Control arrangement for single phase AC systems

• US 4,307,327 A
• Filed: 09/17/1979
• Issued: 12/22/1981
• Est. Priority Date: 09/17/1979
• Status: Expired due to Term

• Current Assignee: Franklin Electric Company Incorporated (EBW, Inc.)
• Original Assignee: Franklin Electric Company Incorporated (EBW, Inc.)
• Inventors: Streater, August L., Whitney, John A.
• Primary Examiner(s): Smith, Jr., David
• Assistant Examiner(s): Rubinson, Gene Z.
• Application Number:
  US06/076,498
• Time in Patent Office: 827 Days
• Field of Search: 318/786, 318/787
• US Class Current: 318/786
• CPC Class Codes: H02P 1/42 for starting an individual single-phase induction motor H02P27/04 takes precedence

Abstract

This disclosure relates to control apparatus and particularly to a triggered switch connected in a first or controlled circuit and a trigger device connected in a second circuit. AC currents flow through the first and second circuits and there is a changing phase angle between the currents. Further, the current level in the second circuit changes. When the phase angle is greater than a certain value and the current level in the second circuit is above a certain level, the trigger device triggers the switch and energizes the first circuit. At angles below the value and current levels below the certain level, the switch is not triggered. Thus, the changing phase angle may be utilized to control the first circuit. The triggered switch is a thyristor type of device such as a triac, and the trigger device is preferably a reed switch. The control apparatus is particularly useful in controlling the start winding of a single phase AC motor.

Claims

1. Apparatus for controlling the start winding of an AC motor comprising a main winding and a start winding connected in parallel, power lines connected to said windings and adapted to be connected to an AC power supply, bidirectional thyristor means connected in series with said start winding, and current responsive trigger means connected to said thyristor means for triggering said thyristor means to conduction, and said trigger means being connected to said power lines and responding to current flow though said lines and said motor windings.

2. Apparatus as in claim 1, wherein said trigger means comprises a reed switch including contacts, a coil, and a shading coil.

3. Apparatus as in claim 1, wherein said trigger means comprises a latching type reed switch.

24. Apparatus as in claim 1, wherein said thyristor means comprises a triac and said trigger means comprises a reed switch.

4. An AC motor comprising a main winding circuit and a start winding circuit connected in parallel, power lines adapted to be connected to an AC power supply and to supply main winding current and start winding current, bidirectional thyristor means connected in said start winding circuit and operable to conduct said start winding current by trigger current supplied thereto, and current responsive trigger means connected to said thyristor means to supply said trigger current and including excitation current carrying means connected in said power lines and receiving start winding current and main winding current, said trigger means having pick-up and drop-out excitation current levels and supplying said trigger current during that portion of an AC half cycle lying between the point at which said excitation current first exceeds said pick-up level and the point at which said excitation current decreases to below said drop-out level, and said thyristor means being triggered to conduction at the beginning of a half cycle of said start winding current when said beginning coincides in time with said portion of a half cycle and when the peak value of said excitation current exceeds said pick-up level.

5. Apparatus as in claim 4, wherein said trigger means comprises a reed switch including contacts, a coil connected in said power lines, and a shading coil.

6. Apparatus as in claim 4, wherein said trigger means comprises a latching reed switch.

7. Apparatus as in claim 4, wherein said trigger means comprises a reed switch including contacts, a first coil and a second coil, said first coil being connected in said power lines and said second coil being connected to carry said start winding current.

8. Apparatus as in claim 7, wherein the phase of said start winding current leads said excitation current by a phase angle at low motor speeds and said angle decreases as said motor speed increases, and said thyristor means is not triggered to conduction when said phase angle decreases to where said beginning is not in time coincidence with said portion of a half cycle.

9. Apparatus as in claim 4, wherein said thyristor means comprises a reed switch including a triac, and said trigger means comprises contacts connected in said start winding circuit and an excitation coil connected in said power lines.

11. Apparatus as in claim 9, wherein said reed switch comprises a latching type, and said drop-out excitation current level occurs approximately when said excitation current changes polarity.

13. Apparatus as in claim 9, wherein said motor is a dual-voltage type and includes two main windings.

10. Apparatus for controlling an AC motor having a main winding circuit and a start winding circuit connected in parallel, and power lines adapted to connect with an AC power supply and to supply main winding and start winding alternating currents, said apparatus comprising a triac adapted to be connected in said start winding circuit and to be triggered to conduct said start winding current by trigger current supplied thereto, a reed switch having contacts and an excitation coil, said contacts being connected to said triac to supply said trigger current, said reed switch having pick-up and drop-out excitation current levels in said coil and supplying said trigger current during a portion of each AC half cycle when said excitation current in said coil exceeds said pick-up level, and at motor speeds below the start winding cut-out speed said triac being triggered to conduction at the beginning of a half cycle of said start winding current when said beginning coincides in time with said portion of a half cycle and when said excitation current exceeds said pick-up level, said coil being adapted to respond to current flow through at least one of said motor windings, said excitation current in said coil producing magnetic excitation, and further including a shading coil adjacent said contacts for producing a time lag in said magnetic excitation.

12. Apparatus for controlling an AC motor having a main winding circuit and a start winding circuit connected in parallel, and power lines adapted to connect with an AC power supply and to supply main winding and start winding alternating currents, said apparatus comprising a triac adapted adapted to be connected in said start winding circuit and to be triggered to conduct said start winding current by trigger current supplied thereto, a reed switch having contacts and an excitation coil, said contacts being connected to said triac to supply said trigger current, said reed switch having pick-up and drop-out excitation current levels in said coil and supplying said trigger current during a portion of each AC half cycle when said excitation current in said coil exceeds said pick-up level, and at motor speeds below the start winding cut-out speed said triac being triggered to conduction at the beginning of a half cycle of said start winding current when said beginning coincides in time with said portion of a half cycle and when said excitation current exceeds said pick-up level, said coil being adapted to be connected to said power lines and to respond to line current flow, the phase of said line current in said coil lagging by a phase angle the phase of said start winding current in said triac at relatively low motor speeds and said angle decreasing as the motor speed increases, and said triac not being triggered to conduction when said angle decreases to where said beginning does not coincide with said portion, and a second excitation coil on said reed switch, said second excitation coil being adapted to carry said start winding current.

14. Apparatus for use in an AC system, comprising a first circuit and a second circuit, power lines connected to said first and second circuits for supplying AC currents thereto, a triggered switch connected in said first circuit, a reed switch including contacts, a first coil and a second coil, said contacts being connected to said triggered switch to actuate said switch, said first coil being connected in said first circuit and said second coil being connected in said second circuit, means in one of said first and second circuits for changing the relative phases and current levels of the AC currents therein, said contacts triggering the switch and energizing the first circuit only when the phase angle between the currents in the two circuits is greater than a certain value and the current level in the second circuit is above a certain level.

15. Apparatus as in claim 14, wherein said reed switch further includes a shading coil.

16. An AC motor comprising a main winding circuit and a start winding circuit connected in parallel, power lines adapted to be connected to an AC power supply and to supply main winding current and start winding current, bidirectional thyristor means connected in said start winding circuit and operable to conduct said start winding current by trigger current supplied thereto, and a reed switch including contacts connected to said thyristor means to supply said trigger current and including an excitation coil connected in said main winding circuit and receiving said main winding current, said reed switch further including a shading coil adjacent said contacts, said trigger means having pick-up and drop-out excitation current levels and supplying said trigger current during that portion of an AC half cycle lying between the point at which said excitation current first exceeds said pick-up level and the point at which said excitation current decreases to below said drop-out level, and said thyristor means being triggered to conduction at the beginning of a half cycle of said start winding current when said beginning coincides in time with said portion of a half cycle and when the peak value of said excitation current exceeds said pick-up level.

17. Apparatus as in claim 16, wherein said reed switch is a latching type.

18. A start winding cut-out circuit for a single phase AC motor including a main winding and a start winding connected in parallel and power lines for connecting the windings to an AC power supply, the main winding and line currents decreasing as the motor speed increases and the phase of the start winding current changing relative to the line current, the start winding current leading the line current at relatively low speeds and changing to a lagging condition at higher motor speeds, said circuit comprising a triac adapted to be connected in series with said starting winding, a reed switch having reed contacts and an exciting coil, said contacts being connected to supply trigger current to said triac when closed, said coil being adapted to be connected in said power lines to respond to current flow through said main and start windings, said reed switch having pick-up and drop-out levels of current flow through said coil and said coil current producing magnetic excitation for operating said contacts, and at motor speeds below the start winding cut-out speed the peak value of the coil current being greater than the pick-up level and said start winding current changing from one AC half cycle to the next AC half cycle while said reed contacts are closed.

19. A circuit as in claim 18, wherein said reed switch further includes a shading coil adjacent said exciting coil.

20. A circuit as in claim 18, wherein said reed switch is a latching type.

21. A circuit as in claim 18, wherein said reed switch further includes a second exciting coil adapted to be connected in series with said start winding.

22. An AC motor comprising a main winding circuit and a start winding circuit connected in parallel, power lines adapted to be connected to an AC power supply and to supply main winding current and start winding current, bidirectional thyristor means connected in said winding circuit and operable to conduct said start winding current by trigger current supplied thereto, and a latching type reed switch including contacts connected to said thyristor means to supply said trigger current and including as excitation coil connected in said main winding circuit and receiving said main winding current, said trigger means having pick-up and drop-out excitation current levels and supplying said trigger current during that portion of an AC half cycle lying between the point at which said excitation current first exceeds said pick-up level and the point at which said excitation current decreases to below said drop-out level, and said thyristor means being triggered to conduction at the beginning of a half cycle of said start winding current when said beginning coincides in time with said portion of a half cycle and when the peak value of said excitation current exceeds said pick-up level.

23. In an AC motor including a main winding and a start winding connected in parallel, said windings being adapted to be connected by power lines to an AC power supply whereby main winding current and start winding current flow through said windings at motor speeds below a start winding cut-out speed, said start winding current leading the line current in said power lines by a relatively large phase angle at relatively low motor speeds and said phase angle decreasing as the motor speed increases, the improvement comprising bidirectional thyristor means connected in series with said start winding and receiving said start winding current at said low speeds, and means connected in said power lines and receiving said line current and connected to said thyristor means for triggering said thyristor means to conduction at a predetermined phase angle between said start winding current and said line current.