WO2024260636A1

WO2024260636A1 - Pump assembly and method for operating such

Info

Publication number: WO2024260636A1
Application number: PCT/EP2024/063099
Authority: WO
Inventors: Steen Mikkelsen
Original assignee: Grundfos Holdings AS
Current assignee: Grundfos Holdings AS
Priority date: 2023-06-19
Filing date: 2024-05-13
Publication date: 2024-12-26
Anticipated expiration: 2025-12-19

Abstract

The present disclosure is directed to a pump assembly (1) comprising: - a pump housing (3) with a pump housing inlet (7) and a pump housing outlet (9), wherein the pump housing (3) defines an impeller chamber (11) enclosing an impeller (13) for pumping a liquid from the pump housing inlet (7) towards the pump housing outlet (9); - an integrated electric motor drive (5) being mechanically coupled to the impeller (13) via a drive shaft (23, 35), wherein the integrated electric motor drive (5) comprises a stator (43) and a rotor (41), wherein the drive shaft (23, 35) extends along a rotor axis (R) and the rotor (41) is mechanically coupled to the drive shaft (23, 35), wherein the integrated electric motor drive (5) comprises power electronics (45) for controlling an electric current through the stator (43); and - a liquid cooling system for cooling the stator (43) and/or the power electronics (45), wherein the liquid cooling system comprises a closed liquid cooling circuit (57), wherein the closed liquid cooling circuit (57) is filled with a liquid coolant being in direct or indirect thermal contact with the stator (43) and/or the power electronics (45), characterised in that the closed liquid cooling circuit (57) comprises a liquid-to-liquid heat exchanger section, wherein the liquid coolant is guided by the liquid-to-liquid heat exchanger section along a defined coolant flow path in thermal contact with a cold liquid flow for dissipating heat from the liquid coolant to the cold liquid flow.

Description

TECHNICAL FIELD

[01 ] The present disclosure is directed to a pump assembly and a method for operating such. The pump assembly may be a single stage or multistage centrifugal pump, in particular for pumping water or another fluid. The pump assembly is preferably a dry runner centrifugal pump assembly with an integrated electric motor drive.

BACKGROUND

[02] Typically, there is a general interest in designing pumps as compact as possible. Usually, an integrated electric motor drive is often a large or even the largest part of a pump assembly. It is a technical challenge to reduce the size of the integrated electric motor drive without limiting its output power. In particular, cooling of the stator and/or power electronics becomes more challenging the more compact the integrated electric motor drive is designed.

[03] US 6,322,332 Bl describes a device for the external cooling of the electric drive motor of a dry runner centrifugal pump unit. The cooling device of US 6,322,332 Bl , however, increases the outer dimensions of the electric drive motor and only cools the stator, but not power electronics that control an electric current through the stator. US 7,429,809 B2 describes a drive motor for a pump with a cooling by a positively moved liquid coolant. However, the heat dissipation provided by the liquid coolant is not optimal in US 7,429,809 B2. [04] It is therefore an object of the present disclosure to provide a more compact and efficient powerful cooling of the integrated electric motor drive of a pump assembly.

SUMMARY

[05] According to a first aspect of the present disclosure, a pump assembly is provided comprising: a pump housing with a pump housing inlet and a pump housing outlet, wherein the pump housing defines an impeller chamber enclosing an impeller for pumping a liquid from the pump housing inlet towards the pump housing outlet; an integrated electric motor drive being mechanically coupled to the impeller via a drive shaft, wherein the integrated electric motor drive comprises a stator and a rotor, wherein the drive shaft extends along a rotor axis and the rotor is mechanically coupled to the drive shaft, wherein the integrated electric motor drive comprises power electronics for controlling an electric current through the stator; and a liquid cooling system for cooling the statorand/orthe power electronics, wherein the liquid cooling system comprises a closed liquid cooling circuit, wherein the closed liquid cooling circuit is filled with a liquid coolant being in direct or indirect thermal contact with the stator and/or the power electronics, wherein the closed liquid cooling circuit comprises a liquid-to-liquid heat exchanger section, wherein the liquid coolant is guided by the liquid-to- liquid heat exchanger section along a defined coolant flow path in thermal contact with a cold liquid flow for dissipating heat from the liquid coolant to the cold liquid flow.

[06] The “cold liquid flow” may be any liquid that is colder than the liquid coolant when it enters the liquid-to-liquid heat exchanger section. Preferably, the cold liquid flow may be the flow of the liquid that is pumped by the pump assembly, e.g. cold water. It should be noted that “liquid-to-liquid” shall mean herein that heat is transferred from the liquid coolant to the cold liquid flow for dissipating heat, i.e. for cooling purposes.

[07] Tests have shown that the cooling by the liquid cooling system with the liquid-to-liquid heat exchanger section is able to improve the efficiency of the motor drive so significantly that it can be reduced in size significantly compared to an air-cooled motor drive providing the same desired maximum power. The efficiency gain by the liquid cooling system with the liquid-to-liquid heat exchanger section may be up to 50% or more, which allows for significantly smaller motor drive designs, or for a higher maximum power without making the motor drive larger. The motor may, for instance, be a permanent magnet synchronous motor (PMSM) or Permanent Magnet Assisted Synchronous Reluctance (PMASR) motor, or another kind of suitable electric motor.

[08] Optionally, the closed liquid cooling circuit may further comprise a liquid-to-air heat exchanger section, wherein the liquid coolant is guided along the liquid-to-air heat exchanger section for dissipating heat from the liquid coolant to a cooling ambient air flow. Such a liquid- to-air cooling in addition to the liquid-to-liquid cooling further increases the cooling power of the liquid cooling system. It should be noted that “liquid-to-air” shall mean herein that heat is transferred from a liquid to air for dissipating heat, i.e. for cooling purposes.

[09] Optionally, the liquid cooling system comprises a actuatable valve being configured to set a valve position between a first valve position and a second valve position, wherein the liquid coolant is in the first valve position guided along the liquid-to-air heat exchanger section, and wherein the liquid coolant is in the second valve position guided along the liquid-to-liquid heat exchanger section. Such an embodiment is beneficial to selectively operate the liquid cooling system in different cooling modes, i.e. liquid-to-air cooling mode and/or liquid-to-liquid cooling mode, as needed. Preferably, the liquid-to-air cooling mode may be active in both the first valve position and the second valve position, so that the liquid-to-liquid cooling mode comprises in fact both liquid-to-liquid cooling and liquid-to-air cooling. However, it should be noted that the liquid-to-liquid cooling, when activated in the liquid-to- liquid cooling mode, provides the predominant part of the cooling power compared to the liquid-to-air cooling. Preferably, the actuatable valve may not only be actuated to take the first valve position or the second valve position, but also a position in between in order to run the liquid-to-liquid cooling to a desired degree. Thereby, the cooling power of the liquid cooling system may be gradually set by the actuatable valve. It is also advantageous to be able to completely switch off the liquid-to-liquid cooling in order to allow pumping hot liquids that provide little or none cooling capacity in the first place.

[10] An on/off and/or gradual setting of the cooling power is useful, because the maximum cooling power is not always desired in all operating situations. For example, it is beneficial that the integrated electric motordrive warms up after start-up to a desired operating temperature. The lubrification of the bearings, for instance, is optimal in a certain range of operating temperatures. Furthermore, a too high cooling power may lead to undesired condensation at the power electronics or elsewhere. It is thus advantageous to set the cooling power by the actuatable valve. Once the integrated electric motor drive has reached its operating temperature, the liquid cooling system may be operated in the liquid-to-liq- uid cooling mode at maximum cooling power by switching the actuatable valve fully to the second valve position. [1 1 ] Optionally, the pump assembly may further comprise an actuator for actuating the actuatable valve into a desired valve position, wherein the desired valve position is selected from a group comprising: the first valve position, the second valve position, and a valve position between the first valve position and the second valve position. Such an actuator may, for example, be a step motor to bring the actuatable valve into the desired valve position at the first valve position or the second valve position or at a position in between.

[12] Optionally, the pump assembly may further comprise a fan, wherein the fan is arranged to drive the cooling ambient air flow along a heat sink. This is advantageous to avoid condensation and to improve the cooling effect. The liquid coolant has the lowest temperature when it leaves the liquid-to-liquid heat exchanger section. Therefore, it is advisable to guide the liquid coolant on the most direct path into thermal contact with the hot power electronics, i.e. into a section of the closed liquid cooling circuit extending between the stator and the power electronics. Preferably, the heat sink is arranged downstream of such a section of the closed liquid cooling circuit extending between the stator and the power electronics. Thereby, the liquid coolant has absorbed heat from the power electronics that can then be dissipated to the heat sink. Thereby, the cooling effect of the liquid coolant is largest, because the heat sink on the return path reduces the return temperature of the liquid coolant when it is recirculated into the liquid-to-liquid heat exchanger section.

[13] Optionally, the fan may be mechanically coupled to the drive shaft. Preferably, the fan is arranged at an axial side of the integrated electric motor drive that faces toward the pump housing. The fan is preferably arranged to suck in ambient air radially inward into lateral openings of a motor stool that couples the integrated electric motor drive to the pump housing. The fan then preferably blows the ambient cooling air flow towards the heat sink which may preferably be arranged at a lateral side of the integrated electric motor drive.

[14] Optionally, the stator may be arranged axially between the power electronics and the fan. So, the power electronics and the fan are preferably arranged at opposite axial ends of the integrated electric motor drive.

[15] Optionally, the fan is arranged in a fan chamber that has an annular air flow outlet facing axially towards the heat sink. So, the heat sink is arranged downstream of the fan in the axial cooling airflow path.

[16] Optionally, the fan may be a radial fan arranged outside of a motor housing that encloses the stator and the power electronics. The motor housing may define at least a section of the cooling air flow path towards or, preferably, away from the fan.

[17] Optionally, the pump assembly may further comprise a motor stool mechanically connecting the motor housing of the integrated electric motor drive to the pump housing, wherein the fan is circumferenced by the motor stool, wherein the motor stool is preferably made of cast aluminium. Preferably, the motor stool has lateral openings through which the fan can suck in ambient cooling air to be driven along the cooling fins of the heat sink.

[18] Optionally, the motor stool may comprise a lateral air inlet opening through which cooling ambient air is sucked in by the fan, wherein the motor stool comprises inlet airflow cooling ribs extending axially as lattice bars into the lateral air inlet opening. Preferably, the inlet airflow cooling ribs of the motor stool extend over the full axial extension of the lateral air inlet opening. Preferably, the inlet airflow cooling fins of the motor stool ore aligned in axial extension of the cooling fins of the heat sink of the integrated electric motor drive.

[19] Optionally, the liquid cooling system may further comprise a liquid coolant agitator being arranged and configured to circulate the liquid coolant along the closed liquid cooling circuit. Preferably, the liquid coolant agitator is an electrically driven coolant pump or a hub-less propeller wheel being magnetically coupled to the drive shaft. Preferably, the liquid coolant agitator is arranged axially between the stator and the power electronics. Preferably, the liquid coolant absorbs heat from the power electronics upstream of the liquid coolant agitator and dissipates heat to the heat sink downstream of the liquid coolant agitator.

[20] Optionally, the coolant flow path defined by the liquid-to-liquid heat exchanger section of the closed liquid cooling circuit may extend along a spiralling, winding, and/or meandering path through and/or within the pump housing.

[21 ] Optionally, the liquid-to-liquid heat exchanger section of the closed liquid cooling circuit may at least partly be formed by a pump head of the pump housing and/or at least partly by a conduit within the impeller chamber. This allows for a maximum length of coolant flow path with the least negative hydrodynamic influence on the pumped liquid that provides the cold liquid flow.

[22] Optionally, a first heat absorption section of the closed liquid cooling circuit extends between the stator and the power electronics, where the liquid coolant is in thermal contact with the power electronics. Such a first heat absorption section is preferably arranged in direct thermal contact, or mitigated by a thermally conductive paste or pad, with a RGB carrying the power electronics. The RGB preferably extends perpendicular to the rotor axis at the axial end of the motor housing that faces away from the pump housing. The first heat absorption section of the closed liquid cooling circuit preferably extends in radial, preferably inward, direction at an axial position between the stator and the power electronics.

[23] Optionally, a second heat absorption section of the closed liquid cooling circuit, preferably arranged downstream of the first heat absorption section of the closed liquid cooling circuit, may extend along a helical, winding, and/or meandering path around the stator housing. If the liquid coolant has not heated up in the first heat absorption section above the stator temperature, the liquid coolant has still cooling power along the second heat absorption section to absorb radially outward transferred heat coming from the stator. Simultaneously, the liquid coolant may, along the second heat absorption section, dissipate heat radially further outward to the heat sink.

[24] Optionally, the coolant flow path defined by the liquid-to-liquid heat exchanger section of the closed liquid cooling circuit may be at least 10 times longer than its average diameter. This is highly beneficial to achieve a sufficiently high heat transfer along the liquid-to-liquid heat exchanger section.

[25] Optionally, the closed liquid cooling circuit may comprise a liquid- to-air heat exchanger section being formed by a volume between a motor-facing three-dimensional surface structure of a motor stool and a heat-conductive metal sheet defining a wall of a fan chamber that accommodates the fan. Preferably, the fan chamber wall defined by the heat-conductive metal sheet has a bowl-shape with a central opening defining an air suction inlet eye of the fan. At the motor facing side of the fan chamber, a front face of the motor housing that faces towards the pump housing may have a smaller diameter than the heat- conductive metal sheet, such that the fan chamber may have an annular air flow outlet directed away from the pump housing along the heat sink.

[26] Optionally, the fan-facing three-dimensional surface structure of the motor stool may comprise turbulence inducers causing the liquid coolant to flow turbulently along the liquid-to-air heat exchanger section. The volume between the three-dimensional surface structure of a motor stool and the heat-conductive metal sheet may have a shape of a flat ring that bends upward in radially outward direction, wherein a plurality of the turbulence inducers are distributed over the ring-shape in form of support structures that support the heat-conductive metal sheet. The motor stool may further define a coolant inlet of the liquid-to-air heat exchanger section and a coolant outlet of the liquid-to-air heat exchanger section, wherein the three-dimensional surface structure of the motor stool guides the liquid coolant from the coolant inlet through the ring-shaped volume around the rotor axis to the coolant outlet. Preferably, the coolant inlet is arranged at a motor-facing end of the volume, so that any air bubbles may exit the volume through the coolant inlet.

[27] Optionally, the liquid cooling system may comprise a closable filling opening for filling the closed liquid cooling circuit with liquid coolant. Preferably, the filling opening may be defined by the motor stool close to the coolant inlet of the liquid-to-air heat exchanger section. Alternatively, or in addition, the filling opening may be defined by the motor housing at the end of the second heat absorption section of the closed liquid cooling circuit. The liquid cooling system may comprise a coolant flow connection between the motor housing and the motor stool. Preferably, the coolant flow connection is directed in axial direction and arranged radially outward from the fan chamber. [28] Optionally, the liquid cooling system may comprise a pressure compensating reservoir to allow for temperature-related expansions and contractions of the liquid coolant. Furthermore, the pressure compensating reservoir may collect air bubbles within the liquid cooling system. Preferably, the pressure compensating reservoir is arranged a section of the closed liquid cooling circuit furthest away from the pump housing, i.e. most vertically upward in a vertical pump configuration, i.e. when the rotor axis extends vertically. The pressure compensating reservoir may comprise an air-venting valve for exhausting air when the closed liquid cooling circuit is filled with liquid coolant.

[29] Optionally, the liquid-to-liquid heat exchanger section may be arranged outside of the pump housing, wherein cold liquid flow is guided as the cold liquid flow outside of the pumping housing along a conduit line being arranged in thermal contact with the liquid-to-liquid heat exchangersection. Preferably, an inlet of the conduit line may be fluid connected with a high-pressure section of the pump housing. Analogously, it is beneficial if an outlet of the conduit line may be fluid connected with a low-pressure section of the pump housing. Thereby, there is always a cold liquid flow of the pumped liquid through the conduit line when the pump operates.

[30] According to another aspect of the present disclosure, a method is provided for operating a pump assembly as previously described, wherein the liquid cooling system is switched into a liquid-to-liquid cooling mode after a pre-determined period of time after a start-up of the pump assembly has lapsed and/or when a minimum coolant temperature is exceeded, wherein the liquid coolant is, in the liquid-to-liquid cooling mode, guided by the liquid-to-liquid heat exchanger section along the defined coolant flow path in thermal contact with a cold liquid flow for dissipating heat from the liquid coolant to the cold liquid flow. Preferably, the cold liquid flow is provided by the liquid that is pumped by the pump assembly.

[31 ] Optionally, the liquid cooling system may be run in a liquid-to-air cooling mode as long as it is not running in the liquid-to-liquid cooling mode, wherein the liquid coolant is, in the liquid-to-air cooling mode, guided along a liquid-to-air heat exchanger section of the closed liquid cooling circuit, wherein the liquid-to-air heat exchanger section is formed by a volume between a motor-facing three-dimensional surface structure of a motor stool and a heat-conductive metal sheet defining a wall of a fan chamber that accommodates a fan. It should be noted that the liquid coolant may also be guided along the liquid-to-air heat exchanger section in the liquid-to-liquid cooling mode. Thereby, the liquid-to-liquid cooling mode may in fact include both liquid-to-liquid cooling and liquid-to-air cooling. However, the liquid-to-liquid cooling provides the predominant contribution to the cooling power in the liquid-to- liquid cooling mode.

SUMMARY OF THE DRAWINGS

[32] Embodiments of the present disclosure will now be described by way of example with reference to the following figures of which:

Fig. 1 shows a partially cut perspective view of an example of an embodiment of a pump assembly according to the present disclosure;

Fig. 2 shows the pump assembly of Fig.2 from a different perspective; Fig. 3 shows the pump assembly of Figs. 1 and 2 with a longitudinal cut through the integrated electric motor drive;

Fig. 4 shows the pump assembly of Figs. 1 -3 with an indicated coolant flow along a feed section of the closed liquid cooling circuit;

Fig. 5 shows the pump assembly of Figs. 1 -4 with an indicated cooling air flow;

Fig. 6 shows the pump assembly of Figs. 1 -5 with an indicated liquid coolant flow into a liquid-to-air heat exchanger section of the closed liquid cooling circuit;

Fig. 7 shows the pump assembly of Figs. 1 -6 with a actuatable valve of the liquid cooling system in a first valve position to run the liquid cooling system in a liquid-to-air cooling mode;

Fig. 8 shows the pump assembly of Figs. 7 from a different perspective with an indicated liquid coolant flow towards a feed section of the closed liquid cooling circuit;

Fig. 9 shows the pump assembly of Figs. 1 -8 with a actuatable valve of the liquid cooling system in a second valve position to run the liquid cooling system in a liquid-to-liquid cooling mode;

Fig. 10 shows a partial longitudinal cut view of parts of an integrated motor drive and a motor stool of anther embodiment of a pump assembly according to the present disclosure; and Fig. 1 1 shows a motor housing part of the pump assembly of Fig.

10.

DETAILED DESCRIPTION

[33] Figs. 1 -9 show a first embodiment of a two-stage vertical dry runner centrifugal pump assembly 1 comprising a pump housing 3 and an integrated electric motor drive 5 comprising a permanent magnet synchronous motor (PMSM). The pump assembly 1 is configured to be installed at a liquid pipe (not shown) in order to drive a flow of a liquid, e.g., water, from a pump housing inlet 7 towards a pump housing outlet 9. The pump housing inlet 7 and the pump housing outlet 9 are arranged coaxially to each other at opposite sides of the pump housing 3. Thereby, the pump assembly 1 can be installed at a straight section of a liquid pipe. The pump housing inlet 7 and the pump housing outlet 9 each comprise a connection flange for fluid-tight connection with a liquid pipe. The pump housing 3 further defines an impeller chamber 1 1 enclosing two stages of impellers 13 that are rotatable about a rotor axis R within the impeller chamber 1 1 . The pump housing 3 further defines a suction path 15 guiding the liquid from the pump housing inlet 7 towards a suction mouth 17 of the impeller 13. The pump housing 3 further defines a pressure path 19 guiding the liquid that radially exits the impeller 13 along a volute path towards the pump housing outlet 9.

[34] In order to facilitate the description of the arrangement of the components of the pump assembly 1 relative to each other, Fig. 1 shows a right-handed Cartesian coordinate system, of which the z-axis is arbitrarily chosen to extend along the rotor axis R. The x-axis is arbitrarily chosen to be the coaxial axis of the pump housing inlet 7 and the pump housing outlet 9 pointing from the pump housing inlet 7 towards the pump housing 9. The y-axis is a lateral axis perpendicular to a xz-plane spanned by the x-axis and the z-axis. Preferably, the pump assembly 1 is a vertical pump, i.e., the rotor axis R is the vertical axis z. Thus, the z-axis points vertically upward. The x-axis and the y-axis span a horizontal xy- plane. It should be noted that the pump assembly 1 may be installed in any spatial orientation; Fig. 1 merely shows a preferred embodiment with a vertical rotor axis R. Therefore, spatial terms like “upper”, “lower”, “above”, and “below” etc. refer to an embodiment with a z-axis pointing vertically upward. The terms “axial”, “lateral” shall refer to the rotor axis R if not specified otherwise.

[35] The pump housing 3 comprises an upper opening 21 for inserting the impellers 13 when the pump is assembled. The impellers 13 are mechanically coupled to a drive shaft 23 extending along the rotor axis R vertically upward out of the impeller chamber 1 1 . The upper opening 21 of the impeller chamber 1 1 is sealingly closed by a pump head 25. The pump head 25 acts as a carrier for a shaft seal element 26 that functions as a shaft seal for the drive shaft 23 protruding out of the impeller chamber 1 1 .

[36] The integrated electric motor drive 5 is releasably mechanically coupled to the pump housing 3 by means of a motor stool 27. In the embodiment shown (see Fig. 3), the pump head 25 is an integral part of the motor stool 27 and/or formed by it. Alternatively, the pump head 25 and the motor stool 27 may be separate parts. The motor stool 27 defines an upper mounting flange 29 (see Fig. 9) for releasably mounting the integrated electric motor drive 5 thereon. The motor stool 27 has lateral access openings 31 (see Fig. 3). The access openings 31 allows access to fixing screws of the shaft seal element 26, to have free sight to inspect the shaft seal element 26 and to see the drive shaft 23 rotation. The openings 31 are closed for pump operation by removable cover plates 32 in order to force ambient cooling air to be sucked in through inlet airflow cooling ribs 34 (see Fig. 4) of the motor stool 27. The last point will be explained in more detail below with reference to Fig. 4. [37] It should be noted that the drive shaft 23 has two coaxially arranged sections that are releasably coupled to each other to transfer torque: a lower pump drive shaft 33 and an upper motor drive shaft 35. The pump drive shaft 33 extends from the pump housing 3 towards the integrated electric motor drive 5. The motor drive shaft 35 extends within the integrated electric motor drive 5 and may or may not protrude at a lower axial end of the integrated electric motor drive 5. There is a releasable shaft coupling 37 between the pump drive shaft 33 and the motor drive shaft 35.

[38] The integrated electric motor drive 5 comprises rotatable parts and static parts. The rotatable parts comprise the motor drive shaft 35 and a rotor 41. The motor drive shaft 35 extends along the rotor axis R and the rotor 41 is mechanically coupled to the motor drive shaft 35. The static parts comprise a stator 43 and power electronics 45 for controlling an electric current through the stator 43. The stator 43 surrounds the rotor 41. The stator 43 is enclosed by a stator housing 47, which preferably comprises a thermally conductive material, e.g., aluminium. The power electronics 45 are arranged on a first printed circuit board (PCB) 49 (see Fig. 3) extending essentially perpendicular to the rotor axis R, i.e., in a horizontal xy-plane, in an upper axial end portion of the integrated electric motor drive 5. Further power electronics 50 are arra nged on a second printed circuit board (PCB) 52 extending essentially parallel to the rotor axis R, i.e., in a verticalzy-plane, at a lateral side of the integrated electric motor drive 5. The integrated electric motor drive 5 further comprises a motor housing 51 and two electronics housings 54a, b, wherein the motor housing 51 encloses the stator housing 47 with the stator 43, the first electronics housing 54a encloses the first PCB 49, and the second electronics housing 54b encloses the second PCB 52. An upper opening 53 of the motor housing 51 is closed by a motor housing lid 55 (see Fig. 2). The motor housing 51 and/or the motor housing lid 55 are preferably made of a thermally conductive material, e.g., a metal, such as cast iron. The motor housing lid 55 defines a thermally conductive bottom of the first electronics housing 54a and/or the second electronics housing 54b, wherein the power electronics 45, 50 within the first electronics housing 54a and/or the second electronics housing 54b are arranged in direct or indirect thermal contact with the motor housing lid 55. A thermally conductive paste and/or pad may be used facilitate the thermal contact.

[39] The first electronics housing 54a and/or the second electronics housing 54b may be formed as cup-shaped lids made of a polymer and/or composite material, wherein the motor housing lid 55, the first electronics housing 54a and the second electronics housing 54b complement each other to form an L-shaped enclosure for the electronics of the integrated electric motor drive 5.

[40] The integrated electric motor drive 5 further comprises a liquid cooling system comprising a closed liquid cooling circuit 57 (see arrows in Figs. 4 and 6-10) and a liquid coolant agitator 59. The closed liquid cooling circuit 57 is filled with liquid coolant being in direct or indirect thermal contact with the stator 43 and/or the power electronics 45. The term “direct or indirect thermal contact” shall mean herein that there is no air gap or heat insulating material interposed. The term “direct or indirect thermal contact” shall include embodiments with one or more thermally conductive material(s) interposed, e.g., in form of a paste and/or a pad.

[41 ] Fig. 4 shows on the left-hand-side an upwardly (positive z-direc- tion) directed feed section 58 of the closed liquid cooling circuit 57. The liquid coolant is in the feed section 58 colder than anywhere else in the closed liquid cooling circuit 57. The feed section 58 ends into the motor housing lid 55, which is typically heated up by the power electronics 45, 50. Thereby, the cold liquid coolant absorbs heat on its way through the motor housing lid 55. The motor housing lid 55 thus defines a first heat absorption section 89 of the closed liquid cooling circuit 57. A vertical part of the first heat absorption section 89 cools the electronics 50 on the second PCB 52 in the second electronics housing 54b. A horizontal part of the first heat absorption section 89 cools the electronics 45 on the first PCB 49 in the first electronics housing 54a.

[42] As can be seen in Figs. 5-7 and 9, the liquid cooling system further comprises a pressure compensating reservoir 62 connected by a hose or pipe 63 to the closed liquid cooling circuit 57 to allow for thermal expansions and contractions of the liquid coolant. The liquid coolant within the closed liquid cooling circuit 57 is thus able to thermally expand into the pressure compensating reservoir 62. The first heat absorption section 89 exits into a downwardly (negative z-direction) directed coolant outlet 64 that is coaxially arranged to the rotor axis R.

[43] The liquid coolant agitator 59, which is arranged underneath the motor housing lid 55 and coaxially to the rotor axis R, receives the liquid coolant from the coolant outlet 64. The liquid coolant agitator 59 is mounted within the closed liquid cooling circuit 57 to be rotatable about the rotor axis R and it is magnetically driven by one or more of the movable parts, e.g., here the motor drive shaft 35. In the shown embodiment, the liquid coolant agitator 59 is an impeller 66 coupled to a drive pin 68 that extends into a top end pocket of the motor drive shaft 35. The motor drive shaft 35 is equipped with two or more magnets and/or ferromagnetic sections 60, which are circumferentially distributed about the top end pocket of the motor drive shaft 35. The drive pin 68 is connected to corresponding magnets and/or ferromagnetic sections 70 being arranged within magnetic coupling range of the magnets and/or ferromagnetic sections 60 of the motor drive shaft 35. The impeller 66 of the liquid coolant agitator 59 comprises vanes defining fluid channels for driving the coolant flow in radial direction. The liquid coolant agitator 59 is placed within an agitator housing 72 that acts as a bearing for the liquid coolant agitator 59 and as a plug to close a central top opening in the stator housing 47. The agitator housing 72 extends between the magnets and/or ferromagnetic sections 70 of the liquid coolant agitator 59 and the magnets and/or ferromagnetic sections 60 of the motor drive shaft 35, so that the coupling magnetic field extends through the agitator housing 72, Therefore, the agitator housing 72 preferably comprises nonferromagnetic material, e.g., a polymer and/or a composite material.

[44] After the liquid coolant is driven by the liquid coolant agitator 59 to flow radially outward between a top side of the stator housing 47 and the motor housing lid 55, it enters a second heat absorption section 91 of the closed liquid cooling circuit 57. The second heat absorption section 91 extends along a helical, winding, and/or meandering path around the stator housing 47. The stator housing 47 defines a radially inner wall of the second heat absorption section 89 and guiding walls to guide the liquid coolant several times around the stator housing 47. The motor housing 51 defines a radially outer wall of the second heat absorption section 91 and comprises radially outwardly directed and axially extending cooling fins 81 . Thereby, the motor housing 51 defines a heat sink 61 for dissipating heat to ambient air. The liquid coolant absorbs heat from the stator 43 through the stator housing 47 and transfers it to radially outward to the motor housing 51 which is cooled by an ambient air flow (see Fig. 5).

[45] Fig. 5 shows how the integrated electric motor drive 5 is cooled by an ambient cooling air flow. The integrated electric motor drive 5 further comprises a radial fan 79 arranged axially below the motor housing 51 and circumferenced by the motor stool 27. The fan 79 is mechanically coupled to the motor drive shaft 35 in order to rotate therewith. Fig. 5 shows a cooling air flow path indicated by arrows. The cooling air flow is driven by the fan 79 sucking ambient air in through the motor stool 27. The motor stool 27 comprises at least one lateral air inlet opening through which ambient air is sucked in by the fan 79. Furthermore, the motor stool 27 comprises inlet airflow cooling ribs 34 extending axially as lattice bars into the lateral air inlet opening. Thereby, the motor stool 27 acts as a heat dissipating body that is preferably made of cast aluminium. In order to guide the ambient air through the lateral air inlet opening along the inlet airflow cooling ribs 34 rather than the large access openings 31 , the access openings 31 are closed by the removable cover plates 32.

[46] The motor stool 27 forms a bottom part of a fan chamber that accommodates the fan 79. A heat-conductive metal sheet 82 of the motor stool 27 forms a wall of the fan chamber and has a bowl-shape with a central bottom opening defining an air suction inlet eye 87 of the fan 79. At the upper side of the fan chamber, a motor housing bottom 73 forms a ceiling of the fan chamber, wherein the motor housing bottom 73 has a smaller diameterthan the heat-conductive metal sheet 82, such that the fan chamber has an annular air flow outlet 84 directed upward along the cooling fins 81 of the heat sink 61 that is defined by the motor housing 51 .

[47] As can be seen in Fig. 6, the motor stool 27 further defines a liquid- to-air heat exchanger section 82 of the closed liquid cooling circuit 57. The liquid-to-air heat exchanger section 82 is formed by a volume between an upward facing three-dimensional surface structure of the motor stool 27 and the heat-conductive metal sheet 80. The volume has a shape of a flat ring that bends upward in radially outward direction. The liquid-to-air heat exchanger section 82 thereby provides for the liquid coolant to be in thermal contact with a large surface that is cooled by the cooling ambient air flow which is driven by the fan 79. It is cooled from the bottom side by the inlet flow of cooling ambient air and from the top side by the outlet flow of cooling ambient flow with a good heat transport through the preferably thin heat-conductive metal sheet 80. So, the liquid coolant efficiently dissipates heat to the cooling ambient air flow when it flows through the liquid-to-air heat exchanger section 80 of the closed liquid cooling circuit 57.

[48] In order to improve the heat transfer from the liquid coolant to the cooling ambient air, the three-dimensional surface structure of the motor stool 27 comprises turbulence inducers 88 that cause the liquid coolant to flow turbulently along the liquid-to-air heat exchanger section 82. The plurality of turbulence inducers 88 are distributed within the ring-shaped volume in form of support structures that support the heat-conductive metal sheet 80 from below. The motor stool 27 further comprises a coolant inlet 90 of the liquid-to-air heat exchanger section 82 and a coolant outlet 92 of the liquid-to-air heat exchanger section 82, wherein the three-dimensional surface structure of the motor stool guides the liquid coolant from the coolant inlet 90 through the ring-shaped volume around the rotor axis R to the coolant outlet 92. A dividing wall 94 circumferentially arranged between the coolant inlet 90 and the coolant outlet 92 prevents the liquid coolant from taking a direct short-cut. It should be noted that the coolant inlet 90 is arranged at an upper end of the liquid- to-air heat exchanger section 82, so that any air bubbles may exit the ring-shaped volume through the coolant inlet 90.

[49] As shown in Fig. 6, the liquid cooling system further comprises a closable filling opening 96 for filling the closed liquid cooling circuit with liquid coolant, e.g., when the pump is assembled or maintained. There is also a coolant flow connection 98 between the motor housing 51 and the motor stool 27. The coolant flow connection 98 is here directed in axial direction and arranged radially outward from the fan chamber. The liquid coolant thus exits the second heat absorption section 91 via the coolant flow connection 98 into the coolant inlet 90 of the liquid-to-air heat exchanger section 82. [50] Fig. 7 shows how the liquid coolant exits the liquid-to-air heat exchanger section 82 downward at the coolant outlet 92. There is a actuatable valve 100 arranged underneath the coolant outlet 92. The actuatable valve 100 is a three-port valve with a top inlet port 102 and two lateral outlet ports 104a, b. An actuator 106, e.g., a step motor, selectively sets a linear position of a valve body 108 into a first valve position (as shown in Figs. 7 and 8), a second valve position, (as shown in Fig. 9) or a valve position between the first valve position and the second valve position. In the first valve position, a first one 104a of the outlet ports 104a,b is open and a second one 104b of the outlet ports 104a,b is closed. In the second valve position, the first outlet port 104a is closed and the second outlet port 104b is open. The first outlet port 104a guides the liquid coolant directly to the feed section 58 of the closed liquid coolant circuit 57. The liquid coolant agitator 59 circulates the liquid coolant along the closed liquid coolant circuit 57. So, when the actuatable valve 100 is in the first valve position as shown in Figs. 7 and 8, the liquid cooling system is run in a liquid-to-air cooling mode.

[51 ] Fig. 9 shows the actuatable valve being in the second valve position when the second outlet port 104b is open. The valve body 108 closes the first outlet port 104a to prevent the liquid coolant from directly entering the feed section 58 of the closed liquid coolant circuit 57. The second outlet port 104b is connected to a downward channel 1 10 through the pump head 25 that leads into a liquid-to-liquid heat exchanger section 1 12 of the closed liquid coolant circuit 57. The liquid-to-liquid heat exchanger section 1 12 is a conduit spiralling around the rotor axis R at the ceiling of the impeller chamber 1 1 (see Figs. 1 , 2, 4 and 8). The liquid-to- liquid heat exchanger section 1 12 is thereby submersed into the pumped liquid within the impeller chamber 1 1 . As the conduit comprises a heat- conductive material, the liquid coolant is able to dissipate heat very efficiently to the cold liquid flow that is provided by the pumped liquid. So, when the actuatable valve 100 in the second valve position as shown in Fig. 9, the liquid cooling system is run in a liquid-to-liquid cooling mode. It should be noted that the liquid-to-air cooling provided by the liquid-to- air heat exchanger section 82 is not switched off in the liquid-to-liquid cooling mode, but the liquid-to-liquid cooling provided by the liquid-to- liquid heat exchanger section 1 12 provides the predominant cooling power. In the liquid-to-air cooling mode, when the liquid-to-liquid cooling is switched off, the cooling power is significantly reduced compared to the liquid-to-liquid cooling mode. This is beneficial to selectively operate the liquid cooling system in different cooling modes, i.e. liquid-to-air cooling mode and/or liquid-to-liquid cooling mode, as needed. Preferably, the actuatable valve may not only be actuated to take the first valve position or the second valve position, but also a position in between in order to run the liquid-to-liquid cooling to a desired degree. Thereby, the cooling power of the liquid cooling system may be gradually set by the actuatable valve. It is also advantageous to be able to completely switch off the liquid-to-liquid cooling in order to allow pumping hot liquids that provide little or none cooling capacity in the first place.

[52] An on/off and/or gradual setting of the cooling power is useful, because the maximum cooling power is not always desired in all operating situations. For example, it is beneficial that the integrated electric motor drive 5 warms up after start-up to a desired operating temperature. The lubrification of the bearings 71 , for instance, is optimal in a certain range of operating temperatures. Furthermore, a too high cooling power may lead to undesired condensation at the power electronics or elsewhere. It is thus advantageous to set the cooling power by the actuatable valve. Once the integrated electric motor drive has reached its operating temperature, the liquid cooling system may be operated in the liquid-to-liquid cooling mode at maximum cooling power by switching the actuatable valve fully to the second valve position. [53] Figs. 10 and 1 1 shows another embodiment of a pump assembly 1 , wherein the liquid-to-liquid heat exchanger section 1 12 is arranged outside of the pump housing, namely as a liquid coolant lake within the integrated electric motor drive 5. The liquid-to-liquid heat exchanger section 1 12 is here a ring-shaped volume at the bottom of a cup-shaped motor housing 51 . A conduit line 1 14 meanders through the volume and has a lateral inlet 1 16 and a lateral outlet 1 18. A cold liquid flow, e.g. the pumped liquid, may be guided into the inlet 1 16 to flow along the conduit line 1 14. As the conduit line 1 14 comprises thermally conductive material and is submersed into a liquid coolant lake at the bottom of the cup-shaped motor housing 51 , there is a heat transfer from the liquid coolant to the cold liquid flow through the conduit line 1 14. Thereby, the cold liquid flow transports heat through the outlet 1 18 effectively away from the integrated electric motor drive 5.

[54] The liquid coolant has the lowest temperature within the closed liquid coolant circuit 59 when it is in the liquid-to-liquid heat exchanger section 1 12 in form of a liquid coolant lake at the bottom of the cupshaped motor housing 51 . It is sucked upward by the liquid coolant agitator along a vertically extending feed section 58 of the closed liquid coolant circuit 59. In the embodiment of Figs. 10 and 1 1 , the feed section 58 is arranged radially between the stator housing 47 and the motor housing 51 . At the top of the stator housing, the liquid coolant is sucked radially inward into the first heat absorption section 89 that is in direct or indirect thermal contact with power electronics (not shown in Figs. 10 and 1 1 ) arranged above. The liquid coolant is guided to the liquid coolant agitator 59 that drives the liquid coolant radially outward to the second heat absorption section 91 that is spials downward around the stator housing 47 similar to the embodiment of Figs. 1 -9. At the bottom of the stator housing 47, the second heat absorption section 91 of the closed liquid coolant circuit 59 exits into the liquid-to-liquid heat exchanger section 1 12 in form of a liquid coolant lake at the bottom of the cupshaped motor housing 51 .

[55] Where, in the foregoing description, integers orelements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present disclosure, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the disclosure that are described as optional, preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims.

[56] The above embodiments are to be understood as illustrative examples of the disclosure. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. While at least one exemplary embodiment has been shown and described, it should be understood that other modifications, substitutions and alternatives are apparent to one of ordinary skill in the art and may be changed without departing from the scope of the subject matter described herein, and this application is intended to cover any adaptations or variations of the specific embodiments discussed herein.

[57] In addition, "comprising" does not exclude otherelements or steps, and "a" or "one" does not exclude a plural number. Furthermore, characteristics or steps which have been described with reference to one of the above exemplary embodiments may also be used in combination with other characteristics or steps of other exemplary embodiments described above. Method steps may be applied in any order or in parallel or may constitute a part or a more detailed version of another method step. It should be understood that there should be embodied within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of the contribution to the art. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the disclosure, which should be determined from the appended claims and their legal equivalents.

[58] List of reference numerals:

I pump assembly

3 pump housing

5 integrated electric motor drive

7 pump housing inlet

9 pump housing outlet

I I impeller chamber

13 impeller

15 suction path

17 suction mouth

19 pressure path

21 upper opening of pump housing

23 drive shaft

25 pump head

26 shaft seal element

27 motor stool

29 upper mounting flange

31 lateral opening of motor stool

32 cover plates

33 pump drive shaft

34 inlet airflow cooling ribs

35 motor drive shaft

37 shaft coupling

41 rotor 43 stator

45 power electronics

47 stator housing

49 first PCB

50 power electronics

51 motor housing

52 second PCB

53 upper opening of motor housing

54a first electronics housing

54b second electronics housing

55 motor housing lid

57 closed liquid cooling circuit

58 feed section

59 liquid coolant agitator

60 ferromagnetic sections

61 heat sink

62 pressure compensating reservoir

63 hose or pipe

64 coolant outlet

66 impeller

68 drive pin

70 ferromagnetic sections

71 bearings

72 agitator housing

73 motor housing bottom

79 fan

80 metal sheet

81 cooling fins

82 liquid-to-air heat exchanger section

84 annular air flow outlet

87 suction inlet eye of the fan

88 turbulence inducers 7 / 34

89 first heat absorption section

90 coolant inlet

91 second heat absorption section

92 coolant outlet

94 dividing wall

96 filling opening

98 coolant flow connection

100 actuatable valve

102 top inlet port

104a,b outlet ports

106 actuator

108 valve body

1 10 channel

1 12 liquid-to-liquid heat exchanger section

1 14 conduit line

1 16 inlet

1 18 outlet

R rotor axis z vertical axis x coaxial axis of the pump housing inlet and outlet y horizontal axis

Claims

1. A pump assembly (1 ) comprising: a pump housing (3) with a pump housing inlet (7) and a pump housing outlet (9), wherein the pump housing (3) defines an impeller chamber (1 1 ) enclosing an impeller ( 13) for pumping a liquid from the pump housing inlet (7) towards the pump housing outlet (9); an integrated electric motor drive (5) being mechanically coupled to the impeller (13) via a drive shaft (23, 35), wherein the integrated electric motor drive (5) comprises a stator (43) and a rotor (41 ), wherein the drive shaft (23, 35) extends along a rotor axis (R) and the rotor (41 ) is mechanically coupled to the drive shaft (23, 35), wherein the integrated electric motor drive (5) comprises power electronics (45, 50) for controlling an electric current through the stator (43); and a liquid cooling system for cooling the stator (43) and/or the power electronics (45), wherein the liquid cooling system comprises a closed liquid cooling circuit (57), wherein the closed liquid cooling circuit (57) is filled with a liquid coolant being in direct or indirect thermal contact with the stator (43) and/or the power electronics (45, 50), characterised in that the closed liquid cooling circuit (57) comprises a liquid-to-liquid heat exchanger section (1 12), wherein the liquid coolant is guided by the liquid-to-liquid heat exchanger section (1 12) along a defined coolant flow path in thermal contact with a cold liquid flow for dissipating heat from the liquid coolant to the cold liquid flow.

2. The pump assembly (1 ) according to claim 1 , wherein the closed liquid cooling circuit (57) further comprises a liquid-to-air heat exchangersection (82), wherein the liquid coolant is guided along the liquid-to-air heat exchanger section (82) for dissipating heat from the liquid coolant to a cooling ambient air flow.

3. The pump assembly (1 ) according to claim 2, wherein the liquid cooling system comprises a actuatable valve (100) being configured to set a valve position between a first valve position and a second valve position, wherein the liquid coolant is in the first valve position guided along the liquid-to-liquid heat exchanger section (1 12), and wherein the liquid coolant is in the second valve position guided along the liquid-to-air heat exchanger section (82).

4. The pump assembly ( 1 ) according to claim 3, further comprising an actuator (106) for actuating the actuatable valve (100) into a desired valve position, wherein the desired valve position is selected from a group comprising: the first valve position, the second valve position, and a valve position between the first valve position and the second valve position.

5. The pump assembly ( 1 ) according to any of the claim 2 to 4, further comprising a fan (79), wherein the fan (79) is arranged to drive the cooling ambient air flow along a heat sink (61 ).

6. The pump assembly (1 ) according to claim 5, wherein the fan (79) is mechanically coupled to the drive shaft (23, 35).

7. The pump assembly ( 1 ) according to claims 5 or 6, wherein the stator (43) is arranged axially between the power electronics (45) and the fan (79).

8. The pump assembly (1 ) according to claim 5 to 7, wherein the fan (79) is arranged in a fan chamber that has an annular air flow outlet (84) facing axially towards the heat sink (61 ).

9. The pump assembly (1 ) according to claim 7 or 8, wherein the fan (79) is a radial fan arranged outside of a motor housing (51 ) that encloses the stator (43) and the power electronics (45).

10. The pump assembly ( 1 ) according to any of the claims 5 to 9, further comprising a motor stool (27) mechanically connecting the integrated electric motor drive (5) to the pump housing (3), wherein the fan (79) is circumferenced by the motor stool (27), wherein the motor stool (27) is preferably made of cast aluminium.

1 1. The pump assembly (1 ) according to claim 10, wherein the motor stool (27) comprises a lateral air inlet opening for cooling ambient air to be sucked in through by the fan (79), wherein the motor stool (27) comprises inlet airflow cooling ribs (34) extending axially as lattice bars into the lateral air inlet opening.

12. The pump assembly ( 1 ) according to any of the preceding claims, wherein the liquid cooling system further comprises a liquid coolant agitator (59) being arranged and configured to circulate the liquid coolant along the closed liquid cooling circuit (57).

13. The pump assembly ( 1 ) according to any of the preceding claims, wherein the coolant flow path defined by the liquid-to-liquid heat exchanger section (1 12) of the closed liquid cooling circuit (57) extends along a spiralling, winding, and/or meandering path through and/or within the pump housing (3).

14. The pump assembly ( 1 ) according to any of the preceding claims, wherein the liquid-to-liquid heat exchanger section (1 12) of the closed liquid cooling circuit (57) is formed at least partly by a pump head (25) of the pump housing (3) and/or at least partly by a conduit within the impeller chamber (1 1 ).

15. The pump assembly ( 1 ) according to any of the preceding claims, wherein a first heat absorption section (89) of the closed liquid cooling circuit (57) extends between the stator (43) and the power electronics (45, 50), where the liquid coolant is in thermal contact with the power electronics (45, 50).

16. The pump assembly ( 1 ) according to any of the preceding claims, wherein a second heat absorption section (91 ) of the closed liquid cooling circuit (57) extends along a helical, winding, and/or meandering path around the stator housing (47).

17. The pump assembly ( 1 ) according to any of the preceding claims, wherein the coolant flow path defined by the liquid-to-liquid heat exchanger section (1 12) of the closed liquid cooling circuit (57) is at least 10 times longer than its average diameter.

18. The pump assembly ( 1 ) according to any of the preceding claims, wherein the closed liquid cooling circuit (57) comprises a liquid-to- air heat exchanger section (82) being formed by a volume between a motor-facing three-dimensional surface structure of a motor stool (27) and a heat-conductive metal sheet (80) defining a wall of a fan chamber that accommodates a fan (79).

19. The pump assembly ( 1 ) according to claim 18, wherein the fan-facing three-dimensional surface structure of the motor stool (27) comprises turbulence inducers (88) causing the liquid coolant to flow turbulently along the liquid-to-air heat exchanger section (82).

20. The pump assembly ( 1 ) according to any of the preceding claims, wherein the liquid cooling system comprises a closable filling opening (96) for filling the closed liquid cooling circuit (57) with liquid coolant.

21 . The pump assembly ( 1 ) according to any of the preceding claims, wherein the liquid cooling system comprises a pressure compensating reservoir (62) to allow for temperature-related expansions and contractions of the liquid coolant.

22. The pump assembly ( 1 ) according to any of the preceding claims, wherein the liquid-to-liquid heat exchanger section(1 12) is arranged outside of the pump housing (3), wherein the cold liquid flow is guided outside of the pumping housing (3) along a conduit line (1 14) being arranged in thermal contact with the liquid-to-liquid heat exchanger section (1 12).

23. A method for operating a pump assembly (1 ) according to any of the preceding claims, wherein the liquid cooling system is switched into a liquid-to-liquid cooling mode after a pre-determined period of time after a start-up of the pump assembly ( 1 ) has lapsed and/or when a minimum coolant temperature is exceeded, wherein the liquid coolant is, in the liquid-to-liquid cooling mode, guided by the liquid-to-liquid heat exchanger section (1 12) along the defined coolant flow path in thermal contact with a cold liquid flow for dissipating heat from the liquid coolant to the cold liquid flow.

24. The method of claim 23, wherein the liquid cooling system is run in a liquid-to-air cooling mode as long as it is not running in the liquid- to-liquid cooling mode, wherein the liquid coolant is, in the liquid- to-air cooling mode, guided along a liquid-to-air heat exchanger section (82) of the closed liquid cooling circuit (57), wherein the liquid-to-air heat exchanger section (82) is formed by a volume between a motor-facing three-dimensional surface structure of a motor stool (27) and a heat-conductive metal sheet (80) defining a wall of a fan chamber that accommodates a fan (79).