ENTRAPMENT DETECTION FOR VARIABLE SPEED PUMP SYSTEM USING LOAD COEFFICIENT

• US 20130108479A1
• Filed: 10/30/2012
• Published: 05/02/2013
• Est. Priority Date: 11/01/2011
• Status: Active Grant

• Current Assignee: Regal Beloit America, Inc.
• Original Assignee: Regal Beloit Epc Inc. (Regal Rexnord Corp.)
• Inventors: Branecky, Brian Thomas, Guzelgunler, Yilcan
• Granted Patent: US 9,689,396 B2
• Time in Patent Office: Days
• US Class Current: 417/53
• 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 value indicative of pump performance;

calculate a pump load coefficient based at least in part on the value indicative of pump performance, wherein value of the pump load coefficient value does not change substantially due to changes in pump speed and is indicative of a blockage of a drain in a liquid holding tank, the drain being coupled to an input of the pump;

detect a blockage of the drain based at least in part on the calculated pump load coefficient; and

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

2. The pump monitoring system of claim 1, wherein the value indicative of pump performance includes a value indicative of motor power of the pump.

3. The pump monitoring system of claim 2, wherein the controller is further configured to determine a value indicative of water velocity, and 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 value indicative of water velocity.

4. The pump monitoring system of claim 2, wherein the controller is further configured to determine a value indicative of motor speed of the pump, and wherein the pump load coefficient is calculated based on the equation:

K_k=P/V³

where L_lc is the value indicative of the pump load coefficient, P is the value indicative of the motor power of the pump, and V is the value indicative of motor speed of the pump.

5. 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.

6. 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.

7. The pump monitoring system of claim 6, wherein the value indicative of pump performance includes a value indicative of motor power of the pump,

wherein the controller is further configured to determine a value indicative of water velocity, and

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

8. The pump monitoring system of claim 7, wherein the calibrated constant is experimentally determined from an equality of the pump load coefficients for at least two operating points by

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

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

solving for h_heighteq.

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

10. The pump monitoring system of claim 9, wherein the previously calculated pump load coefficient is not the immediately previously pump load coefficient calculated by the controller.

11. The pump monitoring system of claim 9, wherein the controller is further configured to detect a blockage of the drain by signaling a blockage condition when the difference is less than the threshold for a defined period of time.

12. The pump monitoring system of claim 11, wherein the defined period of time is determined as a defined number of sampling cycles.

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

filtering the pump load coefficient;

comparing the filtered pump load coefficient to a slower filtered floating threshold value; and

signaling a blockage condition when the filtered pump load coefficient is less than the floating threshold value for a defined period of time.

14. 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 defined period of time.

15. 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.

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

17. 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 based at least in part on the value indicative of pump performance, wherein value of the pump load coefficient value does not change substantially due to changes in pump speed and is indicative of a blockage of a drain in a liquid holding tank, the drain being coupled to an input of the pump;

detecting a blockage of the drain based at least in part on the calculated pump load coefficient; and

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

18. The method of claim 17, wherein the value indicative of pump performance includes a value indicative of motor power of the pump.

19. The method of claim 18, further comprising determining a value indicative of water velocity, and 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 value indicative of water velocity.

20. The method of claim 18, further comprising determining a value indicative of motor speed of the pump, and wherein the pump load coefficient is calculated based on the equation:

K_lc=P/V³

where K_k is the value indicative of the pump load coefficient, P is the value indicative of the motor power of the pump, and V is the value indicative of motor speed of the pump.

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

22. The method of claim 17, wherein the value indicative of pump performance includes a value indicative of motor power of the pump, further comprising determining a value indicative of water velocity, and

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 of water velocity and motor speed of the pump, and h_heighteq is a calibrated constant determined for a specific pump system.

23. The method of claim 22, further comprising experimentally determining the calibrated constant from an equality of the pump load coefficients for at least two operating points by

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

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

solving for h_heighteq.

24. The method of claim 17, 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.

25. The method of claim 24, wherein the previously calculated pump load coefficient is not the immediately previously pump load coefficient calculated by the controller.

26. The method of claim 24, further comprising signaling a blockage condition when the difference is less than the threshold for a defined period of time.

27. The method of claim 26, wherein the defined period of time is determined as a defined number of sampling cycles.

28. The method of claim 17, wherein the blockage of the drain is detected by

filtering the pump load coefficient;

comparing the filtered pump load coefficient to a slower filtered floating threshold value; and

signaling a blockage condition when the filtered pump load coefficient is less than the floating threshold value for a defined period of time.

29. The method of claim 17, 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 defined period of time.