Method for operating a pump unit, pump unit and use thereof

Abstract

A method for operating a pump unit including a pump and a drive motor for the latter, the pump unit being disposed in a fluid circuit that is to be filled with a liquid to be moved and in which the liquid to be moved is moved using the pump unit. In order to provide a method in which the pump unit can be operated in a more energy-efficient manner, it is proposed that the fill status of the fluid circuit be determined and, with the use of a control unit, the working point of the pump unit be modified in operation thereof depending on the fill status of the fluid circuit. Also described is a pump unit for carrying out the method and to the use of a pump unit.

What is claimed is: 
     
         1 . A method for operating a pump unit comprising a pump and a drive motor for the pump, the method comprising:
 moving liquid in a fluid circuit using the pump unit,   determining a fill status of the fluid circuit, and   modifying a working point of the pump unit during operation of the pump unit with a control unit depending on the fill status of the fluid circuit.   
     
     
         2 . The method in accordance with  claim 1 , further comprising determining whether the fluid circuit has not yet been filled or whether the fluid circuit has been filled and moved liquid is circulating. 
     
     
         3 . The method in accordance with  claim 1 , wherein the working point is modified for minimizing a power input of the pump unit when the fluid circuit is in a filled state. 
     
     
         4 . The method in accordance with  claim 1 , wherein an internal control unit of the pump unit is used for determining the fill status of the fluid circuit and for modifying the working point of the pump unit. 
     
     
         5 . The method in accordance with  claim 1 , wherein internal operating parameters of the pump unit are used for determining the fill status. 
     
     
         6 . The method in accordance with  claim 1 , wherein the fill status is determined by determining at least one of a differential pressure of moved liquid applied at the pump and a volumetric flow rate of moved liquid. 
     
     
         7 . The method in accordance with  claim 6 , wherein for determining the differential pressure and/or the volumetric flow rate of moved liquid,
 at least one of a power input of the drive motor, a rotational speed of the drive motor and characteristic values of hydraulic properties of the pump unit are used, with said characteristic values being stored in a storage unit.   
     
     
         8 . The method in accordance with  claim 1 , wherein the working point of the pump unit is modified by changing at least one of a power input and a rotational speed of the drive motor. 
     
     
         9 . The method in accordance with  claim 8 , wherein the power input and/or the rotational speed of the motor are or is controlled depending on at least one of a differential pressure and a volumetric flow rate of moved liquid determined. 
     
     
         10 . The method in accordance with  claim 9 , wherein the working point is not modified when the differential pressure determined differs from a preset or presettable differential pressure by less than a threshold differential pressure and/or when the volumetric flow rate determined differs from a preset or presettable volumetric flow rate by less than a threshold volumetric flow rate. 
     
     
         11 . The method in accordance with  claim 1 , wherein the working point of a circulation mode of operation is set by presetting at least one of a differential pressure and a volumetric flow rate in circulation operation. 
     
     
         12 . The method in accordance with  claim 1 , wherein the determination of the fill status and the modification of the working point are performed in real-time. 
     
     
         13 . The method in accordance with  claim 1 , wherein the method is used in filling fluid circuit of a draindown system of a solar thermal collector appliance with fluid. 
     
     
         14 . A pump unit comprising:
 a pump,   a drive motor for the pump, and   an internal control unit configured to (i) determine a fill status of a fluid circuit in which the pump unit is connected for moving a liquid to be moved, and (ii) modify a working point of the pump unit during operation thereof depending on the fill status of the fluid circuit.   
     
     
         15 . The pump unit in accordance with  claim 14 , the internal control unit is configured to determine whether the fluid circuit has not yet been filled or whether it has been filled and moved liquid is circulating. 
     
     
         16 . The pump unit in accordance with  claim 14 , wherein the working point is modifiable for minimizing a power input of the pump unit when the fluid circuit is in a filled state. 
     
     
         17 . The pump unit in accordance with  claim 14 , wherein internal operating parameters of the pump unit are usable for determining the fill status. 
     
     
         18 . The pump unit in accordance with  claim 14 , wherein the fill status is determinable by at least one of a differential pressure of moved liquid applied at the pump and a volumetric flow rate of the moved liquid. 
     
     
         19 . The pump unit in accordance with  claim 18 , wherein, for determining the differential pressure and/or the volumetric flow rate of moved liquid, at least one of a power input of the drive motor, a rotational speed of the drive motor and characteristic values of hydraulic properties of the pump unit are usable, with said characteristic values being stored in a storage unit. 
     
     
         20 . The pump unit in accordance with  claim 14 , wherein the working point of the pump unit is variable by changing at least one of a power input and a rotational speed of the drive motor. 
     
     
         21 . The pump unit in accordance with  claim 20 , wherein the power input and/or the rotational speed of the drive motor are or is controlled depending on at least one of a differential pressure and a volumetric flow rate of moved liquid. 
     
     
         22 . The pump unit in accordance with  claim 21 , wherein the working point is not modified when a differential pressure differs from a preset or presettable differential pressure by less than a threshold differential pressure and/or when a volumetric flow rate determined differs from a preset or presettable volumetric flow rate by less than a threshold volumetric flow rate. 
     
     
         23 . The pump unit in accordance with  claim 14 , wherein the pump unit comprises a setting element by which the working point of a circulation mode of operation is adjustable by presetting at least one of a differential pressure and a volumetric flow rate in circulation operation. 
     
     
         24 . The pump unit in accordance with  claim 14 , wherein the determination of the fill status and the modification of the working point are performable in real-time. 
     
     
         25 . A method for using of a pump unit comprising a pump and a drive motor for the pump, the method comprising:
 determining a fill status of a fluid circuit in which the pump unit is connected for moving a liquid to be moved,   modifying a working point of the pump unit during operation of the pump unit depending on the fill status of the fluid circuit, and   using the pump unit as a circulation pump unit in a draindown system of a solar thermal collector appliance.