Quick discharge motor starting circuit
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 start capacitor for providing a phase shifted field for starting torque, and having start switch means for automaticaly connecting and disconnecting said start capacitor to and from said AC source in starting and running modes, respectively, auxiliary switch means connected across said start capacitor for quickly discharging said start capacitor upon disconnection of said start capacitor from said AC source.
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Accused Products
Abstract
A motor starting control circuit is provided with an auxiliary switch (100), including a triac (102) and series resistor (114), connected across the start capacitor (5) for quickly discharging the start capacitor (5) upon disconnection of the start capacitor (5) from the AC source (4). This enables a lower rated start switch (6) by eliminating extra voltage thereacross caused by an otherwise charged start capacitor (5).
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Citations
10 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 start capacitor for providing a phase shifted field for starting torque, and having start switch means for automaticaly connecting and disconnecting said start capacitor to and from said AC source in starting and running modes, respectively, auxiliary switch means connected across said start capacitor for quickly discharging said start capacitor upon disconnection of said start capacitor from said AC source.
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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 start capacitor for providing a phase shifted field for starting torque, and having start switch means for automatically connecting and disconnecting said start capacitor to and from said AC source in starting and running modes, respectively, control circuitry comprising:
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auxiliary switch means connected across said start capacitor; main voltage detector means for sensing main winding voltage; auxiliary voltage detector means for sensing auxiliary winding voltage; voltage comparator means comparing main and auxiliary voltages from said main and auxiliary voltage detector means and turning off said start switch means when said auxiliary winding voltage rises to a given cut-out value relative to said main winding voltage as a function of motor speed corresponding to a given cut-out speed to disconnect said start capacitor from said AC source and also turning on said auxiliary switch means to discharge said start capacitor through said auxiliary switch means. - View Dependent Claims (5, 6, 7)
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8. 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 start capacitor for providing a phase shifted field for starting torgue, and having start switch means for automatically connecting and disconnecting said start capacitor to and from said AC source in starting and running modes, respectively, control circuitry comprising:
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main voltage detector means for sensing the magnitude of main winding voltage; auxiliary voltage detector means for sensing the magnitude of auxiliary winding voltage; a first voltage comparator responsive to said main and auxiliary voltage detector means and comparing auxiliary winding voltage against main winding voltage and outputting a turn-off signal when the magnitude of the auxiliary winding voltage increases to a given cut-out value relative to the magnitude of the main winding voltage as a function of motor speed corresponding to a given cut-out speed; a second voltage comparator responsive to said main and auxiliary voltage detector means and comparing auxiliary winding voltage against main winding voltage and outputting a turn-on signal when the auxiliary winding voltage decreases to a given cut-in value relative to the main winding voltage as a function of motor speed corresponding to a given cut-in speed, said given cut-in value being a stall or overload condition voltage derived from auxiliary winding voltage during running of said motor after starting, said given cut-in speed being less than said given cut-out speed; a third voltage comparator responsive to the output of said first voltage comparator to output a turn-off signal in response to said turn-off signal from said first voltage comparator; - View Dependent Claims (10)
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9. a fourth voltage comparator responsive to the output of said second voltage comparator and responsive to the output of said third voltage comparator, said fourth voltage comparator being responsive to said turn-off signal from said third voltage comparator to output a turn-off signal to said start switch means to disconnect said start capacitor from said AC source, said fourth voltage comparator being responsive to said turn-on signal from said second voltage comparator to output a turn-on signal to said start switch means to connect sa-d start capacitor to said AC source;
auxiliary switch means connected across said start capacitor, said turn-off signal from said third voltage comparator to said fourth voltage comparator providing a turn-on signal for said auxiliary switch means to discharge said start capacitor.
Specification