Control system for a pump

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.

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 ).