Entrapment detection for variable speed pump system using load coefficient

• US 9,689,396 B2
• Filed: 10/30/2012
• Issued: 06/27/2017
• Est. Priority Date: 11/01/2011
• Status: Active Grant

• Current Assignee: Regal Beloit Epc Inc. (Regal Rexnord Corp.)
• Original Assignee: Regal Beloit America, Inc.
• Inventors: Guzelgunler, Yilcan, Branecky, Brian Thomas
• Primary Examiner(s): Lettman, Bryan
• Assistant Examiner(s): Solak, Timothy
• Application Number:
  US13/663,525
• Publication Number:
  US 20130108479A1
• Time in Patent Office: 1,701 Days
• CPC Class Codes: F04B 17/03 driven by electric motors
• CPC Class Codes: F04B 2203/0201 Current
• CPC Class Codes: F04B 2203/0208 Power
• CPC Class Codes: F04B 2203/0209 Rotational speed
• CPC Class Codes: F04B 2203/0401 Current
• CPC Class Codes: F04B 2203/0408 Power
• CPC Class Codes: F04B 2203/0409 Linear speed
• CPC Class Codes: F04B 2205/09 Flow through the pump
• CPC Class Codes: F04B 2207/01 Load in general
• CPC Class Codes: F04B 49/065 and making use of computers
• CPC Class Codes: F04B 49/103 Responsive to speed
• CPC Class Codes: F04B 49/106 Responsive to pumped volume
• CPC Class Codes: F04B 51/00 Testing machines, pumps, or pumping installations
• CPC Class Codes: F04D 15/0077 Safety measures F04D15/02 takes precedence
• CPC Class Codes: F04D 15/0088 Testing machines
• CPC Class Codes: F04D 15/0094 Indicators of rotational movement
• CPC Class Codes: F04D 15/0218 the condition being a liquid level or a lack of liquid supply
• CPC Class Codes: F04D 15/0227 Lack of liquid level being detected using a flow transducer
• CPC Class Codes: F04D 15/0236 Lack of liquid level being detected by analysing the parameters of the electric drive, e.g. current or power consumption

Abstract

Methods and systems for monitoring a variable-speed pump system to detect a blockage condition. A value indicative of pump performance is sensed and a pump load coefficient is calculated. The value of the pump load coefficient does not change substantially due to changes in pump speed and is indicative of a blockage of a drain in a liquid holding tank. A blockage of the drain is detected based at least in part on the calculated pump load coefficient and the operation of the pump is adjusted based on the detected blockage.

Claims

1. A pump monitoring system, comprising a controller configured to:

determine a first value for motor power, the first value for motor power indicative of pump performance;

determine a second value, the second value indicative of at least one selected from the group consisting of a liquid velocity and a motor speed;

calculate a pump load coefficient to produce a calculated pump load coefficient, the calculated pump load coefficient based at least in part on the first value and the second value;

filter the calculated pump load coefficient using a first time constant to produce a filtered pump load coefficient;

filter the calculated pump load coefficient using a second time constant to produce a filtered floating threshold value, the second time constant being greater than the first time constant;

compare the filtered pump load coefficient with the filtered floating threshold value;

detect a blockage of a drain based on a comparison of the filtered pump load coefficient and the filtered floating threshold value;

adjust an operation of the pump based on the detected blockage, and

wherein the controller is further configured to

calculate a difference between the calculated pump load coefficient for a first cycle and a previous pump load coefficient calculated for a previous cycle a first defined number of cycles before the first cycle, the first defined number of cycles being greater than one, and

detect a blockage of the drain when the difference traverses a threshold for a second defined number of cycles.

2. The pump monitoring system of claim 1, wherein the pump load coefficient is calculated based on the equation:

K_lc=P/V³

where K_lc is the pump load coefficient, P is the first value indicative of the motor power of the pump, and V is the second value indicative of liquid velocity.

3. The pump monitoring system of claim 1, wherein the value of the pump load coefficient is calculated based at least in part on a head pressure of the pump system.

4. The pump monitoring system of claim 1, wherein the controller is calibrated for a specific pump system to account for the head pressure of the pump system.

5. The pump monitoring system of claim 4,

wherein the controller is configured to calculate the pump load coefficient based on the equation:

6. The pump monitoring system of claim 5, wherein the calibrated constant is experimentally determined from an equality of the pump load coefficients for at least two operating points by

determining a third value indicative of motor power for the specific pump system at a first water speed,

determining a fourth value indicative of motor power for the specific pump system at a second liquid speed, and

solving for h_heighteq.

7. The pump monitoring system of claim 1, wherein the controller is further configured to detect a blockage of the drain by

determining a difference between the calculated pump load coefficient and a previously calculated pump load coefficient;

and

comparing the difference to a threshold.

8. The pump monitoring system of claim 7, wherein the previously calculated pump load coefficient is not the immediately previously pump load coefficient calculated by the controller.

9. The pump monitoring system of claim 1, wherein the controller is further configured to

determine a current of the motor;

determine a speed of the motor;

determine, based on a look up table stored in a memory, an expected current corresponding to the determined speed; and

detect a blockage of the drain when the current of the motor is less than the expected current corresponding to the determined speed for a second defined number of cycles.

10. The pump monitoring system of claim 1, wherein the controller includes a processor and a memory, the memory storing instructions that, when executed by the processor, cause the processor to detect a blockage of the drain.

11. The pump monitoring system of claim 1, wherein the liquid holding tank includes a swimming pool.

12. The pump monitoring system of claim 1, wherein, the second defined number of cycles is less than or equal to the first defined number of cycles.

13. A method of monitoring a pump for a blockage condition, the method comprising:

determining a value indicative of pump performance;

calculating a pump load coefficient for a first cycle to produce a first calculated pump load coefficient, the calculated pump load coefficient based at least in part on the value indicative of pump performance, wherein a value of the pump load coefficient is calculated based on a ratio of motor power to water velocity and is indicative of a blockage of a drain in a liquid holding tank, the drain being coupled to an input of the pump;

calculating a difference between the first calculated pump load coefficient and a previous pump load coefficient calculated for a previous cycle a first defined number of cycles before the first cycle, the first defined number of cycles being greater than one; and

detecting a blockage of the drain when the difference is less than a threshold for a second defined number of cycles, the threshold being less than or equal to zero; and

adjusting an operation of the pump based on the detected blockage.

14. The method of claim 13, wherein the second defined number of cycles is less than or equal to the first defined number of cycles.

15. A method of monitoring a pump for a blockage condition, the method comprising:

determining a first value for motor power, the first value indicative of pump performance;

determining a second value, the second value indicative of at least one selected from the group consisting of a liquid velocity and a motor speed;

calculating a pump load coefficient to produce a calculated pump load coefficient, the calculated pump load coefficient based at least in part on the first value and the second value;

filtering the calculated pump load coefficient using a first time constant to produce a filtered pump load coefficient;

filtering the calculated pump load coefficient using a second time constant to produce a filtered floating threshold value, the second time constant being greater than the first time constant;

comparing the filtered pump load coefficient with the filtered floating threshold value;

detecting a blockage of a drain based on a comparison of the filtered pump load coefficient and the filtered floating threshold value;

calculating a difference between the calculated pump load coefficient for a first cycle and a previous pump load coefficient calculated for a previous cycle a first defined number of cycles before the first cycle, the first defined number of cycles being greater than one; and

detecting a blockage of the drain when the difference traverses a threshold for a second defined number of cycles, the threshold being less than or equal to zero; and

adjusting an operation of the pump based on the detected blockage.

16. The method of claim 15, wherein the pump load coefficient is calculated based on the equation:

K_lc=P/V³

where K_lc is the pump load coefficient, P is the value indicative of the motor power of the pump, and V is the second value indicative of liquid velocity.

17. The method of claim 15, wherein the value of the pump load coefficient is calculated based at least in part on a head pressure of the pump system.

18. The method of claim 15, wherein the pump load coefficient is calculated based on the equation:

K_lc=(P−

h_heighteq*V)/V³

where K_lc is the pump load coefficient, P is the value indicative of the motor power of the pump, V is the value indicative of at least one selected from the group consisting of liquid velocity and motor speed of the pump, and h_heighteq is a calibrated constant determined for a specific pump system.

19. The method of claim 18, further comprising experimentally determining the calibrated constant from an equality of the pump load coefficients for at least two operating points by

determining a third value indicative of motor power for the specific pump system at a first water velocity,

determining a fourth value indicative of motor power for the specific pump system at a second liquid velocity, and

solving for h_heighteq.

20. The method of claim 15, wherein the blockage of the drain is determined by

determining a difference between the calculated pump load coefficient and a previously calculated pump load coefficient;

and

comparing the difference to a threshold.

21. The method of claim 20, wherein the previously calculated pump load coefficient is not the immediately previously pump load coefficient calculated by the controller.

22. The method of claim 15, further comprising

determining a current of the motor;

determining a speed of the motor;

determining, based on a look up table stored in a memory, an expected current corresponding to the determined speed; and

detecting a blockage of the drain when the current of the motor is less than the expected current corresponding to the determined speed for a second defined number of cycles.

23. The method of claim 15, wherein the second defined number of cycles is less than or equal to the first defined number of cycles.