main voltage detector means sensing voltage from said AC source; auxiliary voltage detector means sensing auxiliary winding voltage; voltage comparator means having a first input connected to said main voltage detector means and a second input connected to said auxiliary voltage detector means and comparing said auxiliary winding voltage against said voltage from said AC source and outputting a turn-off signal causing said switch to disconnect said auxiliary winding from said AC source when said auxiliary winding voltage increases to a predetermined cut-out value relative to said voltage from said AC source as a function of motor speed, and outputting a turn-on signal causing said switch to connect said auxiliary winding to said AC source when said auxiliary winding voltage decreases to a predetermined cut-in value relative to said voltage from said AC source as a function of motor speed, said predetermined cut-in value corresponding to a voltage derived from rotationally induced voltage in said auxiliary winding during overload or stall of said motor after starting; hysteresis means responsive to said turn-off signal to change the voltage at one of said inputs of said comparator means such that said auxiliary winding voltage must decrease to a cut-in value which is less than said cut-out value before reconnection of said auxiliary winding to said AC source, wherein said hysteresis means comprises a connection between the output of said comparator means and said one input of said comparator means to adjust the voltage level at said one input according to said output. - View Dependent Claims (2, 3)
-
-
4. In a single phase AC induction motor having a main winding and an auxiliary winding both connectable to an AC power source, and having a switch for disconnecting said auxiliary winding from said AC source, a control circuit for said switch comprising:
-
main voltage detector means sensing voltage from said AC source; auxiliary voltage detector means sensing auxiliary winding voltage; a first voltage comparator having a first input connected to said main voltage detector means and a second input connected to said auxiliary voltage detector means and comparing said auxiliary winding voltage against said voltage from said AC source and outputting a turn-off signal when said auxiliary winding voltage increases to a predetermined cut-out value relative to said voltage from said AC source as a function of motor speed, and outputting a turn-on signal when said auxiliary winding voltage decreases to a predetermined cut-in value relative to said voltage from said AC source as a function of motor speed, said predetermined cut-in value corresponding to a voltage derived from rotationally induced voltage in said auxiliary winding during overload or stall of said motor after starting; a second voltage comparator connected to the output of said first comparator, said second comparator being responsive to said turn-off signal from said first comparator to output a turn-off signal to said switch to disconnect said auxiliary winding from said AC source, said second comparator being responsive to said turn-on signal from said first comparator to output a turn-on signal to said switch to connect said auxiliary winding to said AC source; means connecting said output of said first comparator to one of said inputs of said first comparator to change the voltage at said one input of said first comparator according to the voltage at said output of said first comparator such that the voltage at the other input of said first comparator is compared against different voltages at said one input of said first comparator according to the output state of said first comparator, the voltage at said other input of said first comparator being compared against a first voltage at said one input of said first comparator when said first comparator is outputting said turn-off signal, the voltage at said other input of said first comparator being compared against a second voltage at said one input of said first comparator when said first comparator is outputting said turn-on signal, and wherein said first voltage at said one input of said first comparator is higher than said second voltage at said one input of said first comparator such that said auxiliary winding voltage must decrease to a cut-in value which is less than said cut-out value before said output of said first comparator changes states to output said turn-on signal to said second comparator to reconnect said auxiliary winding to said AC source, wherein said second comparator has a first input connected to said first input of said first comparator, and has a second input connected to said output of said first comparator, and comprising a resistor connected between said inputs of said second comparator to provide a voltage drop therebetween, and wherein said output of said first comparator is connected through said resistor to said first input of said first comparator to change the voltage at said first input of said first comparator according to the voltage at said output of said first comparator. - View Dependent Claims (5, 6)
-
-
7. In a single phase AC induction motor having a main winding and an auxiliary winding both connectable to an AC power source, and having a switch for disconnecting said auxiliary winding from said AC source, a control circuit for said switch comprising:
-
main voltage detector means sensing voltage from said AC source; auxiliary voltage detector means sensing auxiliary winding voltage; voltage comparator means having a first input connected to said main voltage detector means and a second input connected to said auxiliary voltage detector means and comparing said auxiliary winding voltage against said voltage from said AC source and outputting a turn-off signal causing said switch to disconnect said auxiliary winding from said AC source when said auxiliary winding voltage increases to a predetermined cut-out value relative to said voltage from said AC source as a function of motor speed, and outputting a turn-on signal causing said switch to connect said auxiliary winding to said AC source when said auxiliary winding voltage decreases to a predetermined cut-in value relative to said voltage from said AC source as a function of motor speed, said predetermined cut-in value corresponding to a voltage derived from rotationally induced voltage in said auxiliary winding during overload or stall of said motor after starting; hysteresis means responsive to said turn-off signal to change the voltage at one of said inputs of said comparator means such that said auxiliary winding voltage must decrease to a cut-in value which is less than said cut-out value before reconnection of said auxiliary winding to said AC source.
-
Specification