Stator sheet of a submersible electric motor

Abstract

The utility model relates to the field of electrical engineering in the oil producing industry, and more specifically to the design of a stator for an oil-filled submersible electric motor for driving centrifugal pumps in oil production. The technical result consists in increasing the slot fill factor with winding wire to 0.73-0.75, which provides the possibility of increasing the electric motor power by 10% within the dimensions of a 105 mm magnetic circuit sheet; using a standardized winding wire of the same diameter and the same number of turns for electric motors of different rated power within a standard size range; reducing the level of higher harmonics, which leads to an improvement in the vibroacoustic characteristics of valve electric motors (reduced noise and vibration, reduced torque pulsations).The technical result is achieved in that the stator magnetic circuit sheet contains 36 closed identical slots formed by two parallel straight lines (long sides) and two semicircular arcs (short end sides), facing the outer surface of the sheet and the bore, respectively. The radius of the semicircle (R) is equal to half the slot width, and the ratio of the slot height (h) to its width (b) is from 3.5 to 4.0. 6 z.p. f-y. 2 ill.

Description

[0001] This utility model relates to electrical engineering in the oil production industry, specifically to the design of active components (magnetic cores) of a submersible electric motor (SEM) used to drive centrifugal pumps in units for the mechanized extraction of formation fluids (oil, water, gas-liquid mixtures) from oil and water wells. The utility model can be applied in the design and production of asynchronous and synchronous electric motors with permanent magnets, with a stator magnetic core outer diameter of 105 mm.

[0002] SPEED motors operate under extreme conditions of limited production casing diameters and high pressure and temperature of the formation fluid. The primary way to increase motor power within a given size is to improve the efficiency of the stator's internal volume, primarily by increasing the copper slot fill factor and optimizing the magnetic circuit.

[0003] The slot fill factor (kz) is defined as the ratio of the total copper cross-sectional area to the slot cross-sectional area minus the area of ​​the slot insulation. This is a critical parameter, as it directly determines how much copper can be placed in the motor. A higher slot fill factor results in higher specific power with the same motor dimensions, improved electromagnetic characteristics, reduced electrical resistance and copper losses, and a smaller motor size with the same output power, resulting in higher efficiency. Traditional winding methods (random winding with round wire) typically provide a slot fill factor of approximately 0.5. For example, patent RU2859065C1 (IPC H02K21 / 14, H02K1 / 276, priority 03.07.2025) describes a synchronous electric machine with permanent magnets, the stator of which has a copper slot filling factor of 0.49.

[0004] Patent RU2754498C1 (IPC H02K15 / 085, H02K1 / 16, H02K3 / 48, priority date: 23.11.2020) increases the slot fill factor by improving the manufacturing process of the slot insulation. U-shaped grooves are inserted into the magnetic circuit slots, with the U-shaped groove walls spaced apart from the slot walls. A polymer coating is uniformly distributed under pressure into the space between the U-shaped groove walls and the magnetic circuit slot, forming an insulating layer.

[0005] Modern technologies are aimed at forming the winding wire so that it precisely matches the shape of the groove, but there are still difficulties with round cross-section wires, which leave significant gaps.

[0006] Various designs of stators for submersible motors are known. Traditionally, for motors with an outer diameter of 105 mm, sheets of electrical steel with 18 or 24 slots are used (CN203352306U, IPC H02K1 / 14, H02K1 / 24, priority dated 01.07.2013). Such technical characteristics of submersible motor series are described in the solutions produced by such manufacturers as Novomet, Borets, etc. The submersible motor described in patent RU2516472C2 (IPC H02K5 / 16, H02K1 / 16, H02K1 / 27, H02K21 / 12, priority dated 08.02.2011) contains a stator with a toothed magnetic circuit and a rotor located inside it. The stator contains 24 closed slots for laying the winding cable, and on the inner surface of the stator teeth in the axial direction there are technological slots (protrusions) evenly spaced around the circumference, the number of which is equal to three, or a multiple of three.This stator design reduces vibration and improves the starting properties of the PED, and allows for an increase in the number of winding conductors in the slot; however, it does not solve the problem of winding standardization for a range of motors.

[0007] A known stator for a submersible motor comprises a cylindrical housing and a laminated magnetic core installed within it. The outer surface of the core has longitudinal slots (patent RU107416U1, IPC H02K1 / 18, priority dated March 11, 2011). In this solution, the slots and tenons on the outer surface serve to mechanically secure the steel bundle within the housing and prevent it from rotating. However, the design of the internal bore and the number of slots within it are not optimized to maximize the filler wire capacity.

[0008] A PSM stator with a large length-to-diameter ratio is also known (patent RU2336619C1, IPC H02K1 / 18, H02K1 / 12, H02K5 / 132, priority dated December 18, 2006). In this stator, symmetrical longitudinal slots are made on the outer surface of the magnetic circuit along the radial axes of the teeth to increase the rigidity of the structure. This solution is aimed at solving the problem of mechanical strength and alignment of a long rotor, but does not address issues of optimizing the slot geometry for winding placement.

[0009] The disadvantages of these solutions include the lack of a stator sheet geometry for a motor with a stator outer diameter of 105 mm that simultaneously ensures the maximum slot fill factor, standardized winding data, and optimal harmonic field composition for electric motors. For motors with a stator outer diameter of 105 mm, the number of stator slots is typically 18 or 24, and the slot shape and size do not allow for the installation of round winding wires with minimal voids. The fill factor of such stator slots with copper winding wire does not exceed 0.59-0.61. This limits motor power. The lack of standardized winding data means that to produce motors with different power ratings, manufacturers are forced to use wires of different cross-sections and different numbers of turns, which complicates production and repair.Suboptimal harmonic composition of the field for electric motors does not allow minimizing higher harmonics, which leads to increased vibrations and reduced efficiency.

[0010] In addition, the designs of known technical solutions lack a set of features that ensure the simultaneous:

[0011] increasing the filling coefficient of the grooves with round wire;

[0012] reducing the volume of unfilled space in the groove;

[0013] formation of integer winding structure;

[0014] unification of winding data for a range of electric motors;

[0015] reduction of higher spatial harmonics of the magnetic field.

[0016] However, known solutions do not provide for the coordination of the groove geometry with the diameter of the round winding wire, based on the condition of their orderly laying.

[0017] The technical objective of the utility model is to create a stator sheet geometry for a submersible electric motor with an outer diameter of 105 mm, which allows increasing the slot fill factor with winding wire to 0.73-0.75, which leads to an increase in the electric motor power by 10%, unification of production due to the use of winding wire of the same diameter and the same number of turns for electric motors of different rated power within a standard size range and a decrease in the level of higher harmonics, which leads to an improvement in the vibroacoustic characteristics of valve electric motors (reduction of noise and vibration), including the reduction of torque pulsations.

[0018] To solve the stated problem, a sheet of the magnetic circuit of the stator of a submersible electric motor for driving an electric centrifugal pump is proposed, containing teeth, grooves for laying the winding wire, made for an electric motor with an outer diameter of the stator of 105 mm and containing 36 closed identical grooves formed by two parallel straight lines (long sides) and two arcs of semicircles (short end sides), facing respectively to the outer surface of the sheet and to the bore, wherein the radius of the semicircle (R) is equal to half the width of the groove, and the ratio of the height (h) of the groove to its width (b) is from 3.5 to 4.0.

[0019] The following definitions are used in the text below:

[0020] The width (b) of a groove is defined as the smallest distance between the parallel long sides of the groove.

[0021] The height (h) of a groove is defined as the greatest distance between the arcs of the semicircles from which the short end sides of the groove are formed.

[0022] The radius of the semicircle (R) is defined as the radius of the arc of the semicircles that form the short end sides of the groove; geometrically, it represents the distance from the center of the specified semicircle to its arc and, based on the typical configuration of the groove, is taken to be equal to half the width of the groove: R=b / 2.

[0023] Inner bore (diameter) of stator sheet (D ВН ) is defined as the diameter of the circle passing through the inner points of the stator magnetic circuit teeth, forming the working surface of the air gap between the stator and the rotor. Teeth division (t z ), is defined as the distance along the arc of the stator bore between the centers of adjacent teeth (or between the same points of two adjacent grooves), t z =п⋅D ВН / Z, where Z is the number of slots in the stator sheet, n is a mathematical constant expressing the ratio of the circumference to its diameter and equal to 3.1415.

[0024] The number of slots (Z) is defined as the total number of closed slots in the stator magnetic circuit sheet.

[0025] The number of pole pairs (p) is defined as the number of pairs of magnetic poles (north and south) generated by the stator winding.

[0026] The number of slots per pole and phase (q) is defined as the ratio of the number of stator slots to the product of the number of poles and the number of phases: q=Z / (pm), where m is the number of winding phases.

[0027] Fig. 1 shows a general view of a submersible electric motor in longitudinal section, and a stator (1), which is part of the submersible electric motor (longitudinal section).

[0028] Fig. 2 shows a sheet of the stator magnetic circuit (2) with the number of closed slots (3) Z=36.

[0029] Fig. 3 shows an enlarged view of one stator slot with winding wires (4) and slot insulation (5) laid out, illustrating the placement of round wires in the slot and the high degree of filling.

[0030] Fig. 4 shows a graph of the harmonic composition for a valve motor with the proposed geometry (Z=36, 2p=4) in comparison with an analog (Z=18, 2p=4).

[0031] The choice of 36 slots in the stator magnetic circuit sheet is the result of optimization of the stator tooth area. With a fixed stator magnetic circuit sheet outer diameter of 105 mm, the transition from traditional 18 or 24 slots to 36 slots simultaneously reduces the tooth pitch, making it more proportionate to the diameter of the winding wire used, and optimizes the slot shape to achieve maximum packing density of round wires, ensuring an optimal slot-to-pole ratio (Z / 2p) for brushless motors and a denser packing of the winding wire in the slots. For example, for a brushless motor with a 4-pole permanent magnet rotor (total pole number 2p = 4), the number of slots per pole and phase q = Z / (2p⋅m) = 36 / (4⋅3) = 3. The resulting integer value of q means that the winding is integer, which ensures phase symmetry and allows suppression of the most dangerous tooth harmonics (for example, the 5th and 7th).

[0032] The closed groove shape is formed by two parallel straight lines (long sides) and two semicircular arcs (short end sides), facing the outer surface of the sheet and the bore, respectively (Figs. 2, 3). The radius of the semicircle is equal to half the groove width R = b / 2, where b is the groove width. This shape ensures maximum filling of the groove with round winding wires, since the winding wires naturally fit into the grooves, virtually eliminating voids. Furthermore, the absence of sharp corners in the groove cross-section reduces the concentration of mechanical stress in the stamped sheet and the risk of damage to the wire insulation, which in turn leads to highly technological stamping and laying of winding wires.

[0033] The slot geometric parameters, namely the slot width (b) and height (h), are selected to accommodate an integral number of winding wires of a given diameter, taking into account the diameter of the winding wire itself, the thickness of the slot insulation, and the clearances. Typically, the ratio of the slot height (h) to its width (b) ranges from 3.5 to 4.0. The thickness of the slot insulation is 0.25 mm, and the clearances are typically 0.4-0.6 mm greater than the diameter of the winding wire.

[0034] The winding wire is a standard copper wire with a diameter of 3.3-3.5 mm. Because the groove width (b) exceeds the diameter of the winding wire with insulation by 0.4-0.6 mm, the winding wire is laid in one row across the width of the groove and in four rows across the height of the groove. The winding wires fit tightly together, and the short ends, formed by semicircular arcs, ensure virtually no voids.

[0035] In Fig. 1, the electric motor for driving an electric centrifugal pump is submersible and contains a stator 1. The stator is assembled from sheets of electrical steel 2 (Fig. 2, stator magnetic circuit sheet), insulated from each other. The stator magnetic circuit sheets have a stamped configuration with an outer diameter of 105 mm, the internal boring of the stator magnetic circuit sheet (D вн ) is approximately 57 mm. The stator magnetic circuit sheet has 36 teeth and 36 closed identical slots.

[0036] Next, the technical solution of the present utility model will be described in conjunction with embodiment examples. It is obvious that the described embodiment examples represent only a part of the embodiment examples of the present utility model, and not all possible options. A prototype of a stator magnetic circuit sheet with an outer diameter of 105 mm and 36 closed slots was made of electrical steel grade 2215 with a thickness of 0.5 mm (manufactured in accordance with GOST 21427.2-83). The geometric parameters of the closed slots (Fig. 3) were selected for laying a standard copper winding wire of the PPI-U 3.0 brand with insulation made of two layers of polyimide-fluoroplastic film, heat-treated for the purpose of baking (manufactured in accordance with TU 16-705.159-80). The nominal diameter of the copper core (dm) was 3.0 mm, and the diameter of the wire with insulation (diz) was 3.46 mm.The calculated optimal dimensions of the groove for laying the copper winding wire with the given characteristics were: the width of the groove (b) is 4.0 mm (constant), the height of the groove (h) is 15.0 mm, the radius of the semicircle was R=b / 2=2.0 mm, the thickness of the groove insulation was 0.25 mm (taken into account when calculating the free area).

[0037] The radius of the semicircle is equal to half the slot width, ensuring that the round winding wires fit tightly together, while the short ends formed by the arcs of the semicircles ensure virtually no voids. The selected ratio of the slot height to its width (h / b=3.75) ensures that exactly four wires are placed in a row without excess vertical clearance. Four copper winding wires are laid in each of the 36 closed identical slots. The winding wires are laid in one row along the slot width and in four rows along the slot height. The winding wires are arranged so that they completely fill the slot and partially overlap into the areas formed by the arcs of the semicircles, ensuring high packing density. The calculated slot fill factor (kz), defined as the ratio of the total copper cross-sectional area to the cross-sectional area of ​​the slot minus the area of ​​the slot insulation, was 0.75.This value is fully consistent with the data shown in Fig. 3 and significantly exceeds the fill factor for traditional 18- and 24-slot designs, where it is typically 0.59-0.61.

[0038] For the 20 to 200 kW motor range, the above-mentioned copper winding wire (diz = 3.46 mm) and the same number of turns per slot (4 winding wires) are used. With fixed winding parameters (wire diameter, number of turns, connection diagram), increasing the stator (active zone) length proportionally increases the motor's output power, as the volume of copper and steel involved in electromagnetic energy conversion increases. Thus, the stator length was 722 mm for the 20 kW motor and 7580 mm for the 200 kW motor. This confirms production standardization.

[0039] For a valve motor with a 4-pole rotor on permanent magnets (2p=4), calculation using the finite element method showed a decrease in the harmonic content from 9% (at Z=18) to 6% (at Z=36), which increases the smoothness of the run and the service life of the bearings (Fig. 4).

[0040] When voltage is applied to the stator winding, a rotating magnetic field is generated that interacts with the rotor. Thanks to the optimized geometry of the tooth and groove zone (Z=36, the grooves, each formed by two parallel straight lines (long sides) and two semicircular arcs (short end sides), facing the outer surface of the sheet and the bore, respectively, this results in a more uniform field distribution in the gap, reduced steel losses and tooth pulsation, and a high slot fill factor, which allows for either increased power with the same dimensions or reduced heating.

Claims

1. A sheet of the magnetic circuit of the stator of a submersible electric motor for driving an electric centrifugal pump, containing teeth, grooves for laying the winding wire, characterized in that the sheet is made for an electric motor with an outer diameter of the stator of 105 mm and contains 36 closed identical grooves formed by two parallel straight lines, which are the long sides, and two arcs of semicircles, which are the short end sides, facing respectively the outer surface of the sheet and the bore, wherein the radius of the semicircle (R) is equal to half the width of the groove, and the ratio of the height (h) of the groove to its width (b) is from 3.5 to 4.

0.

2. A sheet according to paragraph 1, characterized in that the width of the groove exceeds the outer diameter of the winding wire with insulation by the value of the technological gap.

3. A sheet according to paragraph 2, characterized in that the size of the technological gap is 0.4-0.6 mm.

4. A sheet according to paragraph 1, characterized in that the winding wires are laid in an orderly manner in the grooves.

5. The sheet according to item 4, characterized in that the groove contains one row of winding wire in width and four rows of winding wire in height.

6. A sheet according to paragraph 1, characterized in that the diameter of the winding wire is selected in proportion to the width of the groove.

7. A sheet according to paragraph 1, characterized in that the distance between the teeth (teeth division) is proportional to the diameter of the winding wire.

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