CONTROL SYSTEM FOR A PUMP

• US 20100034665A1
• Filed: 06/15/2006
• Published: 02/11/2010
• Est. Priority Date: 06/21/2005
• Status: Abandoned Application

• Current Assignee: Xylem Ip Holdings LLC (Xylem, Inc.)
• Original Assignee: Xylem Ip Holdings LLC (Xylem, Inc.)
• Inventors: Zhong, Zhiyong, Mökander, Jürgen
• Application Number:
  US11/993,787
• Publication Number:
  US 20100034665A1
• Time in Patent Office: Days
• US Class Current: 417/42
• CPC Class Codes: F04D 15/0066 by changing the speed, e.g. of the driving engine
• CPC Class Codes: F04D 15/0077 Safety measures F04D15/02 takes precedence
• CPC Class Codes: F04D 15/0218 the condition being a liquid level or a lack of liquid supply

Abstract

The present invention relates to pumps comprising variable frequency drive means and methods for operating such pumps. The inventive method for operating a pump (1) comprises the steps of obtaining values of operating parameters of the pump (1) indicating pump conditions, communicating said values of operating parameters from variable frequency drive means (2) to a control device (11), determining if a predetermined condition is fulfilled, communicating instructions from the control device (11) to the variable frequency drive means (2), based on the fulfillment of said predetermined condition. Furthermore, a computer program product loadable into a memory of a digital computer device, including software code portions for performing the inventive method, a pump (1), a pump system and a control device (11) for a pump are described.

Claims

1. A method for operating a pump (1) comprising a motor (9) and variable frequency drive means (2), the latter being arranged to control the operation of the motor (9) by being connected to said motor (9) and to a feeder cable of the pump (1), the variable frequency drive means (2) comprising a rectifier (5), an inverter (7) and a DC link (10) extending therebetween, furthermore the pump (1) is operatively connected to a control device (11), the method being characterized by the steps of:

obtaining values of operating parameters of the pump (1) indicating pump conditions, by means of sensing means (16), which is comprised as a part of said variable frequency drive means (2) and which is operatively connected to said DC link (10),

communicating said values of operating parameters from the variable frequency drive means (2) to the control device (11),

determining (44, 64, 84) by means of the control device (1) if a predetermined condition is fulfilled based on said obtained values of operating parameters, and

communicating instructions from the control device (11) to the variable frequency drive means (2), based on the fulfillment of said predetermined condition, in order to control the operation of the motor (9) in accordance with said pump conditions.

2. The method according to claim 1, wherein the step of obtaining values of operating parameters of the pump (1) comprises the step of:

obtaining values of at least one of the following operating parameters;

the DC link voltage level, the DC link current level, the torque of the motor (9), or the power of the motor (9).

3. The method according to claim 1, further comprising the step of:

detecting (44, 64, 84) a certain pump condition by using said at least one operating parameter.

4. The method according to claim 3, wherein said pump condition concerns the presence of liquid at an inlet of the pump (1).

5. The method according to claim 4, wherein the step of determining if a predetermined condition is fulfilled comprises the steps of:

running (42) the pump (1) at a first speed level for a predetermined period of time,

running (42) the pump (1) at a second speed level for a predetermined period of time, and

determining (44) if the power of the motor (9) is proportional to the cube of the speed of the motor (9), based on the values of operating parameters obtained by the sensing means (16) for the first speed level and the second speed level, respectively.

6. The method according to claim 4, wherein the communicated instructions from the control device (11) to the variable frequency drive means (2), are

run (48) the pump (1) at a desired speed level, if it is determined that the predetermined condition is fulfilled, or

stop (46) the operation of the pump (1) a predetermined period of time, if it is determined that the predetermined condition is not fulfilled.

7. The method according to claim 6, further comprising the steps of, if the pump (1) is ran at the desired speed level:

checking (50) the presence of liquid at an inlet of the pump (1) by,

obtaining values of operating parameters of the pump (1), by means of the sensing means (16),

communicating said values of operating parameters from the variable frequency drive means (2) to the control device (11),

determining by means of the control device (11) if a second predetermined condition is fulfilled based on said obtained values of operating parameters, and

communicating instructions from the control device (11) to the variable frequency drive means (2), based on the fulfillment of said second predetermined condition, in order to control the operation of the motor (9).

8. The method according to claim 7, wherein the step of determining if a second predetermined condition is fulfilled comprises the step of:

comparing (50) the obtained values of operating parameters with a predetermined reference level.

9. The method according to claim 7, wherein the communicated instructions from the control device (11) to the variable frequency drive means (2), are

run (48) the pump (1) at the desired speed level, if it is determined that the second predetermined condition is fulfilled, and

stop (52) the operation of the pump (1) a predetermined period of time, if it is determined that the second predetermined condition is not fulfilled.

10. The method according to claim 2, further comprising the step of:

maintaining the value of the at least one operating parameter at a substantially constant level.

11. The method according to claim 10, wherein the step of determining if a predetermined condition is fulfilled comprises the steps of:

running (62) the pump (1) at a desired speed level,

determining (64) if the power of the motor (9) is lower than a predetermined reference level of the power of the motor (9), based on the values of the power of the motor (9) obtained by the sensing means (16) for the desired speed level.

12. The method according to claim 10, wherein the communicated instructions from the control device (11) to the variable frequency drive means (2), are

run (62) the pump (1) at the desired speed level, if it is determined that the predetermined condition is not fulfilled, or

calculate (66) the speed of the motor (9) required to reach a predetermined reference level of the power of the motor (9), if it is determined that the predetermined condition is fulfilled, and

run the pump (1) at said calculated speed.

13. The method according to claim 12, further comprising the steps of, if the pump (1) is ran at the calculated speed:

comparing (68) the calculated speed of the pump (1) with a preset maximum speed of the pump (1), and

run (70) the pump (1) at said calculated speed, if the calculated speed is lower than the preset maximum speed, or

run (72) the pump (1) at said preset maximum speed, if the calculated speed is higher than the preset maximum speed.

14. The method according to claim 3, wherein said pump condition concerns clogging of the pump (1).

15. The method according to claim 14, wherein the step of determining if a predetermined condition is fulfilled comprises the steps of:

running (82) the pump (1) at a desired speed level,

determining (84) if the power of the motor (9) is higher than a predetermined reference level of the power of the motor (9), based on the values of the power of the motor (9) obtained by the sensing means (16) for the desired speed level.

16. The method according to claim 14, wherein the communicated instructions from the control device (11) to the variable frequency drive means (2), are

run (82) the pump (1) at the desired speed level, if it is determined that the predetermined condition is not fulfilled, or

run (86) the pump (1) reversely at a predetermined speed for a predetermined period of time, and

run the pump (1) in its normal operation direction at the desired speed level after said predetermined period of time of reverse operation, if it is determined that the predetermined condition is fulfilled.

17. The method according to claim 16, further comprising the steps of:

repeating (88) said step of determining if the power of the motor (9) is higher than a predetermined reference level of the power of the motor (9), and

repeating the steps according to claim 16.

18. The method according to claim 14, wherein the following steps are performed at regular intervals during the operation of the pump (1):

running the pump (1) reversely at a predetermined speed for a predetermined period of time, and

running the pump (1) in its normal operation direction at a desired speed level after said predetermined period of time of reverse operation.

19. Computer program product (14) loadable into a memory (13) of a digital computer device, including software code portions for performing the method of claim 1 when said computer program product (14) is ran on said digital computer device.

20. A pump comprising a motor (9) and variable frequency drive means (2), the latter being arranged to control the operation of the motor (9) by being connected to said motor (9) and to a feeder cable of the pump (1), the variable frequency drive means (2) comprising a rectifier (5), an inverter (7) and a DC link (10) extending therebetween, furthermore the pump (1) is operatively connected to a control device (11), characterized in that sensing means (16) is comprised as a part of said variable frequency drive means (2), which sensing means (16) is operatively connected to said DC link (10) and which is arranged to obtain values of operating parameters of the pump (1) indicating pump conditions, the variable frequency drive means (2) being arranged to communicate to the control device (11) said values of operating parameters, furthermore the control device (11) is arranged to determine if a predetermined condition is fulfilled based on said obtained values of operating parameters and to communicate instructions to the variable frequency drive means (2), based on the fulfillment of said predetermined condition, in order to control the operation of the motor (9) in accordance with said pump conditions.

21. The pump according to claim 20, wherein said control device (11) is adapted to obtain values of at least one of the following operating parameters:

the DC link voltage level, the DC link current level, the torque of the motor (9), or the power of the motor (9).

22. The pump according to claim 21, wherein said control device (11) is adapted to:

run the pump (1) at a first speed level for a predetermined period of time,

run the pump (1) at a second speed level for a predetermined period of time, and

determine if the power of the motor (9) is proportional to the cube of the speed of the motor (9), based on the values of the at least one operating parameter obtained by the sensing means (16) for the first speed level and the second speed level, respectively.

23. The pump according to claim 22, wherein said control device (11) is adapted to:

run the pump (1) at a desired speed level, if it is determined that the predetermined condition is fulfilled, or

stop the operation of the pump (1) a predetermined period of time, if it is determined that the predetermined condition is not fulfilled.

24. The pump according to claim 21, wherein the control device (11) is adapted to:

maintain the value of the at least one operating parameter at a substantially constant level.

25. The pump according to claim 24, wherein the control device (11) is adapted to:

run the pump (1) at a desired speed level,

determine if the power of the motor (9) is lower than a predetermined reference level of the power of the motor (9), based on the values of the power of the motor (9) obtained by the sensing means (16) for the desired speed level.

26. The pump according to claim 24, wherein the control device (11) is adapted to:

run the pump (1) at the desired speed level, if it is determined that the predetermined condition is not fulfilled, or

calculate (66) the speed of the motor (9) required to reach a predetermined reference level of the power of the motor (9), if it is determined that the predetermined condition is fulfilled, and

run the pump (1) at said calculated speed.

27. The pump according to claim 26, wherein the control device (11) is adapted to:

compare (68) the calculated speed of the pump (1) with a preset maximum speed of the pump (1), and

run (70) the pump (1) at said calculated speed, if the calculated speed is lower than the preset maximum speed, or

run (72) the pump (1) at said preset maximum speed, if the calculated speed is higher than the preset maximum speed.

28. The pump according to claim 21, wherein the control device (11) is adapted to:

run (82) the pump (1) at a desired speed level,

determine (84) if the power of the motor (9) is higher than a predetermined reference level of the power of the motor (9), based on the values of the power of the motor (9) obtained by the sensing means (16) for the desired speed level.

29. The pump according to claim 28, wherein the control device (11) is adapted to:

run the pump (1) at the desired speed level, if it is determined that the predetermined condition is not fulfilled, or

run (86) the pump (1) reverse at a predetermined speed for a predetermined period of time, and—

run the pump (1) in its normal operation direction at the desired speed level after said predetermined period of time of reverse operation, if it is determined that the predetermined condition is fulfilled.

30. The pump according to claim 21, wherein the control device (11), at regular intervals during the operation of the pump (1), is adapted to:

run the pump (1) reversely at a predetermined speed for a predetermined period of time, and

run the pump (1) in its normal operation direction at a desired speed level after said predetermined period of time of reverse operation.

31. A pump station comprising a pump (1) according to claim 20, and further comprises an operator unit (22) comprising input means (24) and display means (26), which is adapted to present information related to the operation of the pump (1).