Switch assembly, electric machine having the switch assembly, and method of controlling the same

• US 20050158177A1
• Filed: 03/16/2005
• Published: 07/21/2005
• Est. Priority Date: 07/09/2003
• Status: Active Grant

• Current Assignee: A. O. Smith Corporation
• Original Assignee: A. O. Smith Corporation
• Inventors: Mehlhorn, William L.
• Granted Patent: US 7,183,741 B2
• Time in Patent Office: Days
• US Class Current: 417/44.110
• CPC Class Codes: F04D 15/0218 the condition being a liquid level or a lack of liquid supply
• CPC Class Codes: G01F 23/266 measuring circuits therefor
• CPC Class Codes: H02P 1/42 for starting an individual single-phase induction motor H02P27/04 takes precedence
• CPC Class Codes: H02P 1/44 by phase-splitting with a capacitor
• CPC Class Codes: H03K 17/08 Modifications for protecting switching circuit against overcurrent or overvoltage
• CPC Class Codes: H03K 17/292 in thyristor, unijunction transistor or programmable unijunction transistor switches
• CPC Class Codes: H03K 17/305 in thyristor switches
• CPC Class Codes: H03K 17/725 for ac voltages or currents H03K17/722, H03K17/735 take precedence

Abstract

A pump assembly for pumping a liquid and a method of controlling the pump assembly. The pump assembly includes a motor coupled to a pump, and an electronic switch assembly electrically connected to the motor to control the current through the motor. The electronic switch assembly includes an electronic switch, a generator that provides a substantially periodic pulsing signal, a circuit control configured to provide a second signal, and decision logic connected to the generator, the circuit control, and the electronic switch. The decision logic receives the periodic pulsing and second signals and generates a control signal that selectively controls the electronic switch based on the periodic pulsing and second signals.

Claims

1. A pump assembly for pumping a liquid with a pump, the pump assembly comprising:

a motor coupled to the pump; and

an electronic switch assembly electrically connected to the motor to control the current through the motor, the electronic switch assembly comprising

an electronic switch,

a generator that provides a substantially periodic pulsing signal,

a circuit control configured to provide a second signal, and

decision logic connected to the generator, the circuit control, and the electronic switch, the decision logic receiving the periodic pulsing and second signals and generating a control signal that selectively controls the electronic switch based on the periodic pulsing and second signals.

2. A pump assembly as set forth in claim 1 wherein the electronic switch comprises a triac.

3. A pump assembly as set forth in claim 1 wherein the circuit control further comprises a voltage sense circuit comprising a sensor that senses the voltage across the electronic switch.

4. A pump assembly as set forth in claim 3 wherein the pulses have a relation to the zero crossings of the sensed voltage.

5. A pump assembly as set forth in claim 1 wherein the circuit control includes a delay preventing the closing of the switch during a time period.

6. A pump assembly as set fourth in claim 1 wherein the circuit control includes a sensor that senses a parameter relating to the liquid, the circuit control providing a second signal based on the sensed parameter,

7. A pump assembly as set forth in claim 6 wherein the sensor comprises a liquid-level sensor, and wherein the second signal is based on the level of the liquid to be pumped.

8. A pump assembly as set forth in claim 7 wherein the liquid-level sensor comprises a capacitance sensor comprising a reference plate and a first plate, and wherein the second sign al instructs the decision logic to control the electronic switch to a conductive state when the liquid covers both the reference plate and the first plate.

9. A pump assembly as set forth in claim 1 wherein the periodic pulsing signal comprises a first pulse state and a first non-pulsed state, wherein the second signal comprises first and second states, and wherein the control signal comprises a second pulsing signal comprising a second pulse state and a second non-pulsed state, and wherein the second pulsing signal is in the second pulse state when the periodic pulsing signal is in the first pulse state, the second signal is in the first state, and zero or more other conditions occur.

10. A pump assembly as set forth in claim 9 wherein the second pulsing signal is in the second non-pulsed state when the periodic pulsing signal is in the first non-pulsed state and zero or more other conditions occur.

11. A pump assembly as set forth in claim 10 wherein the second pulsing signal is in the second non-pulsed state when the second signal is in the second state and zero or more other conditions occur.

12. A pump assembly for pumping a liquid, the pump assembly comprising:

a pump;

a motor coupled to the pump; and

an electronic switch assembly electrically connected to the motor to control the current through the motor, the electronic switch assembly comprising

an electronic switch,

a voltage sense circuit comprising a sensor that senses the voltage across the electronic switch;

a generator that provides a substantially periodic pulsing signal, the generator pulsing the signal based on the zero crossings of the sensed voltage,

a circuit control comprising a liquid-level sensor and being configured to generate a second signal based on the level of the liquid to be pumped, and

decision logic connected to the generator, the circuit control, and the electronic switch, the decision logic receiving the periodic pulsing and second signals and generating a control signal that selectively controls the electronic switch based on the periodic pulsing and second signals.

13. A pump assembly as set forth in claim 12 wherein the periodic pulsing signal comprises first pulses and first non-pulsed states, wherein the second signal comprises first and second states, and wherein the control signal comprises a second pulsing signal comprising second pulses and second non-pulsed states, wherein the decision logic generates one of the second pulses when the generator generates one of the first pulses, the second signal is in the first state, and zero or more other conditions occur, wherein the second pulsing signal is in one of the second non-pulsed states when the periodic pulsing signal is in one of the first non-pulsed state and zero or more other conditions occur, and wherein the second pulsing signal is in one of the second non-pulsed states when the second signal is in the second state and zero or more other conditions occur, and wherein the electronic switch conducts current based on the second pulsing signal.

14. A method of controlling current to a pump motor of a pump with an electronic switch, the method comprising:

generating a substantially periodic pulsing signal comprising first pulses and first non-pulsed states;

generating a second signal comprising first states and second states;

generating a control signal comprising second pulses and second non-pulsed states, the generating of the control signal comprising

generating one of the second pulses when generating the periodic pulsing signal with one of the first pulses, generating the second signal in one of the first states, and zero or more other conditions occur,

generating the control signal in one of the second non-pulsed states when generating the periodic pulsing signal in one of the first non-pulsed states and zero or more other conditions occur, and

generating the control signal in one of the second non-pulsed states when generating the second signal in one of the second states and zero or more other conditions occur;

providing the control signal to the electronic switch;

initiating current through the electronic switch upon receiving a pulse in the control signal.

15. A method as set forth in claim 14 wherein the method further comprises connecting the electronic switch to a periodic power source and sensing a voltage across the electronic switch, and wherein generating the substantially periodic pulsing signal comprises generating the first pulses based on the zero crossings of the sensed voltage.

16. A method as set forth in claim 14 wherein the method further comprises sensing a level of a liquid to be pumped, and wherein generating the second signal comprises generating the second signal with one of the first states when the sensed level indicates the need to pump the liquid.

17. A liquid-level sensor to sense a liquid having a level with respect to an axis, the liquid level sensor comprising a circuit board having a first length, width, and height, the first height being along the axis, the circuit board comprising a first capacitive plate having a second length, width, and height, the second height being along the axis, a second capacitive plate having a third length, width, and height, the third height being along the axis, the third height being disposed above the second height, a notch disposed in the circuit board between the second and third heights, and a charge-transfer sensor coupled to the first and second capacitive plates.

18. A liquid level sensor as set forth in claim 17 wherein the first, second, and third lengths are orthogonal to the first, second, and third heights, and wherein the notch includes a fourth length greater than at least one of the second and third lengths.

19. A liquid level sensor as set forth in claim 18 wherein the fourth length is greater than both of the second and third lengths.

20. A liquid level sensor as set forth in claim 17 wherein the sensor further comprises a second circuit board having a fourth length, width, and height, the fourth height being along the axis and being disposed above the first height, the second circuit board comprising a third capacitive plate having a fourth length, width, and height, the fourth height being along the axis, and wherein the charge-transfer sensor couples to the third capacitive plate.