Motor pump, pump unit

Abstract

A motor pump and pump unit with a compact structure are provided. [Solution] The present invention relates to a motor pump and a pump unit. The pump unit comprises a plurality of motor pumps (MP) and a control device (100). Each of the plurality of motor pumps (MP) comprises an impeller (1), a rotor (2), a stator (3), and a bearing (5) that supports the impeller (1) and is located outside the flow path of the impeller (1). The rotor (2) and the bearing (5) are located in the suction side region (Ra) of the impeller (1).

Description

Technical Field

[0001] The present invention relates to a motor pump, a pump unit, and a method for balancing an impeller of a motor pump.

Background Art

[0002] A pump device including a motor and a pump connected by a coupling is known. Such a pump device has a structure that transmits the driving force of the motor to the impeller of the pump via the coupling.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in such a pump device, since the pump and the motor are arranged side by side, the installation area becomes large. On the other hand, in recent years, the demand for compactification (and energy saving) has been increasing, and as a result, the demand for an integrated structure of the pump and the motor has also been increasing.

[0005] Therefore, an object of the present invention is to provide a motor pump and a pump unit having a compact structure.

[0006] One reference example aims to provide a method for balancing an impeller of a motor pump having a compact structure.

[0007] By connecting multiple motor pumps with a compact structure, the pump unit can be operated without increasing the installation area. However, in order to operate multiple motor pumps stably, it is necessary to monitor the status of these multiple motor pumps and control their operation according to the operating conditions.

[0008] Therefore, one example aims to provide a pump unit that can monitor the status of multiple motor pumps and control the operation of multiple motor pumps. [Means for solving the problem]

[0009] In one embodiment, a motor pump is provided comprising an impeller, a rotor fixed to the impeller, a stator positioned radially outward from the rotor, and a bearing supporting the impeller. The rotor and the bearing are positioned in the suction-side region of the impeller.

[0010] In one embodiment, the motor pump includes a return vane positioned on the rear side of the impeller. In one embodiment, the motor pump is equipped with a thrust load reduction structure provided on the back of the impeller. In one embodiment, the thrust load reduction structure comprises a plurality of back vanes attached to the back of the impeller.

[0011] In one embodiment, the thrust load reduction structure is a plurality of notch structures extending toward the center of the impeller. In one embodiment, the bearing is a sliding bearing comprising a rotating bearing body mounted on the impeller and a stationary bearing body positioned on the suction side of the rotating bearing body. In one embodiment, at least one of the impeller and the bearing is made of a lightweight material.

[0012] In one embodiment, the impeller is a centrifugal impeller having a suction portion formed in the central part and side plates arranged opposite to the main plate, the side plates having an annular projection that extends from the outer edge of the side plate toward the suction portion and to which the rotor is fixed. In one embodiment, the motor pump includes a suction casing located on the suction side of the impeller, and the suction side region is the region between the suction casing and the impeller.

[0013] In one embodiment, a pump unit is provided that includes a plurality of motor pumps and an inverter that controls the operation of each of the plurality of motor pumps.

[0014] In one embodiment, the multiple motor pumps are arranged in series. In one embodiment, the multiple motor pumps are arranged in parallel.

[0015] In one embodiment, a method for adjusting the balance of the impeller of the motor pump is provided. The balancing method includes the steps of forming a through hole in the center of the impeller, inserting a balancing jig into the through hole and rotating the impeller together with the balancing jig, and determining the center of gravity of the impeller while it is rotating and adjusting the center of gravity.

[0016] In one embodiment, the balance adjustment method includes the step of withdrawing the balance adjustment jig and then inserting the center cap into the through hole.

[0017] In one embodiment, a method for adjusting the balance of the impeller of the motor pump is provided. The balancing method includes the steps of inserting a balancing jig into a rotating bearing body mounted on the impeller and rotating the impeller together with the balancing jig, and determining the center of gravity of the impeller while it is rotating and adjusting the center of gravity.

[0018] In one aspect, a method for balancing the impeller of the motor pump is provided. The balance adjustment method includes a step of forming a plurality of weight insertion holes along the circumferential direction of the rotor, a step of determining the center of gravity position of the impeller, and a step of inserting a weight into at least one of the plurality of weight insertion holes to adjust the center of gravity position.

[0019] In one aspect, a method for balancing the impeller of the motor pump is provided. The balance adjustment method includes a step of determining the center of gravity position of the impeller and a step of removing an excess weight that causes a deviation in the center of gravity position of the impeller.

[0020] In one aspect, a pump unit is provided that includes a plurality of motor pumps and a control device that variably operates the plurality of motor pumps. Each of the plurality of motor pumps includes an impeller, a rotor fixed to the impeller, a stator disposed radially outside the rotor, and a bearing that supports the impeller, and the rotor and the bearing are disposed in the suction side region of the impeller.

[0021] In one aspect, the plurality of motor pumps are connected in series, and the control device calculates a lower limit current value based on an assumed current value assumed during normal operation of the motor pump, compares the measured current value during the current operation of the motor pump with the lower limit current value, and determines that an abnormality has occurred in at least one of the plurality of motor pumps when the measured current value is lower than the lower limit current value. In one aspect, the measured current value corresponds to the starting current value when the motor pump starts. In one aspect, the measured current value corresponds to the operating current value during steady operation of the motor pump.

[0022] In one aspect, the control device determines the assumed current value based on at least one of the rated current value and the allowable current value of the motor pump. In one aspect, the control device determines the assumed current value based on the flow rate on the discharge side of the motor pump. In one aspect, the control device determines the assumed current value based on the pressure on the discharge side of the motor pump.

[0023] In one aspect, the lower limit current value is determined based on the number of the plurality of motor pumps. In one aspect, the plurality of motor pumps are connected in parallel, and the control device is configured to shift the start timing of each of the plurality of motor pumps. In one aspect, after starting one motor pump among the plurality of motor pumps, the control device starts a motor pump adjacent to the started motor pump.

[0024] In one aspect, a pump unit is provided that includes the plurality of motor pumps and a plurality of inverters that control the operations of the plurality of motor pumps. Each of the plurality of inverters controls the operation of each of the plurality of motor pumps. <(

[0025] In one aspect, a motor pump is provided that includes an impeller, a rotor fixed to the impeller, a stator disposed radially outside the rotor, and a bearing that supports the impeller. The rotor and the bearing are disposed in the suction side region of the impeller. The impeller is a centrifugal impeller having a suction portion formed in a central portion and side plates disposed opposite to a main plate. The side plates have an annular protrusion portion where the rotor is fixed and disposed radially inside the outer edge portion of the side plates.

[0026] In one aspect, the motor pump includes a cover that covers an exposed portion of the stator.

[0027] In one embodiment, a motor pump is provided comprising an impeller, a rotor fixed to the impeller, a stator positioned radially outward from the rotor, and a bearing supporting the impeller. The rotor and the bearing are positioned in the suction-side region of the impeller, the impeller is a centrifugal impeller having a suction portion formed in its central part and side plates positioned opposite a main plate, and the rotor is fixed to the side plates such as to obstruct the flow path of the impeller formed between the main plate and the side plates.

[0028] In one embodiment, a motor pump is provided comprising a first impeller, a rotor fixed to the first impeller, a stator positioned radially outward from the rotor, a bearing supporting the first impeller, a communication shaft connected to the first impeller, and a second impeller connected to the communication shaft. The rotor and the bearing are positioned in the suction-side region of the first impeller.

[0029] In one embodiment, the motor pump includes an intermediate casing positioned between the first impeller and the second impeller. In one embodiment, the motor pump is equipped with a discharge-side bearing that rotatably supports the communication shaft and is located on the discharge side of the second impeller. In one embodiment, the motor pump comprises a plurality of impellers, including at least the first impeller and the second impeller.

[0030] In one embodiment, a motor pump is provided comprising: a plurality of impellers of different sizes; a plurality of rotors fixed to the plurality of impellers and having different lengths; a plurality of stators having lengths corresponding to the lengths of the plurality of rotors; a plurality of stator casings housing the plurality of stators and having lengths corresponding to the lengths of the plurality of stators; and bearings supporting each of the plurality of impellers. Each of the plurality of rotors and the bearings are located in the suction-side region of each of the plurality of impellers.

[0031] In one embodiment, the plurality of impellers comprises a plurality of side plates having the same diameter and a plurality of main plates having different diameters.

[0032] In one embodiment, a motor pump is provided comprising an impeller, a rotor fixed to the impeller, a stator positioned radially outward from the rotor, a bearing supporting the impeller, and a swivel stopper positioned on the rear side of the impeller. The rotor and the bearing are positioned in the suction-side region of the impeller.

[0033] In one embodiment, a motor pump is provided comprising an impeller, a rotor fixed to the impeller, a stator positioned radially outward from the rotor, a bearing supporting the impeller, and a suction casing and a discharge casing positioned adjacent to the impeller. The rotor and the bearing are positioned in the suction-side region of the impeller, and the suction casing and the discharge casing have a flat flange shape.

[0034] In one embodiment, the motor pump is provided with through bolts for fastening the suction casing and the discharge casing together, and at least one of the suction casing and the discharge casing has a bolt housing for housing the head of the through bolt.

[0035] In one embodiment, a pump unit comprising the above-mentioned plurality of motor pumps is provided. The plurality of motor pumps are connected in series, and the suction casings and discharge casings, which are arranged adjacent to each other, are in surface contact with each other. [Effects of the Invention]

[0036] The rotor and bearings are located in the suction-side region of the impeller. Therefore, the motor pump can make effective use of dead space and, as a result, have a compact structure. [Brief explanation of the drawing]

[0037] [Figure 1] This figure shows one embodiment of a motor pump. [Figure 2] This diagram shows the flow of the handling fluid through the gap between the rotating bearing body and the stationary bearing body. [Figure 3] This figure shows one embodiment of multiple grooves formed in the flange portion of the fixed bearing body. [Figure 4A] Figure 4A shows one embodiment of multiple grooves formed in the cylindrical portion of the fixed bearing body. [Figure 4B] Figure 4B shows another embodiment of the groove formed in the cylindrical portion of the fixed bearing body. [Figure 4C] Figure 4C shows another embodiment of the groove formed in the cylindrical portion of the stationary bearing body. [Figure 5A] Figure 5A shows one embodiment of a thrust load reduction structure provided on the back of an impeller. [Figure 5B] Figure 5B is a view of Figure 5A from the direction of arrow A. [Figure 6] This figure shows another embodiment of the thrust load reduction structure. [Figure 7A] Figure 7A shows a rotor positioned offset from the stator. [Figure 7B] Figure 7B shows a rotor positioned offset from the stator. [Figure 8] This figure shows one embodiment of a bearing having a tapered structure. [Figure 9] This figure shows another embodiment of a bearing having a tapered structure. [Figure 10] This diagram shows a pump unit equipped with multiple motor pumps. [Figure 11] This figure shows another embodiment of the pump unit. [Figure 12] This figure shows another embodiment of the pump unit. [Figure 13A] Figure 13A shows a motor pump as an example. [Figure 13B] Figure 13B shows another embodiment of the motor pump. [Figure 13C] Figure 13C shows another embodiment of the motor pump. [Figure 14] This figure shows one embodiment of a balance adjustment method. [Figure 15] This figure shows one embodiment of a balance adjustment method. [Figure 16] This figure shows one embodiment of a balance adjustment method. [Figure 17] This figure shows one embodiment of a balance adjustment method. [Figure 18] This figure shows one embodiment of a balance adjustment method. [Figure 19] This figure shows another embodiment of the balance adjustment jig. [Figure 20] This figure shows another embodiment of the balance adjustment method. [Figure 21A] Figure 21A is a perspective view showing another embodiment of the pump unit. [Figure 21B] Figure 21B is a plan view of the pump unit shown in Figure 21A. [Figure 22] This diagram shows the control flow of the motor pump by the control device. [Figure 23] This is a diagram showing another embodiment of the impeller. [Figure 24] This is a diagram showing another embodiment of the impeller. [Figure 25] This diagram shows a sealing member positioned between the cover and the side panel. [Figure 26] This is a diagram showing another embodiment of the impeller. [Figure 27] This figure shows another embodiment of the motor pump. [Figure 28] This figure shows another embodiment of the motor pump. [Figure 29] This figure shows another embodiment of the motor pump. [Figure 30] This diagram shows a motor pump with various components that can be selected depending on the operating conditions. [Figure 31A] Figure 31A is a cross-sectional view of a motor pump according to another embodiment. [Figure 31B] Figure 31B shows the motor pump shown in Figure 31A as viewed from the axial direction. [Figure 32A] Figure 32A is a cross-sectional view of a motor pump according to another embodiment. [Figure 32B] Figure 32B is a front view of the suction casing of the motor pump shown in Figure 32A. [Figure 33] This diagram shows a pump unit equipped with a motor pump connected in series. [Figure 34] This is a diagram showing another embodiment of the impeller. [Figure 35] This figure shows another embodiment of the motor pump. [Figure 36] This figure shows a side plate provided on the motor pump according to the embodiment described above. [Figure 37] This is another embodiment of the side plate. [Modes for carrying out the invention]

[0038] The following describes embodiments of the motor pump with reference to the drawings. In the following embodiments, the same or corresponding components are denoted by the same reference numerals, and redundant descriptions are omitted.

[0039] Figure 1 shows one embodiment of a motor pump. As shown in Figure 1, the motor pump MP comprises an impeller 1, an annular rotor 2 fixed to the impeller 1, a stator 3 positioned radially outward from the rotor 2, and a bearing 5 supporting the impeller 1.

[0040] In the embodiment shown in Figure 1, the motor pump MP is a rotating machine equipped with a permanent magnet motor, but the type of motor pump MP is not limited to this embodiment. In one embodiment, the motor pump MP may be equipped with an induction motor or a reluctance motor. When the motor pump MP is equipped with a permanent magnet motor, the rotor 2 is a permanent magnet. When the motor pump MP is equipped with an induction motor, the rotor 2 is a squirrel-cage rotor.

[0041] In the embodiment shown in Figure 1, the impeller 1 is a centrifugal impeller. More specifically, the impeller 1 comprises a disc-shaped main plate 10, side plates 11 positioned opposite the main plate 10, and a plurality of blades 12 positioned between the main plate 10 and the side plates 11. A motor pump MP equipped with the centrifugal impeller 1 has superior lifting characteristics compared to pumps such as axial flow pumps and mixed flow pumps, and can generate high pressure. Furthermore, the motor pump MP in this embodiment can contribute to the rotational stability of the impeller 1 by utilizing the pressure difference generated inside it.

[0042] The side plate 11 comprises a suction section 15 formed in its central part and a main body section 16 connected to the suction section 15. The suction section 15 extends in the direction of the centerline CL of the motor pump MP, and the main body section 16 extends in a direction inclined with respect to the centerline CL (more specifically, perpendicular). The centerline CL is parallel to the flow direction of the liquid (handled liquid) that flows due to the operation of the motor pump MP.

[0043] As shown in Figure 1, the side plate 11 is provided with an annular projection 17 extending from the outer edge 11a of the side plate 11 (more specifically, the end of the main body 16) toward the suction portion 15. In the embodiment shown in Figure 1, the main body 16 and the projection 17 are integrally constructed, but the projection 17 may be a separate component from the main body 16.

[0044] The rotor 2 has an inner diameter larger than the outer diameter of the projection 17 and is fixed to the outer circumferential surface 17a of the projection 17. The stator 3 is arranged to surround the rotor 2 and is housed in the stator casing 20. The stator casing 20 is located radially outward from the impeller 1.

[0045] The motor pump MP comprises a suction casing 21 and a discharge casing 22 located on either side of the stator casing 20. The suction casing 21 is located on the suction side of the impeller 1, and the discharge casing 22 is located on the discharge side of the impeller 1. The impeller 1, rotor 2, and bearing 5 are located radially inward of the stator casing 20 and are positioned between the suction casing 21 and the discharge casing 22.

[0046] The suction casing 21 has a suction port 21a in its central part. The discharge casing 22 has a discharge port 22a in its central part. These suction ports 21a and discharge ports 22a are arranged in a straight line along the center line CL. Therefore, the liquid being handled, which is drawn in from the suction port 21a and discharged from the discharge port 22a, flows in a straight line.

[0047] As shown in Figure 1, the worker inserts the through bolts 25 into the suction casing 21 and the discharge casing 22 with the stator casing 20 sandwiched between them, and then fastens the through bolts 25. In this way, the motor pump MP is assembled.

[0048] When the motor pump MP is operated, the fluid being handled is drawn in through the suction port 21a of the suction casing 21 (see the black arrow in Figure 1). The impeller 1 pressurizes the fluid being handled by its rotation, and the fluid flows inside the impeller 1 perpendicular to the centerline CL (i.e., centrifugal direction). The fluid being handled that is discharged outside the impeller 1 collides with the inner circumferential surface 20a of the stator casing 20, and its direction is reversed. The fluid being handled then passes through the gap between the back of the impeller 1 (more specifically, the main plate 10) and the discharge casing 22 and is discharged from the discharge port 22a.

[0049] As shown in Figure 1, the motor pump MP is equipped with return vanes 30 positioned on the rear side of the impeller 1. In the embodiment shown in Figure 1, a plurality of spirally extending return vanes 30 are provided. These plurality of return vanes 30 are fixed to the discharge casing 22 and face the main plate 10 of the impeller 1. By providing the return vanes 30, the handling fluid discharged from the impeller 1 is smoothly guided to the discharge port 22a. The return vanes 30 contribute to the conversion of the handling fluid discharged from the impeller 1 from kinetic energy to pressure energy.

[0050] In the embodiment shown in Figure 1, the motor pump MP is divided into a suction-side region Ra, a discharge-side region Rb, and an intermediate region Rc between the suction-side region Ra and the discharge-side region Rb. The suction-side region Ra is the region between the suction casing 21 (more specifically, the suction port 21a of the suction casing 21) and the impeller 1 (more specifically, the side plate 11 of the impeller 1). The discharge-side region Rb is the region between the discharge casing 22 (more specifically, the discharge port 22a of the discharge casing 22) and the impeller 1 (more specifically, the main plate 10 of the impeller 1). Multiple blades 12 are arranged in the intermediate region Rc.

[0051] The rotor 2 and bearing 5 are located in the suction-side region Ra of the impeller 1. In this embodiment, the impeller 1 is equipped with side plates 11 that have a tapered shape that widens from the suction-side region Ra toward the discharge-side region Rb. Therefore, a space (dead space) is formed in the suction-side region Ra of the impeller 1. According to this embodiment, by arranging the rotor 2 and bearing 5 in the suction-side region Ra, the motor pump MP can have a structure that effectively utilizes the dead space, and as a result, can have a compact structure.

[0052] The bearing 5 comprises a rotating bearing body 6 mounted on a projection 17 of the side plate 11 and a stationary bearing body 7 mounted on the suction casing 21. The stationary bearing body 7 is positioned on the suction side of the rotating bearing body 6. The rotating bearing body 6 is a rotating member that rotates together with the rotation of the impeller 1, while the stationary bearing body 7 is a stationary member that does not rotate even when the impeller 1 rotates.

[0053] The rotating bearing body 6 has a cylindrical portion 6a having an outer diameter smaller than the inner diameter of the projection 17, and a flange portion 6b that protrudes outward from the cylindrical portion 6a. Therefore, the cross-section of the rotating bearing body 6 is L-shaped. A sealing member (for example, an O-ring) 31 is placed between the inner circumferential surface 17b of the projection 17 and the cylindrical portion 6a.

[0054] The rotating bearing body 6 is mounted on the projection 17 of the impeller 1 with the sealing member 31 attached to its cylindrical portion 6a. With the rotating bearing body 6 mounted, the rotor 2 is positioned adjacent to the flange portion 6b of the rotating bearing body 6.

[0055] The stationary bearing body 7 comprises a cylindrical portion 7a positioned opposite the cylindrical portion 6a of the rotating bearing body 6, and a flange portion 7b positioned opposite the flange portion 6b of the rotating bearing body 6. The cross-section of the stationary bearing body 7 is L-shaped, similar to the cross-section of the rotating bearing body 6. Seal members 32 and 33 are positioned between the cylindrical portion 7a of the stationary bearing body 7 and the suction casing 21. In this embodiment, two seal members 32 and 33 are positioned, but the number of seal members is not limited to this embodiment.

[0056] Figure 2 shows the flow of the handling fluid through the gap between the rotating bearing body and the stationary bearing body. Since the handling fluid is pressurized by the rotation of the impeller 1, the pressure of the handling fluid in the discharge region Rb is greater than the pressure of the handling fluid in the suction region Ra. Therefore, some of the handling fluid discharged from the impeller 1 flows back into the suction region Ra (see the black arrow in Figure 2).

[0057] More specifically, a portion of the fluid being handled passes through the gap between the stator casing 20 and the rotor 2 and flows into the gap between the flange portion 6b of the rotating bearing body 6 and the flange portion 7b of the stationary bearing body 7.

[0058] Figure 3 shows one embodiment of a plurality of grooves formed in the flange portion of the stationary bearing body. As shown in Figure 3, the stationary bearing body 7 has a plurality of grooves 40 formed in the flange portion 7b. These plurality of grooves 40 are formed on the surface of the flange portion 7b facing the flange portion 6b of the rotating bearing body 6. The plurality of grooves 40 are formed to generate dynamic pressure of the handling fluid in the gap between the flange portion 7b and the flange portion 6b. In this embodiment, the plurality of grooves 40 are spiral grooves extending in a helical shape. In one embodiment, the plurality of grooves 40 may be radial grooves extending radially. By forming the plurality of grooves 40, the bearing 5 can support the thrust load of the impeller 1 without contact.

[0059] In the embodiment shown in Figure 3, the multiple grooves 40 are formed in the flange portion 7b, but in one embodiment, the multiple grooves 40 may be formed in the flange portion 6b of the rotating bearing body 6. Even with such a formation, the bearing 5 can support the thrust load of the impeller 1 without contact.

[0060] Figure 4A shows one embodiment of a plurality of grooves formed in the cylindrical portion of the stationary bearing body. Figure 4A shows the plurality of grooves 41 as viewed from the direction of the center line CL. The stationary bearing body 7 may have a plurality of grooves 41 formed in the cylindrical portion 7a along the circumferential direction of the cylindrical portion 7a. In the embodiment shown in Figure 4A, the plurality of grooves 41 are arranged at equal intervals, but they may be arranged at unequal intervals.

[0061] These multiple grooves 41 are formed on the surface of the cylindrical portion 7a facing the cylindrical portion 6a of the rotating bearing body 6, and extend parallel to the cylindrical portion 7a (i.e., in the direction of the center line CL). In the embodiment shown in Figure 4A, each of the multiple grooves 41 has an arc-shaped recess when viewed from the direction of the center line CL. The shape of the multiple grooves 41 is not limited to this embodiment. In one embodiment, each of the multiple grooves 41 may have a concave shape when viewed from the direction of the center line CL.

[0062] Figures 4B and 4C show another embodiment of the groove formed in the cylindrical portion of the stationary bearing body. As shown in Figures 4B and 4C, the stationary bearing body 7 has an annular groove 42 formed in the cylindrical portion 7a along the circumferential direction of the cylindrical portion 7a. The groove 42 is formed in a part of the cylindrical portion 7a and has a concave shape when viewed from a direction perpendicular to the centerline CL direction (see Figures 4B and 4C). The cylindrical portion 7a is present at both ends 42a, 42a of the groove 42 in the centerline CL direction. With this structure, even when a radial load is applied to the impeller 1, the stationary bearing body 7 (more specifically, the cylindrical portion 7a) can reliably support the impeller 1 via the rotating bearing body 6. The length of the groove 42 in the centerline CL direction is not particularly limited. In the embodiments shown in Figures 4B and 4C, the stationary bearing body 7 has a single groove 42, but in one embodiment, the stationary bearing body 7 may have a plurality of grooves 42 arranged along the centerline CL direction.

[0063] The handling fluid that passes through the gap between flange portion 6b and flange portion 7b flows into the gap between cylindrical portion 6a and cylindrical portion 7a. When the rotating side bearing body 6 rotates together with the impeller 1, viscous resistance is generated in the handling fluid flowing through this gap. This viscous resistance may adversely affect the operating efficiency of the motor pump MP.

[0064] As shown in the embodiment described above, by forming multiple grooves 41 (or grooves 42), the size of the narrow region formed in the gap between the cylindrical portion 6a and the cylindrical portion 7a is reduced. Therefore, the viscous resistance generated in the handling fluid can be reduced. Furthermore, by forming multiple grooves 41 (or grooves 42), dynamic pressure is generated in the handling fluid, and the bearing 5 can support the radial load of the impeller 1 without contact. The effect of reducing viscous resistance by reducing the size of the narrow region formed between the flange portion 6b and the flange portion 7b can also be achieved by providing multiple grooves 40 (see Figure 3).

[0065] In the embodiments shown in Figures 4A to 4C, the grooves 41 and 42 are formed in the cylindrical portion 7a, but in one embodiment, the grooves 41 and 42 may be formed in the cylindrical portion 6a of the rotating bearing body 6. Even with such a formation, the bearing 5 can support the radial load of the impeller 1 without contact.

[0066] As shown in Figure 2, the handling fluid that passes through the gap between the cylindrical portion 6a of the rotating bearing body 6 and the cylindrical portion 7a of the stationary bearing body 7 passes through the gap between the side plate 11 of the impeller 1 and the suction casing 21 and is returned to the suction side of the motor pump MP. In this embodiment, the bearing 5 is positioned in the path of the leakage flow of the handling fluid. With this configuration, a portion of the handling fluid flows into the minute gap between the rotating bearing body 6 and the stationary bearing body 7, and as a result, the motor pump MP can suppress leakage of the handling fluid.

[0067] As described above, the pressure of the fluid being handled in the discharge region Rb is greater than the pressure of the fluid being handled in the suction region Ra. Therefore, a thrust load acts on the impeller 1 from the discharge port 22a of the discharge casing 22 toward the suction port 21a of the suction casing 21 (see the white arrow in Figure 1). The motor pump MP according to this embodiment has a structure that reduces the thrust load.

[0068] Figure 5A shows one embodiment of a thrust load reduction structure provided on the back of an impeller. Figure 5B is a view of Figure 5A from the direction of arrow A. As shown in Figures 5A and 5B, the motor pump MP is equipped with a thrust load reduction structure 45 provided on the back of the impeller 1 (more specifically, on the main plate 10). In the embodiments shown in Figures 5A and 5B, the thrust load reduction structure 45 is a plurality of spirally extending back blades 46 attached to the main plate 10. These plurality of back blades 46 can generate a load in the opposite direction to the thrust load due to the rotation of the impeller 1. As a result, the thrust load reduction structure 45 can reduce the thrust load generated in the motor pump MP.

[0069] Figure 6 shows another embodiment of the thrust load reduction structure. As shown in Figure 6, the thrust load reduction structure 45 may be a plurality of notches formed along the circumferential direction of the impeller 1 (more specifically, the main plate 10) and extending toward the center of the impeller 1. In the embodiment shown in Figure 6, a plurality of notches 47 are formed in the main plate 10 of the impeller 1. By forming a plurality of notches 47, the contact area of ​​the handling fluid with the main plate 10 is reduced. As a result, the thrust load reduction structure 45 can reduce the thrust load generated in the motor pump MP. Although not shown, the embodiment shown in Figure 5 and the embodiment shown in Figure 6 may be combined.

[0070] In this embodiment, the impeller 1 is always subjected to a thrust load from the discharge side towards the suction side. Furthermore, the bearing 5 supports the impeller 1 that generates rotational force. Therefore, the parallelism of the impeller 1 itself is maintained, and wobbling of the impeller 1 can be suppressed. As a result, with a structure that only places a single bearing 5 in the suction side region Ra (i.e., a single bearing structure), the motor pump MP can continue to operate stably.

[0071] In one embodiment, at least one of the impeller 1 and bearing 5 may be made of a lightweight material. Examples of lightweight materials include resin or metals with low specific gravity (e.g., aluminum alloy, magnesium alloy, titanium alloy, etc.). Such a structure can reduce the weight of the motor pump MP itself, and furthermore, it can make the bearing 5 (and impeller 1) more compact. The material of the components that come into contact with the liquid (i.e., wetted components), such as the impeller 1 and bearing 5, is not particularly limited and can be changed to any material as appropriate depending on the liquid quality.

[0072] Furthermore, in this embodiment, the multiple return vanes 30 (see Figure 1) can reduce the radial load generated on the impeller 1. The multiple return vanes 30 are arranged at equal intervals along the circumferential direction of the discharge port 22a. With this arrangement, the radial load is evenly distributed, and as a result, the radial load generated on the impeller 1 is reduced.

[0073] In this embodiment, the motor pump MP is equipped with a permanent magnet motor. Therefore, when the motor pump MP is started, a certain load acts on the bearing 5 to convert the repulsive force caused by the magnetic force into rotational force. This load is a force generated on the rotor 2, and the bearing 5 supports this load.

[0074] Figures 7A and 7B show a rotor positioned offset from the stator. As shown in Figure 7A, when the rotor 2 is positioned offset towards the discharge side relative to the stator 3, the impeller 1 is subjected to a force acting in a direction that brings the rotating side bearing body 6 closer to the stationary side bearing body 7 due to the influence of the magnetic force generated between the rotor 2 and the stator 3 (see arrow in Figure 7A). This arrangement allows for adjustment (increase) of the thrust load of the rotating side bearing body 6 acting on the stationary side bearing body 7.

[0075] As shown in Figure 7B, when the rotor 2 is positioned offset towards the suction side relative to the stator 3, the impeller 1 is subjected to a force acting in a direction that causes the rotating side bearing body 6 to move away from the stationary side bearing body 7 due to the influence of the magnetic force generated between the rotor 2 and the stator 3 (see Figure 7B). This arrangement allows for adjustment (reduction) of the thrust load on the rotating side bearing body 6 acting on the stationary side bearing body 7.

[0076] Figure 8 shows an embodiment of a bearing having a tapered structure. In the embodiment shown in Figure 8, the bearing 5 has a tapered structure in which the gap between the rotating bearing body 6 and the stationary bearing body 7 extends in a direction that approaches the center line CL (i.e., the central part of the impeller 1) from the suction side to the discharge side. As shown in Figure 8, the rotating bearing body 6 and the stationary bearing body 7 each have inclined surfaces 50 and 51 that face each other. With this configuration, the bearing 5 can concentrate the radial load and thrust load acting on the rotating bearing body 6 and the stationary bearing body 7 on the inclined surfaces 50 and 51, and the bearing 5 can have a simple structure.

[0077] Figure 9 shows another embodiment of a bearing having a tapered structure. In the embodiment shown in Figure 9, the bearing 5 has a tapered structure in which the gap between the rotating bearing body 6 and the stationary bearing body 7 extends in a direction away from the center line CL (i.e., the central part of the impeller 1) from the suction side to the discharge side. As shown in Figure 9, the rotating bearing body 6 and the stationary bearing body 7 each have inclined surfaces 53 and 54 facing each other.

[0078] Figure 10 shows a pump unit equipped with multiple motor pumps. As shown in Figure 10, the pump unit PU may include multiple motor pumps MP arranged in series and an inverter 60 that controls the operation of each of the multiple motor pumps MP. In the embodiment shown in Figure 10, each of the multiple motor pumps MP has the same structure as shown in the embodiment described above. Therefore, a detailed description of the motor pumps MP is omitted.

[0079] In the embodiment shown in Figure 10, the pump unit PU is equipped with three motor pumps MP, but the number of motor pumps MP is not limited to this embodiment. As described above, the suction port 21a and discharge port 22a of the pump unit PU are arranged in a straight line along the center line CL. Therefore, multiple motor pumps MP can be arranged in a straight line in a continuous manner, and the pump unit PU can easily have a multi-stage motor pump structure.

[0080] As shown in Figure 10, two intermediate casings 61 are positioned between the suction casing 21, which is adjacent to the first-stage impeller 1A, and the discharge casing 22, which is adjacent to the third-stage impeller 1C. The second-stage impeller 1B is positioned between these intermediate casings 61, 61. Each of the intermediate casings 61, 61 has a structure common to (i.e., similar to) the suction casing 21. The worker can assemble the pump unit by inserting through bolts 25 into the suction casing 21, the intermediate casings 61, 61, and the discharge casing 22, with the intermediate casings 61, 61 sandwiched between the suction casing 21 and the discharge casing 22, and then tightening them.

[0081] As shown in Figure 10, one inverter 60 is connected to the stator 3 of multiple motor pumps MP. The inverter 60 can independently control each of the multiple motor pumps MP. Therefore, the operator can operate at least one motor pump MP at any time according to the operating conditions of the pump unit.

[0082] Figures 11 and 12 illustrate other embodiments of the pump unit. In the embodiments shown in Figures 11 and 12, the pump unit PU comprises a plurality of motor pumps MP arranged in parallel. In Figure 11, although simplified, each of these motor pumps MP is installed inside the piping 65. In Figure 11, four motor pumps MP are provided, but the number of motor pumps MP is not limited to this embodiment. As shown in Figure 12, three motor pumps MP may be provided.

[0083] Figure 13A shows a motor pump as a comparative example. Figures 13B and 13C show other embodiments of the motor pump. As shown in Figure 13A, the motor pump as a comparative example has a rotating shaft RS, but the motor pump MP according to this embodiment does not have a rotating shaft RS. Instead, the impeller 1 has a rounded protrusion 70 located in its central portion.

[0084] In the embodiment shown in Figure 13B, the impeller 1 has a protrusion 70A having a first radius of curvature, and in the embodiment shown in Figure 13C, the impeller 1 has a protrusion 70B having a second radius of curvature different from the first radius of curvature. Hereinafter, the protrusions 70A and 70B may be referred to simply as the protrusion 70 without distinction.

[0085] The protrusion 70 is positioned in the central part of the main plate 10 and is integrally formed with the main plate 10. In one embodiment, the protrusion 70 may be made of a different material from the main plate 10. In this case, the protrusion 70 may be replaced with one having a different radius of curvature depending on the operating conditions of the motor pump.

[0086] The tip 71 of the protrusion 70 has a smooth convex shape, and the handling fluid flowing into the impeller 1 comes into contact with the tip 71 of the protrusion 70. By providing the protrusion 70, the handling fluid is guided to the blade 12 smoothly and efficiently without its flow being obstructed. On the other hand, in a motor pump as a comparative example, the rotating shaft RS is fixed to the impeller by a nut Nt, so the flow of the handling fluid may be obstructed by the nut Nt (and the rotating shaft RS).

[0087] The protrusion 70A shown in Figure 13B has a larger radius of curvature than the protrusion 70B shown in Figure 13C. By increasing the radius of curvature of the protrusion 70, the distance between the protrusion 70 and the side plate 11 decreases. Conversely, by decreasing the radius of curvature of the protrusion 70, the distance between the protrusion 70 and the side plate 11 increases. In this way, by changing the radius of curvature of the protrusion 70, the size of the flow path of the impeller 1 for the handled liquid can be adjusted. The flow path of the impeller 1 shown in Figure 13C is larger than the flow path of the impeller 1 shown in Figure 13B.

[0088] According to this embodiment, since the motor pump MP does not have a rotating shaft, the number of parts can be reduced, and the size of the flow path can be adjusted. Furthermore, since there is no need to provide a rotating shaft, the impeller 1 can have a compact size. As a result, the entire motor pump MP can have a compact size.

[0089] The motor pump rotates impeller 1 at high speed during operation. If the center of gravity of impeller 1 is misaligned, impeller 1 will rotate at high speed in an eccentric state. As a result, noise may be generated, and in the worst case, the motor pump may fail.

[0090] Therefore, the operator performs a balance (dynamic balance) adjustment method to determine the center of gravity of the impeller 1 to a desired position. As shown in Figure 13A, if a rotating shaft RS is attached to the impeller, it is necessary to attach the rotating shaft RS to the testing machine and rotate the impeller together with the rotating shaft RS. In this embodiment, since the rotating shaft RS is not attached to the impeller 1, the operator can perform the balance adjustment method described below.

[0091] Figures 14 to 18 illustrate one embodiment of the balance adjustment method. As shown in Figure 14, first, the worker performs the step of forming a through hole 10a in the center of the impeller 1 (more specifically, the main plate 10). Then, as shown in Figure 15, the worker inserts the shaft 76 of the balance adjustment jig 75 into the through hole 10a. The shaft 76 of the balance adjustment jig 75 corresponds to the rotation axis.

[0092] Subsequently, as shown in Figure 16, the worker places the fixing body 77 on the rear side of the impeller 1 and fastens the shaft 76 to the fixing body 77. In this state, the worker rotates the impeller 1 together with the balance adjustment jig 75 and performs the process of determining the center of gravity of the impeller 1 and adjusting the center of gravity. Thus, the balance adjustment jig 75 has a structure that supports the center of the impeller 1. For this reason, the balance adjustment jig 75 may also be called a center support adjustment jig.

[0093] After determining the center of gravity of the impeller 1 to the desired position, the operator withdraws the shaft 76 of the balance adjustment jig 75, and then inserts the center cap 80 into the through hole 10a to close the through hole 10a (see Figures 17 and 18). The center cap 80 has a rounded shape, similar to the protrusion 70 in the embodiment shown in Figures 13B and 13C. Therefore, the handling fluid is guided to the blade 12 smoothly and efficiently without its flow being obstructed.

[0094] Figure 19 shows another embodiment of the balance adjustment jig. In the embodiment shown in Figure 18, the balance adjustment jig 75 has a structure that supports the center of the impeller 1. In the embodiment shown in Figure 19, the balance adjustment jig 85 includes a supporter 86 that supports the rotating side bearing body 6 of the bearing 5, and a shaft portion 87 fixed to the supporter 86. Thus, the balance adjustment jig 85 has a structure that supports the end of the impeller 1. Therefore, the balance adjustment jig 85 may also be called an edge support adjustment jig.

[0095] The supporter 86 has an annular shape with an outer diameter smaller than the inner diameter of the rotating bearing body 6. By inserting the supporter 86 into the rotating bearing body 6, the balance adjustment jig 85 supports the impeller 1 via the rotating bearing body 6. In this state, the operator performs the step of rotating the impeller 1 together with the balance adjustment jig 85. After that, the operator determines the center of gravity of the impeller 1 while it is rotating and performs the step of adjusting the center of gravity.

[0096] According to the embodiment shown in Figure 19, the operator does not need to form the through hole 10a. In the embodiment shown in Figure 19, the impeller 1 may also have a protrusion 70 formed at its central position (see Figures 13A and 13B).

[0097] Figure 20 shows another embodiment of the balancing method. As shown in Figure 20, the rotor 2 comprises an annular iron core 2a and a plurality of magnets 2b embedded in the iron core 2a. The plurality of magnets 2b are arranged at equal intervals along the circumferential direction of the rotor 2 (more specifically, the iron core 2a). An operator performs the step of forming a plurality of weight insertion holes 90 along the circumferential direction of the rotor 2. This step of forming the weight insertion holes 90 is performed during the manufacturing of the iron core 2a.

[0098] The weight insertion holes 90 are formed between adjacent magnets 2b. The operator performs a step to determine the center of gravity of the impeller 1 and determines the current center of gravity of the impeller 1. If the center of gravity of the impeller 1 is off, the operator performs a step to adjust the center of gravity by inserting a weight 91 into at least one of the multiple weight insertion holes 90.

[0099] In one embodiment, if the center of gravity of the impeller 1 is misaligned, the worker may, instead of inserting the weight 91 into the weight insertion hole 90, remove the excess weight that is causing the misalignment of the center of gravity of the impeller 1.

[0100] Figure 21A is a perspective view showing another embodiment of the pump unit. Figure 21B is a plan view of the pump unit shown in Figure 21A. As shown in Figures 21A and 21B, the pump unit PU comprises a plurality of motor pumps MP (three in this embodiment), a control device 100 for variable-speed operation of the plurality of motor pumps MP, and a current sensor 101 that is electrically connected to the control device 100 and detects the current supplied to the plurality of motor pumps MP.

[0101] In this embodiment, two current sensors 101 are provided, but at least one current sensor 101 may be provided. Examples of current sensors 101 include Hall elements and CTs (current converters).

[0102] The pump unit PU comprises power lines 105 and signal lines 106 extending from multiple motor pumps MP, and a protective cover 107 protecting the current sensor 101, power lines 105, and signal lines 106. The power lines 105 and signal lines 106 are electrically connected to the inverter 60.

[0103] Between the multiple motor pumps MP are U-phase, V-phase, and W-phase copper bars (in other words, energized plates, copper plates) 108, and the current sensor 101 is connected to one of these copper bars 108. Each motor pump MP is equipped with a terminal block 102, and the copper bars 108 are connected to the terminal block 102.

[0104] The control device 100 is electrically connected to the inverter 60 and is configured to control the operation of the motor pump MP via the inverter 60. The control device 100 may be located outside the inverter 60 or inside the inverter 60.

[0105] The control device 100 includes a signal receiving unit 100a that receives signals from the current sensor 101 via a signal line 106, a storage unit 100b that stores information and operating programs related to the operation of the motor pump MP, and a control unit 100c that controls the operation of the motor pump MP based on the data received by the signal receiving unit and the data stored in the storage unit.

[0106] In this embodiment, the pump unit PU is equipped with one inverter 60 for multiple motor pumps MP, but the pump unit PU may be equipped with a number of inverters 60 corresponding to the number of motor pumps MP. When multiple motor pumps MP are arranged, each of the multiple inverters 60 controls the operation of each of the multiple motor pumps MP by the control device 100.

[0107] As described above, the motor pump MP has a compact structure that makes effective use of dead space. Therefore, by connecting multiple motor pumps MP in series, the pump unit PU can operate at a high head without increasing its installation area.

[0108] The motor pump MP is a rotating machine equipped with a permanent magnet motor. Such a motor rotates uncontrolled by forcibly applying voltage at startup. Control of the rotational speed of the motor pump MP by the inverter 60 starts immediately, after which steady-state operation of the motor pump MP begins.

[0109] In this embodiment, the pump unit PU is equipped with multiple motor pumps MP. Therefore, there is no problem if the rotational speed difference between the multiple motor pumps MP is eliminated before control of the rotational speed of the motor pumps MP is started. However, if the rotational speed difference is not eliminated, there is a possibility that a motor pump MP has failed to start.

[0110] Generally, increasing the number of magnetic poles of the rotor 2 allows the motor pump MP to rotate more smoothly, and the difference in rotational speed between multiple motor pump MPs is more easily eliminated. In this embodiment, the motor pump MP has a structure that forms a flow path inside the rotor 2, and the outer diameter of the rotor 2 is designed to be large.

[0111] When the outer diameter of the rotor 2 is large, the size of the rotor 2 in the outer circumference direction increases, making it easy to arrange multiple magnets and increase the number of magnetic poles. With this configuration, the pump unit PU can eliminate the rotational speed difference between multiple motor pumps MP. Furthermore, in this embodiment, by using inexpensive planar magnets, the rotor 2 can be made more cost-effective compared to a typical motor that uses curved magnets.

[0112] Furthermore, in this embodiment, the motor pump MP has a canned motor structure in which the stator 3 is housed in the stator casing 20, and the distance between the rotor 2 and the stator 3 is larger than that of a typical motor. Therefore, the motor pump MP can reduce torque ripple, which means the range of torque fluctuations, and as a result, the pump unit PU can eliminate the rotational speed difference between multiple motor pumps MP.

[0113] Thus, while the pump unit PU can eliminate the rotational speed difference, it is desirable to operate the motor pump MP more stably during startup and / or steady-state operation.

[0114] Therefore, the control method for the motor pump MP will be described below. In this embodiment, multiple motor pumps MP are connected in series. In this case, if the liquid being handled contains foreign matter, the foreign matter may become entangled in the motor pump MP (especially the first motor pump MP), and as a result, the operation of the pump unit PU may be hindered by the foreign matter. Furthermore, for some reason, the difference in rotational speed between the multiple motor pumps MP may not be resolved.

[0115] Figure 22 shows the control flow of the motor pump by the control device. As shown in step S101 of Figure 22, the control device 100, which is electrically connected to the inverter 60, measures the current value of multiple motor pumps MP (more specifically, the sum of the current values ​​of each motor pump MP) during the current operation of the motor pumps MP based on the output current of the inverter 60.

[0116] Subsequently, the control device 100 calculates a lower limit current value based on the assumed current value expected during normal operation of the motor pump MP (more specifically, during startup and steady-state operation), and compares the sum of the measured current values ​​(measured current value Amax) with a predetermined lower limit current value (see step S102). In one embodiment, the storage unit 100b of the control device 100 stores the assumed current value of each motor pump MP and the assumed current values ​​of multiple motor pump MPs. The storage unit 100b may calculate the assumed current values ​​of multiple motor pump MPs from the assumed current value of each motor pump MP.

[0117] The control device 100 may determine the "expected current value during normal operation" based on at least one of the rated current value and allowable current value of each motor pump MP, or it may determine the "expected current value during normal operation" based on the current value when multiple motor pumps MP are in operation.

[0118] In one embodiment, the control device 100 determines the lower limit current value based on the number of motor pumps MP. For example, the lower limit current value is calculated using the following formula. Lower limit current value = Assumed current value of multiple motor pumps MP × (1 - 1 / number of motor pumps n) In this embodiment, since three motor pumps MP are arranged, the lower limit current value is 2 / 3 of the assumed current value.

[0119] After step S102, the control device 100 compares the calculated lower limit current value with the measured current value (see step S103). More specifically, the control device 100 determines whether the measured current value is lower than the lower limit current value (measured current value Amax > lower limit current value).

[0120] If the measured current value is lower than the lower limit current value (see "YES" in step S103), in this embodiment, if the measured current value is below 2 / 3 of the assumed current value (i.e., the lower limit current value), the control device 100 determines that an abnormality has occurred in at least one of the motor pumps MP (see step S104). If the measured current value has not decreased below the lower limit current value (see "NO" in step S103), the control device 100 repeats steps S102 and S103.

[0121] If the control device 100 determines that an abnormality has occurred, the control device 100 may continue operating the motor pump MP and issue an alarm, or it may stop operating the motor pump MP and issue an alarm.

[0122] Such a control flow may be performed when the motor pump MP is started up, or during steady-state operation of the motor pump MP. When the control flow is performed when the motor pump MP is started up, the measured current value corresponds to the starting current value when multiple motor pump MPs are started up, and the assumed current value is the current value that is expected when multiple motor pump MPs are started up under normal conditions.

[0123] When performing control flow during steady-state operation of motor pumps MP, the measured current value corresponds to the operating current value during steady-state operation of multiple motor pumps MP, and the assumed current value is the current value expected during normal steady-state operation of multiple motor pumps MP.

[0124] The starting current value and the operating current value may be the same or different. Similarly, the expected current value during normal startup and the expected current value during normal steady-state operation may be the same or different.

[0125] In one embodiment, the control device 100 may determine the assumed current value based on the flow rates on the discharge side of a plurality of motor pumps MP. In this case, the pump unit PU is equipped with a flow sensor (not shown) that detects the flow rate of the liquid being handled, and the flow sensor is electrically connected to the control device 100.

[0126] The storage unit 100b of the control device 100 stores data showing the correlation between the flow rate of the fluid being handled during normal operation and the current supplied to multiple motor pumps MP during normal operation. Based on this data, the control device 100 determines an assumed current value and calculates a lower limit current value based on the determined assumed current value. The above calculation formula can be given as an example of a formula for calculating the lower limit current value.

[0127] The control device 100 compares the measured current value during steady-state operation of multiple motor pumps MP with the lower limit current value, and if the measured current value is lower than the lower limit current value, it determines that an abnormality has occurred in at least one of the multiple motor pumps MP.

[0128] In one embodiment, the control device 100 may determine the assumed current value based on the pressure on the discharge side of a plurality of motor pumps MP. In this case, the pump unit PU is equipped with a pressure sensor (not shown) that detects the pressure of the liquid being handled, and the pressure sensor is electrically connected to the control device 100.

[0129] The memory unit 100b of the control device 100 stores data showing the correlation between the pressure of the fluid being handled and the current supplied to multiple motor pumps MP during normal operation. Based on this data, the control device 100 determines an assumed current value and calculates a lower limit current value based on the determined assumed current value. The above calculation formula can be given as an example of a formula for calculating the lower limit current value.

[0130] The control device 100 compares the measured current value during steady-state operation of multiple motor pumps MP with the lower limit current value, and if the measured current value is lower than the lower limit current value, it determines that an abnormality has occurred in at least one of the multiple motor pumps MP.

[0131] In the embodiments shown in Figures 21A and 21B, the pump unit PU includes a current sensor 101 (first current sensor 101) positioned between the first motor pump MP (first motor pump MP) and the second motor pump MP (second motor pump MP), and a current sensor 101 (second current sensor 101) positioned between the second motor pump MP and the third motor pump MP (third motor pump MP).

[0132] Therefore, the control device 100 can measure the current value of the first motor pump MP (i.e., the measured current value Aa1) based on the signal sent from the first current sensor 101, and measure the sum of the measured current value Aa1 of the first motor pump MP and the measured current value Aa2 of the second motor pump MP (i.e., the measured current value Ab (= Aa1 + Aa2)) based on the signal sent from the second current sensor 101.

[0133] The control device 100 compares the measured current value Aa1 with the expected current value that is expected during normal operation of each motor pump MP (startup and steady-state operation). If the measured current value Aa1 is lower than the expected current value (Aa1 < expected current value), it determines that an abnormality has occurred in the first motor pump MP.

[0134] The control device 100 compares the measured current value Aa1 with the expected current value expected during normal operation of each motor pump MP (startup and steady-state operation). If the measured current value Aa1 is greater than the expected current value (Aa1 > expected current value), and the value obtained by subtracting the measured current value Aa1 from the measured current value Ab (i.e., Ab - Aa1) is less than the expected current value ((Ab - Aa1) < expected current value), the control device 100 determines that an abnormality has occurred in the second motor pump MP. The value obtained by subtracting the measured current value Aa1 from the measured current value Ab corresponds to the measured current value Aa2.

[0135] If the control device 100 determines that the measured current value Amax is lower than the lower limit current value, and that there are no abnormalities in the first motor pump MP and the second motor pump MP, then it determines that there is an abnormality in the third motor pump MP.

[0136] If the pump unit PU is equipped with four motor pumps MP connected in series, the pump unit PU is equipped with a current sensor 101 (third current sensor 101) located between the third motor pump MP and the fourth motor pump MP (fourth motor pump MP).

[0137] The control device 100 can measure the sum of the measured current value Aa1 of the first motor pump MP, the measured current value Aa2 of the second motor pump MP, and the measured current value Aa3 of the third motor pump MP (i.e., the measured current value Ac) based on the signal sent from the third current sensor 101.

[0138] The control device 100 determines that an abnormality has occurred in the third motor pump MP if the measured current value Aa1 is greater than the assumed current value (Aa1 > assumed current value), the value obtained by subtracting the measured current value Aa1 from the measured current value Ab (i.e., Ab - Aa1) is greater than the assumed current value ((Ab - Aa1) > assumed current value), and the value obtained by subtracting the measured current value Ab from the measured current value Ac (i.e., Ac - Ab, where Ab = Aa1 + Aa2) is lower than the assumed current value. The value obtained by subtracting the measured current value Ab from the measured current value Ac corresponds to the assumed current value Aa3.

[0139] The control device 100 determines that the measured current value Amax is lower than the lower limit current value, and that there are no abnormalities in the first motor pump MP, the second motor pump MP, and the third motor pump MP, and then determines that there is an abnormality in the fourth motor pump MP. Even when the pump unit PU is equipped with five or more motor pump MPs connected in series, the control device 100 can determine the abnormality of each motor pump MP in the same manner as described above.

[0140] In the embodiments described above, a method for controlling multiple motor pumps MP connected in series was explained, but the pump unit PU may also control multiple motor pumps MP connected in parallel. When controlling multiple motor pumps MP connected in parallel (see Figures 11 and 12), the control device 100 may be configured to stagger the start timing of each of the multiple motor pumps MP.

[0141] By staggering the start timing, the pump unit PU can create a swirling flow within the piping 65. This swirling flow removes foreign matter and air adhering to the piping 65, and further prevents stagnation of the liquid being handled.

[0142] To form a swirling flow, the control device 100 may start one of the multiple motor pumps MP (the first motor pump MP), and then start the motor pump MP adjacent to the started motor pump MP (i.e., the first motor pump MP) (the second motor pump MP). By starting adjacent motor pump MPs in succession in this way, the pump unit PU can form a swirling flow that rotates in accordance with the starting sequence of the motor pump MPs.

[0143] For example, if three motor pumps MP are installed, the control device 100 may start the first motor pump MP and then start the second motor pump MP, or it may start the third motor pump MP and then start the first motor pump MP adjacent to the third motor pump MP.

[0144] Figure 23 shows another embodiment of the impeller. In this embodiment, the bearing 5 is not shown. In the embodiment described above, the impeller 1 has an annular projection 17 extending from the outer edge 11a of the side plate 11 toward the suction portion 15 (see Figure 1). In the embodiment shown in Figure 23, the side plate 11 of the impeller 1 has an annular projection 117 located radially inward from the outer edge 11a of the side plate 11.

[0145] The rotor 2 is positioned in an annular stepped portion formed between the outer edge 11a and the projection 117 of the side plate 11, and the exposed portion of the rotor 2 is covered by the cover 110. The cover 110 is one of the components of the motor pump MP. Examples of the cover 110 include corrosion-resistant can, resin coating, or Ni plating.

[0146] In one embodiment, the iron core 2a of the rotor 2 is joined to the projection 117 by means of adhesive, press-fitting, shrink-fitting, welding, etc. Similarly, the cover 110 is joined to the impeller 1 by means of adhesive, press-fitting, shrink-fitting, welding, etc.

[0147] Figure 24 shows another embodiment of the impeller. In this embodiment, the bearing 5 is not shown. As shown in Figure 24, the impeller 1 may include an annular mounting portion 118 located radially outward from the projection 117. By inserting the rotor 2 into the annular space between the mounting portion 118 and the projection 117, the rotor 2 can be more securely fixed to the side plate 11. In this embodiment as well, the exposed portion of the rotor 2 is covered by the cover 110.

[0148] Figure 25 shows a sealing member positioned between the cover and the side plate. In this embodiment, the bearing 5 is not shown. As shown in Figure 25, by positioning sealing members (e.g., O-rings) 120, 121 between the cover 110 and the side plate 11 (more specifically, the outer edge 11a and projection 117 of the side plate 11), contact of the liquid with the rotor 2 can be reliably prevented.

[0149] The impeller 1 according to the embodiments shown in Figures 1 to 25 is manufactured by means such as casting, stainless steel press molding, or resin molding. Similarly, the impeller 1 according to the embodiments shown in Figures 26 to 34, which will be described below, may also be manufactured by means such as casting, stainless steel press molding, or resin molding.

[0150] Figure 26 shows another embodiment of the impeller. In this embodiment, the bearing 5 is not shown. As shown in Figure 26, the rotor 2 is fixed to the outer edge 11a of the side plate 11 so as to obstruct the flow path of the impeller 1 (i.e., the outlet flow path) formed between the main plate 10 and the side plate 11. In this embodiment as well, the rotor 2 is located in the suction side region Ra.

[0151] In the embodiment shown in Figure 26, the rotor 2 is not covered by the cover 110, and the rotor 2 is made of a corrosion-resistant material. In the embodiments described above, the rotor 2 does not necessarily need to be covered by the cover 110 and may be made of a corrosion-resistant material. In one embodiment, the rotor 2 may be covered by the cover 110.

[0152] With this configuration, the handling fluid passing through the outlet channel collides with the inner surface of the rotor 2, and its direction is changed. The handling fluid then passes through the gap between the main plate 10 and the discharge casing 22 and is discharged from the discharge port 22a.

[0153] In the embodiments shown in Figures 23 to 26, the rotor 2 and bearing 5 are located in the suction-side region Ra of the impeller 1, so the motor pump MP has a compact structure.

[0154] Figure 27 shows another embodiment of the motor pump. As shown in Figure 27, the motor pump MP comprises a first impeller 1A located on the suction port 21a side, a second impeller 1B located on the discharge port 22a side, and a connecting shaft 126 connected to the first impeller 1A and the second impeller 1B. The rotor 2 is fixed to the first impeller 1A, and the stator 3 is located radially outward from the rotor 2. A bearing 5 supports the first impeller 1A, and the second impeller 1B is supported by the bearing 5 via the connecting shaft 126.

[0155] In the embodiment shown in Figure 27, the motor pump MP includes an intermediate casing 125 positioned between the first impeller 1A and the second impeller 1B. The intermediate casing 125 is an annular partition separating the discharge side of the first impeller 1A from the suction side of the second impeller 1B. In this embodiment, the intermediate casing 125 is fixed to the stator casing 20.

[0156] In the embodiment shown in Figure 27, the motor pump MP is equipped with two impellers 1, but the number of impellers 1 is not limited to this embodiment. The motor pump MP may be equipped with multiple intermediate casings 125 depending on the number of impellers 1. In other words, the motor pump MP may be equipped with multiple impellers 1, including at least a first impeller 1A and a second impeller 1B.

[0157] Figure 28 shows another embodiment of the motor pump. As shown in Figure 28, the motor pump MP further includes a discharge-side bearing 128 that rotatably supports the communication shaft 126 and is located on the discharge side of the second impeller 1B. The discharge-side bearing 128 is mounted on the discharge casing 22, and sealing members (e.g., O-rings) 127A and 127B are placed in the gap between the discharge-side bearing 128 and the discharge casing 22. In the embodiment shown in Figure 28, the motor pump MP also has two impellers 1, but the number of impellers 1 is not limited to this embodiment. The motor pump MP may have a plurality of impellers 1, including at least a first impeller 1A and a second impeller 1B.

[0158] As shown in Figure 28, the discharge casing 22 has a flow path 129 that communicates with the discharge port 22a. The flow path 129 is located radially outward from the communication shaft 126. The handling liquid discharged from the second impeller 1B is discharged to the outside through the flow path 129 and the discharge port 22a.

[0159] In the embodiment shown in Figure 28, the first impeller 1A and the second impeller 1B are supported not only by the bearing 5 but also by the discharge-side bearing 128. The discharge-side bearing 128 is a radial bearing. With this structure, the motor pump MP can suppress radial displacement of the first impeller 1A and the second impeller 1B.

[0160] Figure 29 shows another embodiment of the motor pump. As shown in Figure 29, the motor pump MP may include a communication shaft 126 to which a single impeller 1 is fixed, and a discharge-side bearing 128 that rotatably supports the communication shaft 126.

[0161] Figure 30 shows a motor pump in which various components can be selected according to operating conditions. In Figure 30, the horizontal axis represents the flow rate and the vertical axis represents the head. As shown in Figure 30, the motor pump MP is configured to allow the selection of optimal components according to various operating conditions (i.e., the magnitude of the flow rate and the magnitude of the head).

[0162] In the embodiment shown in Figure 30, the motor pump MP can be selected from a plurality of (four in this embodiment) different configurations depending on the size of the head and the size of the flow rate (see MPA to MPD in Figure 30). In this embodiment, the motor pump MP comprises a plurality of impellers 1 of different sizes, a plurality of rotors 2 fixed to the plurality of impellers 1 and having different lengths, a plurality of stators 3 having a length corresponding to the length of the plurality of rotors 2, and a plurality of stator casings 20 that house the plurality of stators 3 and have a length corresponding to the length of the plurality of stators 3.

[0163] The motor capacity of the motor pump MP depends on the length Lg of the stator 3. The head of the motor pump MP depends on the diameter D1 of the impeller 1. The flow rate of the motor pump MP depends on the size of the outlet passage B2 of the impeller 1.

[0164] Multiple impellers 1 comprise multiple side plates 11 having the same diameter and multiple main plates 10 having different diameters. In this specification, the diameter D1 of the impeller 1 corresponds to the diameter of the main plates 10.

[0165] The relationship between motor pumps MPA and MPB will be explained. As shown in Figure 30, motor pumps MPA and MPB have the same motor capacity (i.e., LgA = LgB). Motor pump MPA has a higher head capacity than motor pump MPB (i.e., D1A > D1B). Motor pump MPB has a higher flow capacity than motor pump MPA (i.e., B2B > B2A).

[0166] This section explains the relationship between motor pumps MPA and MPC. A motor pump MPC has a larger motor capacity than a motor pump MPA (i.e., LgC > LgA). A motor pump MPC has the same head capacity as a motor pump MPA (i.e., D1A = D1C). A motor pump MPC has a higher flow rate capacity than a motor pump MPA (i.e., B2C > B2A).

[0167] This section explains the relationship between motor pump MPB and motor pump MPC. Motor pump MPC has a larger motor capacity than motor pump MPB (i.e., LgC > LgB). Motor pump MPC has a higher head capacity than motor pump MPB (i.e., D1C > D1B). The outlet passage B2B of impeller 1 of motor pump MPB is the same size as, or larger than, the outlet passage B2C of impeller 1 of motor pump MPC (i.e., B2B ≥ B2C).

[0168] This section explains the relationship between motor pumps MPC and MPD. Motor pump MPC has the same motor capacity as motor pump MPD (i.e., LgC = LgD). Motor pump MPC has a higher head capacity than motor pump MPD (i.e., D1C > D1D). Motor pump MPD has a higher flow capacity than motor pump MPC (i.e., B2D > B2C).

[0169] This explains the relationship between motor pump MPB and motor pump MPD. Motor pump MPD has a larger motor capacity than motor pump MPB (i.e., LgD > LgB). Motor pump MPD has a higher flow rate capacity than motor pump MPB (i.e., B2D > B2B). Motor pump MPB has the same head capacity as motor pump MPD (i.e., D1B = D1D).

[0170] As shown in Figure 30, the inner diameter D2 and outer diameter D3 of the stator casing 20 are the same for all motor pumps MP. Therefore, operators can prepare components of different sizes according to the head capacity and flow rate capacity, and select the optimal component from among multiple components based on the operating conditions of the motor pump MP.

[0171] By making the inner diameter D2 and outer diameter D3 of the stator casing 20 the same, the pump unit PU can easily change its performance without changing the size of components that do not depend on the head capacity or flow rate capacity (e.g., bearing 5, suction casing 21, and discharge casing 22).

[0172] Figure 31A is a cross-sectional view of a motor pump according to another embodiment, and Figure 31B is a view of the motor pump shown in Figure 31A from the axial direction. As shown in Figures 31A and 31B, the motor pump MP may be equipped with a swivel stopper (in other words, a foul stop) 130 located on the rear side of the impeller 1.

[0173] In the embodiment shown in Figure 31B, one swirl stopper 130 is provided, but at least one swirl stopper 130 may be provided. The swirl stopper 130 is fixed to the discharge casing 22 and faces the main plate 10 of the impeller 1. The swirl stopper 130 can prevent the handling fluid discharged from the impeller 1 from swirling between the impeller 1 and the discharge casing 22.

[0174] Figure 32A is a cross-sectional view of a motor pump according to another embodiment, and Figure 32B is a front view of the suction casing of the motor pump shown in Figure 32A. As shown in Figures 32A and 32B, the motor pump MP comprises a suction casing 141 and a discharge casing 142 having a flat flange shape.

[0175] In the embodiments described above, the suction port 21a of the suction casing 21 protrudes from the outer surface of the suction casing 21, and similarly, the discharge port 22a of the discharge casing 22 protrudes from the outer surface of the discharge casing 22. In this embodiment, since the suction casing 141 has a flat flange shape, the suction port 141a is formed on the same plane as the outer surface of the suction casing 141. Similarly, since the discharge casing 142 has a flat flange shape, the discharge port 142a is formed on the same plane as the outer surface of the discharge casing 142.

[0176] This structure allows the connecting pipe 140, which is connected to the motor pump MP, to be directly connected to the suction casing 141. Although not shown, the connecting pipe 140 may also be directly connected to the discharge casing 142, which has a flat flange shape.

[0177] This configuration eliminates the need to arrange connecting members (connecting members) for linking the connecting pipe 140 and the suction casing 141, thereby reducing the number of parts required to connect the piping (not shown) to the motor pump MP.

[0178] Since the connecting member is a component from which liquid leakage is expected, eliminating the connecting member can reliably prevent liquid leakage. In this embodiment, although not shown, a sealing member (for example, an O-ring or gasket) is placed between the connecting pipe 140 and the suction casing 141.

[0179] An insertion hole 141b is formed on the radially outer side of the suction port 141a of the suction casing 141, into which a fastener 150 for fastening the connecting pipe 140 and the suction casing 141 is inserted. The connecting pipe 140 has a through hole 140a that communicates with the insertion hole 141b. By inserting the fastener 150 into the through hole 140a and the insertion hole 141b, the worker can fasten the connecting pipe 140 and the suction casing 141 together.

[0180] A bolt housing portion 142b is formed on the radially outer side of the discharge port 142a of the discharge casing 142 to accommodate the head 25a of the through bolt 25. By housing the head 25a of the through bolt 25 in the bolt housing portion 142b, it is possible to prevent the head 25a from protruding from the discharge casing 22.

[0181] In one embodiment, the suction casing 141 may have a bolt housing portion corresponding to the bolt housing portion 142b. That is, at least one of the suction casing 141 and the discharge casing 142 has a bolt housing portion for housing the head 25a of the through bolt 25.

[0182] Figure 33 shows a pump unit equipped with a motor pump connected in series. As shown in Figure 33, the motor pump MP shown in Figures 32A and 32B is equipped with a suction casing 141 and a discharge casing 142 having a flat flange shape, so that the suction casing 141 and the discharge casing 142, which are positioned adjacent to each other, can make surface contact with each other. The suction casing 141 and the discharge casing 142 that are in surface contact with each other correspond to an intermediate casing.

[0183] Although not shown in the diagram, a sealing member (e.g., an O-ring or gasket) is placed between the suction casing 141 and the discharge casing 142, which are in surface contact with each other.

[0184] According to this embodiment, there is no need to arrange an intermediate casing 61 (see Figure 10), and a pump unit PU equipped with multiple motor pumps MP can be configured by simply connecting multiple motor pumps MP having the same structure directly in series.

[0185] The motor pump MP according to this embodiment has simple main components (i.e., an impeller 1, a rotor 2 and a stator 3, and a bearing 5), and is small and lightweight. Therefore, by using through bolts 25, multiple motor pump MPs arranged in series can be easily fastened together as a single unit.

[0186] Furthermore, by bringing the suction casing 141 and the discharge casing 142 into surface contact with each other, the thermal conductivity of the pump unit PU can be improved, and temperature equilibrium can be achieved among the multiple motor pumps MP. As a result, the pump unit PU can be operated stably.

[0187] Figure 34 shows another embodiment of the impeller. In the embodiment described above, the impeller 1 is a centrifugal impeller. More specifically, the impeller 1 has a main plate 10 extending perpendicular to the centerline CL direction, and the liquid pressurized by the impeller 1 is discharged perpendicular to the centerline CL. In the embodiment shown in Figure 34, the impeller 1 is a diagonal flow impeller. More specifically, the impeller 1 has a main plate 160 inclined at a predetermined angle with respect to the centerline CL direction. The main plate 160 is inclined from the suction side to the discharge side, and the liquid pressurized by the impeller 1 is discharged diagonally outward with respect to the centerline CL.

[0188] Figure 35 shows another embodiment of the motor pump. In the embodiment shown in Figure 35, the motor pump MP comprises a discharge casing 22 having a discharge port 322 extending vertically perpendicular to the centerline CL direction of the motor pump MP. The discharge port 322 has an outlet 322a that opens upward, and the suction port 21a and the discharge port 322a are orthogonal to each other.

[0189] In the embodiment shown in Figure 35, the motor pump MP is a so-called end-top type motor pump in which the suction port 21a and discharge port 322a are perpendicular to each other. Such a motor pump MP has a compact structure. For example, depending on the installation environment of the motor pump MP, it may not be possible to install a motor pump MP with a structure in which the suction port 21a and discharge port 22a are arranged in a straight line. Even in such cases, an end-top type motor pump MP can be installed. Thus, in this embodiment, the motor pump MP can be installed in a variety of installation environments.

[0190] As shown in Figure 35, the motor pump MP may further include a side plate 300 that restricts the outflow of the liquid (handled liquid) pressurized by the impeller 1 to the discharge port 322. In the embodiment shown in Figure 35, the side plate 300 has a disc shape and is fixed to the return vane 30.

[0191] The side plate 300 is positioned between the main plate 10 and the return blade 30 of the impeller 1. A portion of the liquid pressurized by the impeller 1 flows through the gap between the side plate 300 and the discharge casing 22 via the return blade 30 to the discharge port 322 and is discharged from the discharge opening 322a. The other portion of the liquid pressurized by the impeller 1 flows into the gap between the side plate 300 and the main plate 10 of the impeller 1.

[0192] When impeller 1 rotates, a fluid force (i.e., hydrodynamic force) acts on impeller 1, pushing it toward the discharge casing 22. The flow of liquid that has entered the gap between the side plate 300 and the main plate 10 is restricted by the side plate 300, so the pressurized liquid remains in the gap between the side plate 300 and the main plate 10. The liquid remaining in the gap between the side plate 300 and the main plate 10 absorbs the hydrodynamic force acting on impeller 1, thus restricting the movement of impeller 1 toward the discharge casing 22.

[0193] When the motor pump MP is in steady operation, a thrust force acts on the impeller 1 from the discharge casing 22 side to the suction casing 21 side. Therefore, even when fluid forces act on the impeller 1, the impeller 1 is stably held in place by the bearing 5.

[0194] Figure 36 shows a side plate provided on the motor pump according to the above-described embodiment. As shown in Figure 36, the side plate 300 is applicable not only to the end-top type motor pump but also to the motor pump MP according to the above-described embodiment.

[0195] Figure 37 shows another embodiment of the side plate. As shown in Figure 37, the side plate 300 may have an opening 300a formed in its center. As described above, liquid that flows into the gap between the side plate 300 and the main plate 10 may remain in the gap between the side plate 300 and the main plate 10.

[0196] In this case, the rotation of the impeller 1 causes the stagnant liquid to swirl, and eventually, there is a risk of it generating heat. By forming the opening 300a in the side plate 300, a circulating flow of liquid is formed between the gap between the side plate 300 and the discharge casing 22, and between the side plate 300 and the impeller 1. Therefore, the liquid present between the side plate 300 and the impeller 1 flows into the discharge casing 22, preventing the liquid from generating heat and maintaining a constant liquid temperature. Furthermore, the opening 300a can also serve to discharge air contained in the stagnant liquid into the discharge casing 22.

[0197] In the embodiment shown in Figure 37, the opening 300a of the side plate 300 is a single opening formed on the center line CL, but the number of openings 300a is not limited to this embodiment. The side plate 300 may have multiple openings 300a to the extent that it restricts the movement of the impeller 1 toward the discharge casing 22 side.

[0198] Furthermore, the opening 300a does not necessarily have to be formed on the center line CL, as long as it can form a circulating flow of liquid. For example, the side plate 300 may have at least one opening 300a arranged concentrically around the center line CL.

[0199] The shape of the opening 300a is not particularly limited and may be circular or polygonal (for example, triangular or quadrilateral). Similarly, the size (i.e., area) of the opening 300a is not particularly limited, to the extent that the side plate 300 restricts movement toward the discharge casing 22.

[0200] The embodiments described above are intended to enable persons with ordinary skill in the art to implement the present invention. Various modifications of the above embodiments can be made naturally by those skilled in the art, and the technical idea of ​​the present invention can be applied to other embodiments as well. Therefore, the present invention is not limited to the embodiments described, but is to be interpreted in the broadest sense according to the technical idea defined by the claims. [Industrial applicability]

[0201] The present invention can be used for motor pumps, pump units, and methods for balancing the impeller of a motor pump. [Explanation of Symbols]

[0202] 1,1A,1B,1C Impeller 2 rotors 2a Iron core 2b Magnet 3 Stator 5 bearings 6 Rotating side bearing body 6a Cylindrical section 6b Flange section 7 Fixed side bearing body 7a Cylindrical section 7b Flange section 10 Main plate 10a Through hole 11 Side panel 11a Outer edge 12 wings 15 Suction section 16 Main body 17 Protrusion 17a Outer surface 17b Inner surface 20 Stator casing 20a Inner surface 21 Suction casing 21a Inlet 22 Discharge casing 22a Discharge port 25 Through bolts 25a head 30 Return Feathers 31 sealing member 32,33 Sealing member 40,41,42 groove 41a Both ends 45 Load reduction structure 46 Back Wing 47 Notches 50,51 Slope 53,54 Slope 60 Inverters 61 Intermediate casing 65 Piping 70, 70A, 70B protrusions 71 Tip 75. Balance adjustment jig (center support adjustment jig) 76 Axis 77 Fixed body 80 Center Cap 85. Balance adjustment jig (edge ​​support adjustment jig) 86 Supporters 87 Shaft 90 Weight insertion holes 91 weights 100 Control device 100a Signal receiving unit 100b storage section 100c Control Unit 101 Current Sensor 102 Terminal block 105 Power lines 106 signal line 107 Protective Cover 108 Copper Bars 110 cover 117 Protrusion 118 Mounting part 120 sealing member 121 Sealing member 125 Intermediate casing 126 Communication shaft 127A Sealing material 127B Sealing component 128 Discharge side bearing 129 Channels 130 Swivel stop 140 connecting pipes 141 Suction casing 141a Inlet 141b Insertion hole 142 Discharge casing 142a Discharge port 142b Bolt housing 150 fasteners 160 Main plate 300 Side Plate 300a aperture 322 Discharge Ports 322a Discharge port MP Motor Pump PU Pump Unit CL center line Ra suction side region Rb discharge side area Rc intermediate area RS Rotation Axis Nt Nut

Claims

1. Multiple motor pumps, The system includes a control device for operating the plurality of motor pumps at a variable speed, Each of the aforementioned multiple motor pumps is The impeller and A rotor fixed to the impeller, A stator positioned radially outward from the rotor, The impeller is supported by a bearing located outside the flow path of the impeller, The rotor and bearing are located in the suction-side region of the impeller in a pump unit.

2. The aforementioned multiple motor pumps are connected in series, The control device is Based on the assumed current value expected during normal operation of the motor pump, the lower limit current value is calculated. The measured current value of the motor pump during current operation is compared with the lower limit current value. The pump unit according to claim 1, wherein if the measured current value is lower than the lower limit current value, it is determined that an abnormality has occurred in at least one of the plurality of motor pumps.

3. The pump unit according to claim 2, wherein the measured current value corresponds to the starting current value at the time of starting the motor pump.

4. The pump unit according to claim 2, wherein the measured current value corresponds to the operating current value during steady-state operation of the motor pump.

5. The pump unit according to claim 214, wherein the control device determines the assumed current value based on at least one of the rated current value and the allowable current value of the motor pump.

6. The pump unit according to claim 4, wherein the control device determines the assumed current value based on the flow rate on the discharge side of the motor pump.

7. The pump unit according to claim 4, wherein the control device determines the assumed current value based on the pressure on the discharge side of the motor pump.

8. The pump unit according to any one of claims 2 to 7, wherein the lower limit current value is determined based on the number of the plurality of motor pumps.

9. The aforementioned multiple motor pumps are connected in parallel. The pump unit according to claim 1, wherein the control device is configured to stagger the startup timing of each of the plurality of motor pumps.

10. The pump unit according to claim 9, wherein the control device starts one of the plurality of motor pumps, and then starts a motor pump adjacent to the started motor pump.

11. Multiple impellers of different sizes, Multiple rotors fixed to the aforementioned multiple impellers and having different lengths, A plurality of stators having lengths corresponding to the lengths of the plurality of rotors, A plurality of stator casings that house the plurality of stators and have a length corresponding to the length of the plurality of stators, The system comprises bearings that support each of the aforementioned plurality of impellers, A motor pump in which each of the plurality of rotors and the bearings are located in the suction-side region of each of the plurality of impellers.

12. The motor pump according to claim 11, wherein the plurality of impellers comprises a plurality of side plates having the same diameter and a plurality of main plates having different diameters.

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