Pt Components, Inc.

Richard A Wrege

Victor A Murn

Steven F Chmiel

Dennis K Lorenz

In a single phase AC induction motor having a main winding (1) and an auxiliary winding (2) both connectable to an AC power source (4), and having a start switch (6, 74) for automatically connecting and disconnecting the auxiliary winding (2) to and from the AC source (4) in starting and running modes, respectively, and having a user operated reversing switch (207-212) for reversing the voltage polarity applied from the AC source (4) to one of the windings relative to the other winding, low cost circuitry is provided for detecting the polarity reversal by sensing when one of the main and auxiliary winding voltages shifts from a leading to a lagging position relative to the other winding voltage, whereupon the circuit automatically instantly reconnects the auxiliary winding (2) to the AC source (4) to immediately apply reverse torque. A first voltage comparator (221) senses a given polarity and magnitude of main winding voltage, and a second voltage comparator (222) senses a given polarity and magnitude of auxiliary winding voltage. The output of the second comparator (222) is differentiated (282), and a third voltage comparator (223) compares output pulses (270) from the first comparator (221) and differentiated output pulses (288) from the second comparator (222) and instantaneously senses polarity reversal when one of the pulses shifts relative to the other, and in turn actuates the start switch (6, 74).

Low cost instant reversing circuit

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).

Quick discharge motor starting circuit

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 quad comparator chip (61-64) senses and compares relative magnitudes of main and auxiliary winding voltages (30, 32 and 42) to de-energize the auxiliary winding (2) at cut-out speed, and automatically re-energize the auxiliary winding (2) at cut-in speed to accelerate or restart the motor from a stall or overload condition. Simplified power supply and voltage detection circuitry is also disclosed.

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Muskego, WI, United States of America

Richard A Wrege