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Electronic motor starter

  • US 4,967,131 A
  • Filed: 08/15/1989
  • Issued: 10/30/1990
  • Est. Priority Date: 08/16/1988
  • Status: Expired due to Term
First Claim
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1. An electronic motor starter for use with a single-phase induction motor having a starting winding comprising:

  • a triac having a first terminal connected to a motor power source, a second terminal connected to the starting winding, and a gate terminal;

    a rectifying means (7) including a first diode (D2) connected to the first terminal of the triac and a first capacitor (C4) for rectifying the power source;

    a gate powering means (8) having first and second distribution resistors (R7) and (R8) connected to the rectifying means, a Zener diode (ZD) and a first filter capacitor (C2) each connected in parallel to the second distribution resistor (R8) to supply a gate powering voltage;

    a signal voltage detecting means (9) across the starting winding having a second diode (D1), third and fourth distribution resistors (R1 and R2), and a second filter capacitor (C1);

    a hysteresis adjusting means (10) including a hysteresis adjusting resistor (R3) connected to the junction of the third distribution hysteresis adjusting resistors (R1 and R3), first and second NAND gates M1 and M2 and a feedback resistor (R4);

    an oscillating means (11) connected between the first and second NAND gates (M1 and M2) including third and fourth NAND gates (M3 and M4), a first resistor (R5), and a second capacitor (C3); and

    a trigger means (12) comprised of a second resistor (R6) connected to the output of a fourth NAND gate (M4), a transistor (TR) having a base terminal connected to the second resistor (R6), an emitter terminal connected to ground and a collecter terminal, and a pick-up coil (PC) connected among the emitter terminal of the transistor (TR), the rectifying means (7) and the gate terminal of the triac, whereby the pickup coil (PC) initially activates the triac to electrically connect the starting winding until an induced voltage across the winding reaches a predetermined value and thereafter deactivates the triac to disconnect the starting winding from the motor circuitry allowing a normal operation of the motor.

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