Starting device and circuit for starting single phase motors

• US 5,561,357 A
• Filed: 04/24/1995
• Issued: 10/01/1996
• Est. Priority Date: 04/24/1995
• Status: Expired due to Term

• Current Assignee: Rectorseal Corporation (CSW Industrials, Inc.)
• Original Assignee: Fritz H. Schroeder
• Inventors: Schroeder, Fritz H.
• Primary Examiner(s): Ro, Bentsu
• Application Number:
  US08/427,572
• Time in Patent Office: 526 Days
• Field of Search: 318/778, 318/781, 318/785, 318/786, 318/787, 318/789, 318/790, 318/794
• US Class Current: 318/789
• CPC Class Codes: H02P 1/44 by phase-splitting with a capacitor

Abstract

An auxiliary capacitance starting device is connected by only two wires to a capacitor start-induction run (CSIR) or permanent split capacitor (PSC) motor. The device includes an auxiliary start capacitor and an electro-mechanical switching relay that has a current sensing coil wound over a voltage sensing coil and a set of normally closed contacts. The relay is energized first by a current level (amperage) and then latches into an energized mode by voltage, necessarily in that order. The auxiliary start capacitor is electrically connected to the motor circuit in parallel to the start and run winding by two non-polarized leads and in series with the current sensing coil. The voltage sensing coil is connected across the normally closed contacts and senses no voltage as long as the contacts are closed. As the motor gains speed (RPM), the current (amperage) increase through the current sensing coil and when it reaches a preset threshold, the current sensing coil opens the contacts which have a voltage across them when opening which voltage is sensed by the voltage sensing coil of the relay and latches the relay contacts open until power to the motor is removed. The components and circuitry are enclosed in a housing which may be easily mounted on a suitable surface in close proximity to the motor. The relay also prevents damage to the motor and/or auxiliary start capacitor from overloading due to high amperage caused by severe starting loads or adverse line voltage conditions.

Claims

1. An auxiliary starting circuit adapted to be connected by only two interchangeable wires to a single phase motor having a start winding and a run winding, comprising:

an integral electro-mechanical switching relay circuit adapted to be placed electrically in parallel with the existing start and run windings when the motor is started, said switching relay circuit sensing both amperage and voltage and including an auxiliary start capacitor and normally closed contacts, and being preset to open said normally closed contacts upon sensing amperage representing maximum RPM of the motor and upon said contacts being opened to sense voltage and maintain said contacts in the open position;

said switching relay circuit becoming energized upon detection of amperage representing full motor speed to open said normally closed contacts and disconnect the electrical connection between said auxiliary start capacitor and the start and run windings of the motor, and the instant said contacts are opened, sensing the voltage across the start and run terminals of the motor less the voltage drop across the auxiliary start capacitor and becoming energized to maintain said contacts in the open position as long as power is applied to the motor and becoming de-energized upon detection of no voltage to close said contacts and reconnect said auxiliary start capacitor to allow the re-application of electrical power to the start and run windings of the motor for starting the motor through the auxiliary starting circuit.

2. The auxiliary starting circuit according to claim 1 wherein

said electro-mechanical switching relay circuit has a current sensing coil connected in series with said auxiliary start capacitor and said normally closed contacts, said series connected auxiliary start capacitor, normally closed contacts and current sensing coil adapted to be connected in parallel across the existing start and run windings of the motor and said current sensing coil being preset to open said normally closed contacts upon sensing amperage representing maximum RPM of the motor;

and

a voltage sensing coil around which said current sensing coil is wound, said voltage sensing coil electrically connected in parallel across said normally closed contacts to sense no voltage when said normally closed contacts are closed and upon said contacts being opened said voltage sensing coil sensing the voltage across the start and run windings of the motor less the voltage drop across said auxiliary start capacitor.

3. The auxiliary starting circuit according to claim 2 wherein

said current sensing coil becomes energized upon detection of amperage representing full motor speed to open said normally closed contacts and disconnect the electrical connection between said auxiliary start capacitor and the start and run windings of the motor, and

the instant said normally closed contacts are opened, said voltage sensing coil senses the voltage across the start and run terminals of the motor less the voltage drop across the auxiliary start capacitor and becomes energized to maintain said normally closed contacts in the open position as long as power is applied to the motor and becomes de-energized upon detection of no voltage to close said normally closed contacts and reconnect said auxiliary start capacitor to allow the reapplication of electrical power to the start and run terminals of the motor for starting the motor through the auxiliary starting circuit.

4. The auxiliary starting circuit according to claim 2 wherein

said voltage sensing coil and said current sensing coil wound therearound has a ferrous metal core, and

said current sensing coil induces a magnetic field in said ferrous metal core upon the amperage reaching a preset threshold which is near the maximum RPM of the motor to open said normally closed contacts.

5. The auxiliary starting circuit according to claim 2 wherein

said series connected auxiliary start capacitor, normally closed contacts, and current sensing coil are adapted to be electrically connected in parallel between the start terminal and run terminal of the motor, and

said voltage sensing coil is connected in parallel across said normally closed contacts.

6. The auxiliary starting circuit according to claim 2 wherein

said single phase motor includes a run capacitor electrically connected in parallel with the start and run windings of the motor,

said series connected auxiliary start capacitor, normally closed contacts, and current sensing coil are adapted to be electrically connected in parallel with the run capacitor of the motor, and

said voltage sensing coil is connected in parallel across said normally closed contacts.

7. A method for starting a single phase motor having a start winding and a run winding through an auxiliary starting circuit comprising the steps of:

surrounding a voltage sensing coil with a current sensing coil;

electrically connecting an auxiliary start capacitor and a set of normally closed contacts in series with said current sensing coil, said current sensing coil being preset to open said normally closed contacts upon sensing amperage representing maximum RPM of the motor;

electrically connecting said voltage sensing coil in parallel across said set of normally closed contacts to sense no voltage when said normally closed contacts are closed and to detect voltage upon said contacts being opened;

electrically connecting said series connected auxiliary start capacitor, current sensing coil and normally closed contacts in parallel with the start and run windings of the motor; and

applying electrical power to the common and run terminals of the motor;

whereby

said current sensing coil becomes energized upon detection of amperage representing full motor speed to open said normally closed contacts and disconnect the electrical connection between said auxiliary start capacitor and the start and run windings; and

the instant said contacts are opened, said voltage sensing coil detects the voltage across the start and run terminals of the motor less the voltage drop across the auxiliary start capacitor and becomes energized to maintain said contacts in the open position as long as power is applied to the motor and becomes de-energized upon detection of no voltage to close said contacts and reconnect said auxiliary start capacitor to allow the re-application of electrical power to the start and run windings of the motor for starting the motor through the auxiliary starting circuit.

8. The starting method according to claim 7 wherein

said series connected auxiliary start capacitor, normally closed contacts, and current sensing coil comprise a series circuit having two wires extending therefrom, and

said step of electrically connecting said series connected auxiliary start capacitor, normally closed contacts and current sensing coil in parallel with the start and run windings of the motor comprises connecting either of the wires to the start terminal of the motor and the other wire to the run terminal of the motor.

9. The starting method according to claim 8 wherein

said single phase motor includes a run capacitor electrically connected in parallel with the start and run windings of the motor, and

said step of electrically connecting said series connected auxiliary start capacitor, normally closed contacts and current sensing coil in parallel with the start and run windings of the motor comprises connecting either of the wires to one terminal of the run capacitor and the other wire to another terminal of the run capacitor of the motor.

10. An auxiliary starting device adapted to be connected by only two interchangeable wires to a single phase motor having a start winding and a run winding, the device comprising;

an integral electro-mechanical switching relay circuit adapted to be placed electrically in parallel with the existing start and run windings when the motor is started, said switching relay circuit sensing both amperage and voltage and including an auxiliary start capacitor and normally closed contacts, and being preset to open said normally closed contacts upon sensing amperage representing maximum RPM of the motor and upon said contacts being opened to sense voltage and maintain said contacts in the open position;

a pair of non-polarized wire leads each having one end connected to said switching relay circuit and a free end, and said wire leads being interchangeably electrically connected in parallel with the start and run windings of the motor;

said switching relay circuit becoming energized upon detection of amperage representing full motor speed to open said normally closed contacts and disconnect the electrical connection between said auxiliary start capacitor and the start and run windings of the motor, and the instant said contacts are opened, sensing the voltage across the start and run terminals of the motor less the voltage drop across the auxiliary start capacitor and becoming energized to maintain said contacts in the open position as long as power is applied to the motor and becoming de-energized upon detection of no voltage to close said contacts and reconnect said auxiliary start capacitor to allow the re-application of electrical power to the start and run windings of the motor for starting the motor through the auxiliary starting device.

11. The auxiliary starting device according to claim 10 wherein

said electro-mechanical switching relay circuit has a current sensing coil connected in series with said auxiliary start capacitor and said normally closed contacts, said series connected auxiliary start capacitor, normally closed contacts and current sensing coil adapted to be connected in parallel across the existing start and run windings of the motor and said current sensing coil being preset to open said normally closed contacts upon sensing amperage representing maximum RPM of the motor;

and

a voltage sensing coil around which said current sensing coil is wound, said voltage sensing coil electrically connected in parallel across said normally closed contacts to sense no voltage when said normally closed contacts are closed and upon said contacts being opened said voltage sensing coil sensing the voltage across the start and run windings of the motor less the voltage drop across said auxiliary start capacitor.

12. The auxiliary starting device according to claim 11 wherein

said current sensing coil becomes energized upon detection of amperage representing full motor speed to open said normally closed contacts and disconnect the electrical connection between said auxiliary start capacitor and the start and run windings of the motor, and

the instant said normally closed contacts are opened, said voltage sensing coil senses the voltage across the start and run terminals of the motor less the voltage drop across the auxiliary start capacitor and becomes energized to maintain said normally closed contacts in the open position as long as power is applied to the motor and becomes de-energized upon detection of no voltage to close said normally closed contacts and reconnect said auxiliary start capacitor to allow the reapplication of electrical power to the start and run terminals of the motor for starting the motor through the auxiliary starting device.

13. The auxiliary starting device according to claim 11 wherein

said voltage sensing coil and said current sensing coil wound therearound has a ferrous metal core, and

said current sensing coil induces a magnetic field in said ferrous metal core upon the amperage reaching a preset threshold which is near the maximum RPM of the motor to open said normally closed contacts.

14. The auxiliary starting device according to claim 11 wherein

said pair of wire leads are adapted to be interchangeably electrically connected in parallel to the start terminal and run terminal of the motor.

15. The auxiliary starting device according to claim 11 wherein

the single phase motor includes a run capacitor electrically connected in parallel with the start and run windings of the motor, and

the free ends of said pair of wire leads are adapted to be interchangeably electrically connected in parallel with the run capacitor of the motor.

16. The auxiliary starting device according to claim 10 wherein

said integral electro-mechanical switching relay circuit is mounted within a single housing with said pair of wire leads extending outwardly therefrom.

17. The auxiliary starting device according to claim 16 wherein

said single housing is provided with mounting means for mounting said housing to a suitable surface in close proximity to the motor.

18. An integral electro-mechanical switching relay circuit for use in an auxiliary capacitance starting circuit to sense both amperage and voltage for starting a single phase motor having a start winding and a run winding comprising;

a voltage sensing coil surrounded by a current sensing coil;

an auxiliary start capacitor and a set of normally closed contacts electrically connected in series with said current sensing coil, said current sensing coil being preset to open said normally closed contacts upon sensing amperage representing maximum RPM of the motor;

said voltage sensing coil being electrically connected in parallel across said set of normally closed contacts to sense no voltage when said normally closed contacts are closed and to detect voltage upon said contacts being opened;

said series connected auxiliary start capacitor, current sensing coil and normally closed contacts adapted to be electrically connected in parallel with the start and run windings of the motor; and

said current sensing coil becoming energized upon detection of amperage representing full motor speed to open said normally closed contacts and disconnect the electrical connection between said auxiliary start capacitor and the start and run windings of the motor; and

the instant said normally closed contacts are opened, said voltage sensing coil sensing the voltage across the start and run terminals of the motor less the voltage drop across the auxiliary start capacitor and becoming energized to maintain said contacts in the open position as long as power is applied to the motor and becoming de-energized upon detection of no voltage to close said contacts and reconnect said auxiliary start capacitor to allow the re-application of electrical power to the start and run terminals of the motor for starting the motor through the auxiliary capacitance starting circuit.