underwater pump motor

Abstract

Underwater pump motor with PM line start technology - a rotating field stand, - a runner, - a runner wave (2), and - a rotor lamination package (3) comprising at least one rotor lamination (4) and arranged circumferentially on the rotor shaft (2), where the diameter of the rotor shaft (2) is equal to or greater than 45% of the diameter of the rotor (1), the rotor plate (4) has at least two axially extending magnet pockets (7) which serve to receive a permanent magnet (8), and a pole gap recess (10) between these magnet pockets (7), the pole gap recess (10) between the magnetic pockets (7) and the recess (5) for receiving a profile bar (6) form an interconnected common composite recess (13), and the composite recess (13) includes both an area for the poll gap recess (10) and an area for the recess (5) for receiving the profile bar (6), so that the composite recess (13) is only partially filled by an inserted profile bar.

Description

[0001] The present invention relates to an underwater pump motor in PM line start technology with a rotating field stator, a rotor, a rotor shaft, and a rotor laminated core, which comprises at least one rotor laminate and is arranged circumferentially on the rotor shaft, wherein the diameter of the rotor shaft is equal to or greater than 45% of the diameter of the rotor, the rotor laminate has at least two axially extending magnet pockets which serve to receive a permanent magnet, and a pole gap recess between these magnet pockets, and the pole gap recess between the magnet pockets and the recess for receiving a profile bar form an interconnected common composite recess.

[0002] Submersible motor pumps, also known as U-shaped motor pumps, are used, for example, as borehole pumps for the extraction of drinking water and for dewatering mining facilities. The power range of U-shaped motor pumps starts below one kilowatt and extends into the megawatt range. Due to the usually limiting borehole diameter, submersible motor pumps must be slim in design so that they can be inserted into the borehole. Typically, a centrifugal pump is rigidly coupled to the pump motor and mounted above the pump motor. The fluid to be pumped flows along the housing of the pump motor, cooling it in the process.

[0003] The standard drive for submersible motor pumps remains the squirrel-cage motor. An important development goal for submersible motor pumps is increasing energy efficiency. In addition to potentially improving this efficiency through the transition to variable-speed process control, it is first necessary to increase the efficiency of the individual drive components.

[0004] However, in some cases, it is not possible to sufficiently improve energy efficiency with the help of a variable-speed pump drive. Therefore, in such applications, a pump powered by a fixed three-phase power grid will continue to be used in the future.

[0005] Since the operating principle of the asynchronous motor, whose speed can be varied using a frequency converter, involves the existence of heat losses in the squirrel-cage rotor, the possibilities for increasing efficiency are physically limited. Therefore, the transition to PM synchronous technology, which must also enable line-start operation, is a next step in innovation.

[0006] The design of such a submersible pump motor using PM line start technology basically includes a rotating field stator and a rotor, which, in addition to the permanent magnets, must also have a starting cage. It is therefore a hybrid rotor with the functional components of a squirrel cage rotor and a PM rotor.

[0007] WO 2013 / 054301 A2 discloses an LSMP motor for a submersible pump, comprising a rotor with a radially outer region and a radially inner region. The radially outer region includes recesses for receiving bars of a squirrel cage, and the radially inner region includes recesses for receiving magnets.

[0008] EP 2 132 863 B1 discloses a synchronous motor which starts automatically on the three-phase network, whereby the magnets embedded in the laminated core are to be positioned as close as possible to the rotor shaft.

[0009] US 2002 / 0 140 311 A1 describes the rotor of a synchronous motor which is intended to improve the performance of the motor as well as a manufacturing method for such a motor.

[0010] From DE 103 59 159 A1 an underwater asynchronous motor is known which is intended to provide a significant increase in power for a given motor diameter without loss of mechanical stability, whereby the motor has at least two stator and rotor sections.

[0011] JP 2003 - 189 518 A describes a cage rotor and a synchronous induction motor using the cage rotor, wherein the cage rotor is said to be able to improve the synchronization torque and eliminate abnormal phenomena in the starting torque characteristics.

[0012] Due to the very slim design, which is advantageous for the preferred application area, the starting cage and the permanent magnets compete for the small volume of the active rotor part available in the design.

[0013] The present invention discloses a rotor with which an electric motor with a very slim design can be implemented.

[0014] Since a slim design is advantageous for submersible pump motors due to their potential use in a borehole, "slimness" (= ratio of lamination stack length to lamination stack diameter) is necessary. Achieving this requires particular challenges in developing a rotor suitable for this application. Reducing the lamination stack height can be considered a primary goal.

[0015] The rotor having the features of claim 1 solves the problems arising from the prior art.

[0016] Accordingly, the composite recess comprises both an area for the pole gap recess and an area for the recess for receiving the profile bar, so that the composite recess is only partially filled by an inserted profile bar.

[0017] Preferably, the rotor diameter is chosen to be the largest diameter of the rotor that occurs during rotation around the rotor's axis of rotation. The rotor shaft diameter is preferably chosen to be the largest diameter of the rotor shaft that occurs during rotation around the rotor shaft's axis of rotation. It will be clear to a person skilled in the art that, in a rotor according to the invention, the axes of rotation of the rotor shaft and the rotor are identical.

[0018] Preferably, the rotor has a symmetrical structure, which, in an optional embodiment, is rotationally symmetrical when rotated by an angle less than or equal to 180° around its rotation axis. Thus, if the rotor is rotated around its rotation axis by an angle less than or equal to 180°, there is an angle at which the rotor is identical to its non-rotated appearance.

[0019] According to a further development of the invention, the rotor core has at least one axially extending recess for receiving a profile bar to form parts of a starting cage. These recesses are also referred to as profile bar recesses. Typically, the profile bars inserted into the recesses are electrically connected at their respective end faces to a short-circuit ring, e.g., by soldering or welding, to create a starting cage.

[0020] According to a further modification of the invention, the rotor comprises profile bars, preferably profile bars made of copper, which are arranged in the profile bar recesses and form components of a starting cage. It is particularly advantageous if the profile bars inserted into the profile bar recesses are prefabricated profile bars.

[0021] Due to the high slenderness of the rotor according to the invention, the die-casting process used in the prior art for producing profile bars in designated recesses is not available. The pressures used in this case when injecting the molten metal would lead to the destruction or damage of the rotor core, which is particularly thin in its laminated core height. This is due to the fact that the diameter of the rotor shaft is equal to or greater than 45%, preferably equal to or greater than 50%, of the rotor diameter, and the stability due to the slim design is not suitable for the die-casting process.

[0022] In addition, there is the problem that the aluminum melt cools down too early in long sheet packages, resulting in voids and bar breaks during die casting.

[0023] Prefabricated profile bars, on the other hand, can be inserted into the profile bar recesses and are the only sensible alternative for such slim runners.

[0024] According to a further optional development of the invention, the profile bars that partially form the thrust cage are identical in their cross-sectional shape. Thus, all profile bars have a common bar profile. This is advantageous because it allows for simple production of the profile bars and eliminates the need to pay attention to the shape of the profile bar recesses when inserting the profile bars. Accordingly, it is advantageous if all profile bar recesses are designed accordingly in their cross-sectional area.

[0025] Preferably, the starting cage is rotationally symmetrical with respect to a rotation about its axis of rotation at an angle α, where α is the division of 360° by the number of profile bar recesses. The rotation axis of the starting cage is identical to the rotation axis of the rotor. This means that a starting cage comprising, for example, 36 profile bars is rotationally symmetrical with respect to a rotation of 10° around the rotation axis.

[0026] The use of a single bar profile and the symmetrical design of the starting cage result in rotor symmetry, which has the significant advantage of eliminating disruptive oscillation torques of twice the slip frequency during the motor's run-up phase. This prevents the excitation of eigenmodes during run-up.

[0027] According to the invention, the rotor lamination has at least two axially extending magnetic pockets, which serve to accommodate a permanent magnet, and an optional pole gap recess between these magnetic pockets. Preferably, the rotor lamination has more than two magnetic pockets. As a rule, the number of magnetic pockets corresponds to the number of poles of the motor. The magnetic pockets run essentially parallel to the rotor's axis of rotation. According to a further development of the invention, the rotor lamination has a further recess, the so-called pole gap recess, between the magnetic pockets, i.e., in the same radial area as the magnetic pockets themselves.

[0028] If permanent magnets are inserted into the designated magnetic pockets, the pole gap recess between the magnetic pockets and the permanent magnets ensures that a large portion of the magnetic flux is not short-circuited directly in the rotor core. Instead, a large portion of the magnetic flux takes the path through the air gap into the stator, thus minimizing the disruptive stray flux in the rotor.

[0029] It is advantageous if the pole gap recess between the magnetic pockets extends over at least the same or the same radial area as the magnetic pockets. This makes it difficult for magnetic field lines from different magnetic poles to directly close through the rotor lamination.

[0030] According to the invention, the pole gap recess between the magnet pockets and the recess for accommodating a profile bar (= profile bar recess) form a mutually connected composite recess. According to the invention, the composite recess comprises both the area for the pole gap recess and the area for the profile bar recess. This further reduces the stray flux that develops between the poles of a magnet in the rotor lamination.

[0031] The composite recess is thus designed to accommodate a profile bar without being completely or almost completely filled by the profile bar. According to the invention, the composite recess is therefore only partially filled by the profile bar when inserted.

[0032] The composite recess preferably has positioning ribs that indicate a demarcation between the pole gap recess and the recess for receiving a profile bar. The positioning ribs preferably help facilitate the insertion of a profile bar, preferably a prefabricated profile bar, into the composite recess. Preferably, there are exactly two positioning ribs per composite recess, which are aligned with each other in a cross-sectional view of the rotor. The positioning ribs can be positioned opposite each other, so that an imaginary extension of the two ribs would result in a straight line.

[0033] Permanent magnets are present in the magnetic pockets, which in a particularly advantageous embodiment of the invention are rare earth magnets.

[0034] According to a further advantageous embodiment of the invention, the rotor shaft is made of a ferromagnetic material. This makes it possible to incorporate the rotor shaft into the flux guide of the permanent magnets. This, in turn, allows the area of ​​the rotor lamination below the magnetic pockets to be reduced. This contributes to a lower overall lamination stack height.

[0035] The rotor core of the rotor according to the invention is preferably bonded with a bonding varnish. The bonding varnish on the rotor core structurally protects the magnets in the magnet pockets from corrosion. Corrosion protection of the magnets' front surfaces can be achieved by encapsulating or bonding the magnets with a low-viscosity resin after they have been inserted into the magnet pockets. This requires that the dimensions of the magnet to be inserted into the magnet pocket be a few tenths of a millimeter smaller than the space provided by the magnet pocket.

[0036] As an example of a slenderness ratio achievable with the invention, a rotor outer diameter of 71 mm, a shaft diameter of 37 mm, and a laminated core length of 800 mm are assumed. This results in a slenderness ratio of approximately 11.3.

[0037] Further advantages and features of the invention will become clear from the exemplary embodiments discussed in more detail in the figures. They show: Fig. 1: a longitudinal section of a water-filled underwater pump motor with the rotor according to the invention, Fig. 2: a schematic diagram of a non-claimed embodiment of a rotor in the unwound state, Fig. 3: a detailed view of the rotor plate of a non-claimed embodiment of a rotor, and Fig. 4: a detailed representation of the rotor according to the invention according to an embodiment of the invention.

[0038] Fig. Figure 1 shows a water-filled submersible pump motor 20 in longitudinal section. The rotor 1, the rotor core 3, and the rotor shaft 2 are visible. The rotor shaft is connected to a pump (not shown) for pumping water. The pump motor 20 further comprises a housing 23 that surrounds a stator 21 and the rotor 1. A liquid 24, in this case water, is present between the stator 21 and the rotor 1, so that the stator 21 and the rotor 1 are completely immersed. The liquid 24 is preferably water enriched with antifreeze.

[0039] Fig. Figure 2 shows a schematic diagram of the rotor concept in an unwound state. In the unwound state, the rotor lamination 4, which is normally bent around the rotor shaft with a circular cross-section, and the permanent magnets 8 are wound, i.e., shown along a straight line.

[0040] This figure only shows the rotor lamination 4 to be wound around the rotor shaft 2. The straight edge 9 closest to the permanent magnet 8 is brought into contact with the rotor shaft 2. It can be seen that the permanent magnets 8 are separated by a pole gap recess 10 in the space separating them. While this pole gap recess 10 does not completely prevent the magnetic field lines from closing through the rotor lamination, it does restrict the magnetic flux so that it is largely closed around the pole gap recess 10. Since the regions 11 (= lower web) located radially closer to the rotor's rotational axis and the region 12 (= upper web) located further away from it, which are located above and below the pole gap recess, are thin and thus highly saturated, they limit the leakage flux through the rotor lamination 4.Also visible are the profile bars 6, whose bar profile is only indicated as a circle or trapezoid for illustrative purposes. The profile bar 6 is inserted into a recess 5 provided for receiving a profile bar 6.

[0041] Fig. Figure 3 shows a detailed view of a transition area between two adjacent permanent magnets 8. These are inserted into recesses 7 provided for this purpose, so-called magnetic pockets. The pole gap 10 arranged between the adjacent magnetic pockets 7 can be seen, above which a recess 5 provided for the profile bar 6 is provided. Above here means the area further away in the radial direction from the axis of rotation of the rotor lamination 4 or the rotor 1. Between the pole gap recess 10 and the profile bar recess 5 there is a web 12 that separates the pole gap recess 10 from the profile bar recess 5. Furthermore, the magnetic pocket of the rotor lamination 4 is not directly connected to the rotor shaft 2, but is spaced apart from it.

[0042] Fig. 4 shows a similar representation as Fig. 3, however, in the Fig.In the embodiment shown in Figure 4, the web 12, which separates the pole gap recess 10 from the profile bar recess 5, is not continuous. Therefore, a composite recess 13 comprising the pole gap recess 10 and the profile bar recess 5 is now created. To facilitate insertion of the preferably prefabricated profile bar 6 into the area provided for this purpose, positioning webs 14 are provided, which indicate a separation of the previously separate pole gap recess 10 and profile bar recess 5. The omission of the web further reduces the stray flux occurring between the various poles of the permanent magnets and thus contributes to a particularly effective rotor. The provision of a composite recess 13 is only possible because the profile bar 6 is prefabricated and can be inserted into the corresponding recess 5.The die-casting process conventionally used in the prior art cannot be applied due to the connection between the two recesses 10 and 5 and the insufficient height of the laminated core. This results in a particularly advantageous rotor for an electric motor, which can achieve a particularly advantageous slenderness ratio.

Claims

[1] Submersible pump motor in PM-Line-Start technology with - a rotating field stator, - a runner, - a rotor shaft (2), and - a rotor core (3) comprising at least one rotor core (4) and arranged circumferentially on the rotor shaft (2), where the diameter of the rotor shaft (2) is equal to or greater than 45% of the diameter of the rotor (1), the rotor plate (4) has at least two axially extending magnetic pockets (7) which serve to receive a permanent magnet (8), and a pole gap recess (10) between these magnetic pockets (7), the pole gap recess (10) between the magnet pockets (7) and the recess (5) for receiving a profile bar (6) form a mutually connected common composite recess (13), and the composite recess (13) comprises both an area for the pole gap recess (10) and an area for the recess (5) for receiving the profile bar (6), so that the composite recess (13) is only partially filled by a profile bar when it is inserted. [2] Submersible pump motor according to claim 1, wherein the rotor (1) has a symmetrical structure, wherein preferably the rotor (1) is rotationally symmetrical about its axis of rotation with an angle less than or equal to 180°. [3] Underwater pump motor according to one of the preceding claims, wherein the rotor core (3) has at least one recess (5) extending in the axial direction for receiving a profile bar (6) in order to form a starting cage. [4] Submersible pump motor according to claim 3, further comprising profile bars (6), preferably profile bars (6) made of copper, which are arranged in the recesses (5) and form elements of a starting cage, wherein the profile bars (6) are preferably prefabricated profile bars (6). [5] Underwater pump motor according to claim 4, wherein the profile bars (6) partially forming the starting cage are identical in their cross-sectional shape, i.e. have a common bar profile. [6] Submersible pump motor according to claim 4 or 5, wherein the starting cage is rotationally symmetrical to a rotation about its axis of rotation with the angle α, where α = 360° / number of recesses (5) for receiving profile bars (6). [7] Underwater pump motor according to one of the preceding claims 1 to 6, wherein the pole gap recess (10) between the magnet pockets (7) extends over at least the same or the same radial area as the magnet pockets (7). [8] Underwater pump motor according to one of claims 1 to 7, wherein the composite recess (13) has positioning webs (14) which indicate a demarcation of the pole gap recess (10) from the recess (5) for receiving a profile bar (6), wherein the positioning webs (14) are preferably designed to facilitate insertion of a profile bar (6) into the composite recess (10). [9] Underwater pump motor according to one of claims 1 to 8, wherein permanent magnets (8), preferably rare earth magnets, are present in the magnet pockets (7). [10] Underwater pump motor according to one of the preceding claims, wherein the rotor shaft (2) is made of ferromagnetic material. [11] Underwater pump motor according to one of the preceding claims, wherein the rotor core (3) is packaged by means of a baking varnish.

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