Energy Saving System and Method for Devices with Rotating or Reciprocating Masses

• US 20100320956A1
• Filed: 09/01/2010
• Published: 12/23/2010
• Est. Priority Date: 09/14/2007
• Status: Active Grant

• Current Assignee: Powerwise Group, Inc.
• Original Assignee: Powerwise Group, Inc.
• Inventors: Kelley, Paul H., Venkataraman, Vasan, Lumsden, John L.
• Granted Patent: US 8,823,314 B2
• Time in Patent Office: Days
• US Class Current: 318/799
• CPC Class Codes: F04B 35/04 the means being electric
• CPC Class Codes: H02P 23/24 Controlling the direction, e.g. clockwise or counterclockwise
• CPC Class Codes: H02P 27/02 using supply voltage with constant frequency and variable amplitude
• CPC Class Codes: H02P 6/182 using back-emf in windings
• CPC Class Codes: H02P 6/28 Arrangements for controlling current H02P6/10 takes precedence

Abstract

A system and method are provided for reducing the energy consumed by a pump jack electric motor by reducing the supply voltage to the motor when the motor would be generating energy in open loop mode. By substantially eliminating the energy generation mode, the braking action of the utility grid in limiting the acceleration of the motor and system that would otherwise occur is substantially removed. The motor and system will speed up, allowing the natural kinetic energy of the cyclic motion to perform part of the pumping action. A closed loop controller in electrical connection with the motor computes the necessary information from the observed phase angle between the voltage and current supplied to the motor. By reducing the supply voltage to the motor, the observed phase angle may be reduced to a target phase angle value. By allowing some current flow, primarily of a reactive nature, an observable feedback parameter may be used in the closed loop control system as an indication of the load condition, to which the closed loop motor controller may react, supplying power when needed, such as in the energy consumption mode. The electric motor may be effectively turned off, but without completely cutting the power to the motor. During both the energy consumption mode and the period that open loop energy generation would be occurring, the closed loop motor controller may reduce the observed phase angle to a target phase angle by reducing the supply voltage. Any further reduction in the observed phase angle below the target phase angle may be interpreted as an increase in motor load, to which the motor controller may respond by increasing the supply voltage to the motor until the target phase angle is once again reached.

Claims

1. A method of saving energy for a pump jack with a counterweight disposed with a well, comprising the steps of:

supplying voltage and current from an electric utility grid to an electric motor connected with the pump jack;

rotating the pump jack counterweight with said electric motor;

observing the phase angle between the voltage and current supplied to said motor;

comparing the observed phase angle with a target phase angle; and

reducing the supply voltage to said motor when the observed motor phase angle is greater than the target phase angle.

2. The method of claim 1, wherein the current comprising a real component and a reactive component, and wherein the step of reducing the supply voltage to said motor causing the current real component to substantially zero and the current reactive component greater than zero.

3. The method of claim 2, wherein the step of reducing still allowing sufficient current to observe the phase angle.

4. The method of claim 1, wherein the step of reducing causing the pump jack counterweight to rotate faster than the counterweight would rotate if there were no step of reducing.

5. The method of claim 1, further comprising the step of:

moving a tubular string connected with the pump jack in a substantially vertical direction in the well,

wherein the step of reducing causing said tubular string to move faster than said tubular string would move if there were no step of reducing.

6. The method of claim 1, wherein the step of reducing causing said motor to rotate faster than said motor would rotate if there were no step of reducing.

7. The method of claim 1, further comprising the steps of:

pumping a first fluid with a first fluid density at a first time;

reducing the supply voltage to said motor when the observed motor phase angle is greater than the target phase angle during the step of pumping the first fluid;

pumping a second fluid with a second fluid density at a second time; and

reducing the supply voltage to said motor when the observed motor phase angle is greater than the target phase angle during the step of pumping the second fluid.

8. The method of claim 1, further comprising the step of:

maintaining the observed phase angle substantially at the target phase angle.

9. The method of claim 8, further comprising the step of:

increasing the supply voltage to said motor when the observed phase angle less than the target phase angle.

10. The method of claim 1, wherein the target phase angle constant for all loads applied to said motor.

11. The method of claim 1, wherein the target phase angle a variable function of the load at any instant applied to said motor.

12. The method of claim 1, wherein the step of comparing performed by a closed loop motor controller in electrical connection with said motor.

13. A system for saving energy, comprising:

an electric motor connected with a pump jack having a counterweight; and

a closed loop controller in electrical connection with said motor for observing the phase angle between the voltage and current supplied to said motor, comparing the observed phase angle with a target phase angle, and reducing the voltage supplied to said motor when the observed phase angle greater than the target phase angle.

14. A method for saving energy for a pump jack connected with a tubular string in a well, comprising the steps of:

supplying voltage and current to a motor disposed with the pump jack, wherein the current having a real component and a reactive component;

reciprocating the tubular string in the well with said motor;

observing the phase angle between the voltage and current supplied to said motor;

comparing the observed phase angle with a target phase angle; and

reducing the supply voltage to said motor when the observed motor phase angle is greater than the target phase and causing the current real component to substantially zero and the current reactive component greater than zero.

15. The method of claim 14, wherein the step of reducing still allowing sufficient current to observe the phase angle.

16. The method of claim 14, wherein the step of reducing causing the tubular string to reciprocate faster than the tubular string would reciprocate if there were no step of reducing.

17. A method for saving energy for a pump jack having a counterweight, comprising the steps of:

supplying voltage and current from an electric utility grid to an electric motor connected with the pump jack;

rotating the pump jack counterweight with said electric motor;

observing the phase angle between the voltage and current supplied to said motor;

comparing the observed phase angle with a target phase angle; and

reducing the supply voltage to said motor when the observed motor phase angle greater than the target phase;

wherein the step of reducing causing the pump jack counterweight to rotate faster than the counterweight would rotate if there were no step of reducing.

18. The method of claim 17, wherein the current comprising a real component and a reactive component, and wherein the step of reducing the supply voltage to said motor causing the current real component to substantially zero and the current reactive component greater than zero.

19. A method for saving energy for a pump jack having a counterweight disposed with a well, comprising the steps of:

supplying voltage and current to an electric motor in electrical connection with the pump jack;

controlling said electric motor with a closed loop controller;

rotating the pump jack counterweight with said electric motor; and

reducing the supply voltage to said motor with said closed loop controller when said motor would otherwise be generating energy if said motor were not being controlled with said closed loop controller.

20. The method of claim 19, wherein said electric motor would otherwise be generating energy if the phase angle between the voltage and current supplied to the motor operated in open loop would be greater than 90 degrees.

21. The method of claim 19, wherein the current comprising a real component and a reactive component, and wherein the step of reducing the supply voltage to said motor causing the current real component to substantially zero and the current reactive component greater than zero.

22. The method of claim 19, further comprising the steps of:

observing the phase angle between the voltage and current supplied to said motor; and

maintaining a target phase angle between the voltage and current supplied to said motor.

23. The method of claim 22, further comprising the step of:

increasing the supply voltage to said motor when the observed phase angle less than the target phase angle.