Start switch for a single phase AC motor

• US 4,651,077 A
• Filed: 06/17/1985
• Issued: 03/17/1987
• Est. Priority Date: 06/17/1985
• Status: Expired due to Fees

• Current Assignee: Ronald D. Woyski
• Original Assignee: Ronald D. Woyski
• Inventors: Woyski, Ronald D.
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): Logan, Sharon D.
• Application Number:
  US06/745,850
• Time in Patent Office: 638 Days
• Field of Search: 318/785, 318/786, 318/787, 318/788, 318/789, 318/790, 318/781, 307/140
• US Class Current: 318/781
• CPC Class Codes: H02P 1/44 by phase-splitting with a capacitor

Abstract

A start switch is provided for a single phase AC motor having a start winding and a start capacitor connected in series with the start winding and a main winding connected in parallel with the start winding and start capacitor. The AC motor is connectable with an AC power source in order to supply AC main winding voltage to the main winding and AC start winding voltage to the start winding. The start switch includes conductors connected with the main winding for sensing the AC main winding voltage and conductors connected with the start winding for sensing the AC start winding voltage. Phase sensor circuitry is employed to sense a difference in voltage phase between the start winding voltage and the main winding voltage. Detector circuitry is connected with the phase sensor circuitry to detect when the difference in the voltage phase reaches a threshold. An AC switch is connected in series with the start capacitor and the start winding to connect and disconnect the start winding and start capacitor to and from the AC power source. Actuator circuitry for the AC switch is responsive to the detector circuitry for actuating the AC switch to disconnect the start winding and the start capacitor from the AC power source when the difference in voltage phase reaches the threshold.

Claims

1. A start switch for a single phase AC motor having a start winding and a start capacitor connected in series with said start winding, a main winding connected in parallel with the start winding and start capacitor, and supply means for connecting the windings and capacitor with a single-phase AC power source to supply AC main winding voltage to the main winding and AC start winding voltage to the start winding, the start switch comprising:

(a) first sensing means connected with the main winding for sensing the AC main winding voltage;

(b) second sensing means connected with the start winding for sensing the AC start winding voltage;

(c) phase sensor means connected with the first and second sensing means for sensing a difference in voltage phase between the start winding voltage and the main winding voltage, said phase sensor means having output means for producing an output signal having a magnitude dependent on the difference in the voltage phase, the mangitude of the output signal reaching a predetermined limit when said difference in voltage phase reaches a selected threshold;

(d) detector means connected with the phase sensor means for detecting when the difference in the voltage phase reaches the threshold, said detector means having means for detecting when the magnitude of the output signal reaches the predetermined limit;

(e) switch means connected in series with the start capacitor and the start winding operable to connect and disconnect the start winding and the start capacitor to and from the AC power source; and

(f) actuator means for the switch means responsive to the detector means for actuating said switch means to disconnect the start winding and the start capacitor from the AC power source when the magnitude of the output signal reaches the predetermined limit.

2. The start switch in accordance with claim 1 wherein the detector means includes (a) a detector switch having a conductive state and a non-conductive state and trigger means for triggering the detector switch to change between the conductive and non-conductive states;

and (b) threshold detection means connected with the trigger means and output means for sensing when the magnitude of the output signal reaches the predetermined limit to enable the trigger means to trigger the detector signal to change states.

3. The start switch in accordance with claim 2 wherein said detector switch includes a switching transistor having a gate and conductive and non-conductive states and said trigger means includes the gate of the transistor and said threshold detection means comprises a zener diode having a breakdown voltage for triggering the switching transistor between the non-conductive and conductive states when the magnitude of the output signal reaches the predetermined limit.

6. The start switch in accordance with claim 1 wherein the switch means includes a triac having main terminals connected in series with the start winding and start capacitor and a gate connected with the actuator means for triggering the triac into a conductive state and for preventing the triggering of the triac into a conductive state when the difference in voltage phase reaches the threshold.

7. The start switch in accordance with claim 6 wherein the switch means includes a resistor and a capacitor connected in series across the main terminals of the triac.

4. A start switch for a single phase AC motor having a start winding and a start capacitor connected in series with said start winding, a main winding connected in parallel with the start winding and start capacitor, and supply means for connecting the windings and capacitor with a single-phase AC power source to supply AC main winding voltage to the main winding and AC start winding voltage to the start winding, the start switch comprising:

(a) first sensing means connected with the main winding for sensing the AC main winding voltage;

(b) second sensing means connected with the start winding for sensing the AC start winding voltage;

(c) phase sensor means connected with the first and second sensing means for sensing a difference in voltage phase between the start winding voltage and the main winding voltage, said phase sensor means having first rectifier means connected with the first sensing means for rectifying the AC main winding voltage to produce a DC main winding voltage;

second rectifier means connected with the second sensing means for rectifying the AC start winding voltage to produce a DC start winding voltage; and

output means for combining the DC main winding voltage and the DC start winding voltage to produce a composite DC output signal having a magnitude dependent on the difference in the voltage phase, the magnitude reaching a predetermined limit when said difference in voltage phase reaches a threshold;

(d) detector means connected with the phase sensor means for detecting when the difference in the voltage phase reaches the threshold, said detector means having means for detecting when the magnitude of the output signal reaches the predetermined limit;

(e) means connected in series with the start capacitor and the start winding operable to connect and disconnect the start winding and the start capacitor to and from the AC power source; and

(f) actuator means for the switch means responsive to the detector means for actuating said switch means to disconnect the start winding and the start capacitor from the AC power source when the difference in the voltage phase reaches the threshold.

5. A start switch in accordance with claim 4 wherein said first rectifier means includes a diode bridge having AC input terminals connected with the first sensing means to receive the AC main winding voltage and DC terminals for producing the DC main winding voltage and said second rectifier means includes a diode bridge having AC input terminals connected with the second sensing means to receive the AC start winding voltage and DC output terminals for producing the DC start winding voltage and wherein said output means includes means for connecting the DC output terminals of the first bridge with the DC output terminals of the second bridge.

8. A start switch for a single phase AC motor having a start winding and a start capacitor connected in series with said start winding, a main winding connected in parallel with the start winding and start capacitor, and supply means for connecting the windings and capacitor with a single-phase AC power source to supply AC main winding voltage to the main winding and AC start winding voltage to the start winding, the start switch comprising:

(a) first sensing means connected with the main winding for senisng the AC main winding voltage;

(b) second sensing means connected with the start winding for sensing the AC start winding voltage;

(c) phase sensor means connected with the first and second sensing means for sensing a difference in voltage phase between the start winding voltage and the main winding voltage;

(d) detector means connected with the phase sensor means for detecting when the difference in the voltage phase reaches a threshold;

(e) switch means connected in series with the start capacitor and the start winding operable to connect and disconnect the start winding and the start capacitor to and from the AC power source, the switch means including a triac having main terminals connected in series with the start winding and the start capacitor and a gate for triggering the triac into a conductive state and for preventing the triggering of the triac into a conductive state; and

(f) actuator means for the switch means responsive to the detector means for actuating said switch means to disconnect the start winding and the start capacitor from the AC power source when the difference in the voltage phase reaches the threshold, the actuator means including (a) a switching transistor having main terminals and having a gate connected with the detector means; and

(b) circuitry means connected with the main terminals of the switching transistor and the gate of the triac, the switching transistor changing between conductive and non-conductive states in response to the detector means to operably trigger the triac to a conductive state, and to operably prevent the triggering of the traic to a conductive state when the difference in voltage phase reaches the threshold.

9. A start switch for a single phase AC motor having a start winding and a start capacitor connected in series with the said start winding, the main winding connected in parallel with the start winding and the start capacitor, and supply means for connecting the windings and the capacitor with a single-phase AC power source to supply AC main winding voltage to the main winding and AC start winding voltage to the start winding, the start switch comprising:

(a) first sensing means connected with the main winding for sensing the AC main winding voltage;

(b) second sensing means connected with the start winding for sensing the AC start winding voltage;

(c) phase sensor means connected with the first and second sensing means for sensing a difference in voltage phase between the start winding voltage and the main winding voltage, the phase sensor means including first rectifier means connected with the first sensing means for rectifying the AC main winding voltage to produce a DC main winding voltage;

second rectifier means connected with the second sensing means for rectifying the AC start winding voltage to produce a DC start winding voltage; and

output means for combining the DC main winding voltage and the DC start winding voltage to produce a composite DC output signal having a magnitude dependent on the difference in the voltage phase, the magnitude reaching a predetermined limit when said difference in voltage phase reaches a threshold;

(d) detector means connected with the output means for detecting when the difference in the voltage phase reaches the threshold, the detector means including a switching transistor having conductive and non-conductive states and a gate for switching the transistor between the conductive and non-conductive states and diode means connected with the gate of the transistor and the output means for sensing when the magnitude reaches the predetermined limit to trigger the gate of the transistor to change the state of the transistor;

(e) switch means connected in series with the start capacitor and the start winding operable to connect and disconnect the start winding and the start capacitor to and from the AC power source, the switch means comprising a triac having main terminals connected in series with the start winding and the start capacitor and a gate; and

(f) actuator means for the switch means responsive to the detector means for actuating the switch means to disconnect the start winding and the start capacitor from the AC power source when the difference in the voltage phase reaches the threshold, the actuator means including a switching transistor having main terminals and a gate connected with the switching transistor of the detector means, and circuitry means connected with the main terminals of the switching transistor of the actuator means and the gate of the triac, the switching transistor of the actuator means changing between non-conductive and conductive states in response to the change in state of the switching transistor of the detector means to operably prevent triggering of the triac through the circuitry means to a conductive state.