Method for manufacturing immersion motor

Abstract

A method for manufacturing an immersion motor according to an embodiment is for manufacturing an immersion motor that is driven while being immersed in anhydrous ammonia, wherein a plurality of conductive wires constituting a stator coil are attached to a stator core, a first coating film of a polyethylene-based thermal fusion material is formed by a powder coating method on the entire stator core to which the plurality of conductive wires are attached, a rotor core is attached to a rotor, a second coating film of the polyethylene-based thermal fusion material is formed by the powder coating method on the entire rotor to which the rotor core is attached, and the rotor on which the second coating film is formed is attached to the stator core on which the first coating film is formed.

Description

Immersion motor manufacturing method

[0001] SUMMARY OF THE INVENTION An embodiment of the present invention relates to a method for manufacturing an immersion motor.

[0002] 2. Description of the Related Art Conventionally, a submerged pump having a canned motor is known as a submerged pump that is immersed in anhydrous ammonia (dry ammonia) stored in a low-temperature storage tank and used to pump out the anhydrous ammonia.

[0003] Japanese Patent Application Publication No. 6-081797

[0004] In a canned motor, a wide gap must be provided between the stator and rotor.

[0005] This reduces the efficiency of the motor and the pumping capacity of the submerged pump. Furthermore, a casing is required to house the pump and motor in a sealed unit, which increases the manufacturing costs of the canned motor and, ultimately, the submerged pump.

[0006] Furthermore, if a submerged pump is directly immersed in anhydrous ammonia, and an ester amide resin having an amide bond or an ester resin having an ester bond is used as a conventional coating material and impregnating resin, there is a risk that the coating material and the impregnating resin will be decomposed by the anhydrous ammonia, resulting in deterioration of the coating material and the impregnating resin.

[0007] The present invention has been made in view of the above, and an object of the present invention is to provide a method for manufacturing an immersion motor that can be operated with its stator and rotor directly immersed in anhydrous ammonia.

[0008] In one embodiment, a method for manufacturing an immersion motor is a method for manufacturing an immersion motor that is driven while immersed in anhydrous ammonia, and includes assembling a plurality of conducting wires that constitute a stator coil to a stator core, forming a first coating of a polyethylene-based heat-sealing material on the entire stator core to which the plurality of conducting wires are assembled by powder coating, assembling the rotor core to a rotor, forming a second coating of a polyethylene-based heat-sealing material on the entire rotor to which the rotor core is assembled by powder coating, and assembling the rotor with the second coating formed to the stator core with the first coating formed.

[0009] According to this embodiment, a method for manufacturing an immersion motor is provided that can be operated with the stator and rotor directly immersed in anhydrous ammonia.

[0010] FIG. 1 is an explanatory diagram of the installation state of an anhydrous ammonia immersion pump according to an embodiment. FIG. 2 is a cross-sectional view of an anhydrous ammonia immersion pump according to an embodiment. FIG. 3 is a diagram showing an example of the steps of a method for manufacturing an anhydrous ammonia immersion motor according to an embodiment. FIG. 4 is a diagram showing an example of the steps of a method for manufacturing an anhydrous ammonia immersion motor according to an embodiment. FIG. 5 is a cross-sectional view showing the fusion of a coated conductor wire when coating a stator core according to an embodiment. FIG. 6 is a cross-sectional view showing the fusion of a coated conductor wire when coating a stator core according to a modified embodiment. FIG. 7 is a schematic explanatory diagram of the configuration of an anhydrous ammonia immersion-energization test device used to test an anhydrous ammonia immersion motor according to an example.

[0011] Preferred embodiments will be described in detail below with reference to the drawings.

[0012] (Configuration Example of Anhydrous Ammonia Submerged Pump) Figure 1 is an explanatory diagram of the installation state of an anhydrous ammonia submerged pump 10 according to an embodiment. The anhydrous ammonia submerged pump 10 is installed in a prestressed concrete (PC) tank 2 that stores liquefied ammonia 1, and is a device that pumps the liquefied ammonia 1 from the PC tank 2 to the outside.

[0013] Here, the PC tank 2 comprises an outer tank roof 2A, an outer tank liner 2B, a cold insulation material 2C, a cold and heat resistance mitigation material 2D, an inner tank 2E, a PC liquid barrier 2F, and a base mat 2G.

[0014] The outer tank roof 2A and the outer tank liner 2B constitute the outer tank, which, together with the inner tank 2E, forms a double-shell structure. The base mat 2G is supported by a plurality of steel pipe piles (not shown) driven into the supporting layer underground.

[0015] The liquefied ammonia 1 in the PC tank 2 is, more specifically, anhydrous liquefied ammonia (anhydrous ammonia) or the like, and has a boiling point of −33.34° C. Because hydrogen can be produced by catalytic combustion of the liquefied ammonia 1, it is also being studied as an alternative method for storing hydrogen.

[0016] FIG. 2 is a cross-sectional view of an anhydrous ammonia submerged pump 10 according to an embodiment.

[0017] As shown in FIG. 2 , the anhydrous ammonia submerged pump 10 of this embodiment includes a multi-stage centrifugal pump 11 and an anhydrous ammonia submerged motor 12 .

[0018] The multi-stage centrifugal pump 11 includes a pump shaft 21, a centrifugal pump 22, and a pump case 23, and discharges anhydrous ammonia in the PC tank to the outside via a column.

[0019] The centrifugal pump 22 includes multiple impellers integrally arranged with the pump shaft 21 and functions as a pump body. In the example of Fig. 2, the multi-stage centrifugal pump 11 is provided with five centrifugal pumps 22. However, the number of centrifugal pumps 22 can be determined appropriately based on the required performance.

[0020] The pump case 23 houses the pump shaft 21 and the centrifugal pump 22 .

[0021] The anhydrous ammonia immersed motor 12 includes a motor shaft 31 , a rotor 32 , a stator 33 , and a motor case 34 , and functions as an immersed motor that drives the multi-stage centrifugal pump 11 .

[0022] The motor shaft 31 is made of, for example, stainless steel and is rotatably supported by bearings 35 provided in a motor case 34. The motor shaft 31 is coaxially connected to the pump shaft 21 of the multi-stage centrifugal pump 11 and functions as an output shaft that transmits the output of the anhydrous ammonia immersed motor 12 to the pump shaft 21.

[0023] The rotor 32 is a magnetic body formed in a cylindrical shape concentric with the motor shaft 31 and is fixed to the motor shaft 31. The rotor 32 includes a rotor core 36 formed by, for example, laminating silicon steel plates in the axial direction.

[0024] The stator 33 is disposed around the rotor 32 with a gap therebetween, and faces the circumferential surface of the rotor 32. The stator 33 includes a stator coil 37 and a stator core .

[0025] The stator coil 37 includes a coated conductor. The conductor portion of the coated conductor is, for example, a copper wire. The coating material for the conductor can be, for example, PVF (Poly Vinyl Fluoride) resin or PEEK (Poly Ether Ether Ketone) resin. In this case, it is more preferable to use PVF resin with a melting point of 120° C. or less.

[0026] Resin is impregnated between the stator coils 37 to fill the gaps between the coated conductors. Examples of the impregnating resin include polyethylene (PE) resin, polypropylene (PP) resin, and polystyrene (PS) resin. In this case, it is more preferable to use a polyethylene-based heat-sealing material such as polyethylene resin with a melting point of 120°C or less.

[0027] The stator core 38 and the rotor core 36 are also called the stator core and the rotor core, respectively, and are coated with polyethylene (PE) resin, polypropylene (PP) resin, or polystyrene (PS) resin. In this case, it is more preferable to use a polyethylene-based heat-sealing material such as polyethylene resin having a melting point of 120°C or less.

[0028] The stator 33 having the stator coil 37 and the stator core 38 is also called an iron core slot, and the electric wires in the stator 33 are fixed in the stator 33 by heating and melting a low-melting-point thermoplastic resin such as polyethylene resin to bond them.

[0029] With the above configuration, when current is applied to the stator coil 37 of the anhydrous ammonia immersion motor 12, a rotating magnetic field is generated in the stator 33. The generated rotating magnetic field also generates an attractive force in the rotor 32, causing the rotor 32 to rotate. This in turn causes the motor shaft 31, to which the rotor 32 is fixed, to rotate in a predetermined direction.

[0030] At this time, pump shaft 21 is coaxially connected to motor shaft 31. Therefore, centrifugal pump 22, which is disposed integrally with pump shaft 21 and includes a plurality of impellers, also rotates in a predetermined direction, and the surrounding anhydrous ammonia is transported in the direction indicated by the arrow in Figure 2, and ultimately the anhydrous ammonia in the PC tank can be pumped to the outside.

[0031] It is known that when resin or the like is immersed in liquefied ammonia, the immersed material may undergo ammonolysis (hereinafter referred to as ammonolysis) in the same manner as hydrolysis.

[0032] For example, methyl p-nitrobenzoate is dissolved in liquefied ammonia (NH ３ When the film is immersed in ammonia, ammonia acts on the ester bond of methyl p-nitrobenzoate, causing it to decompose into p-nitrobenzamide and methanol.

[0033] As described above, the insulating material used in the anhydrous ammonia immersion motor 12 is a polyethylene-based heat-sealing material, the copper wire coating material is a PVF resin or a resin composed of ketone or ether bonds such as PEEK resin, and the metal material is coated with the same resin as the insulating material or the wire coating material. All of these resins are corrosion-resistant to anhydrous ammonia.

[0034] As a result, the insulating material and wire coating material of the anhydrous ammonia immersed motor 12 of this embodiment can ensure a lifespan of more than one year in an environment of −33° C. even when directly immersed in anhydrous ammonia.

[0035] (Method of Manufacturing an Anhydrous Ammonia Submerged Motor) Next, a method of manufacturing the anhydrous ammonia submerged motor 12 according to the embodiment will be described with reference to Figures 3 to 5. Of Figures 3 to 5, Figures 3 and 4 are diagrams showing an example of the steps of the method of manufacturing the anhydrous ammonia submerged motor 12 according to the embodiment.

[0036] 3 and 4 are cross-sectional views of the anhydrous ammonia immersed motor 12 during manufacture, and the lower views are longitudinal sectional views of the anhydrous ammonia immersed motor 12 during manufacture. More specifically, the upper views of Figures 3 and 4 are cross-sectional views taken along line B-B of the corresponding views in the lower views, and the lower views of Figures 3 and 4 are cross-sectional views taken along line A-A of the corresponding views in the upper views.

[0037] 3 and 4 also show some components that are omitted from FIG. 2 and are necessary for explaining the manufacturing method of the anhydrous ammonia immersion motor 12.

[0038] As shown in FIGS. 3A and 3B, the stator core 38 has a cylindrical shape, and a plurality of grooves (slots) 38g are formed on the inner wall surface of the stator core 38.

[0039] 3(Ab) and 3(Bb), the entire inner wall surface of the stator core 38 is covered with insulating paper 39p so as to fit along the inner wall surface of the stator core 38. The insulating paper 39p protects the stator core 38 and is also used to protect and hold the stator coil 37 that will be assembled into the stator core 38 in a subsequent process.

[0040] 3(A) and 3(Bc), a plurality of coated conductor wires 37e are housed in a plurality of grooves 38g of the stator core 38. The coated conductor wires 37e are components that constitute the stator coil 37, and a plurality of coated conductor wires 37e are housed in each of the grooves 38g of the stator core 38. As described above, the conductor portion of the coated conductor wires 37e is a copper wire or the like, and is covered with a covering material such as PVF resin or PEEK resin.

[0041] As shown in Figures 4(Aa) and (Ba), multiple coated conductors 37e housed in each groove 38g are connected to each other between different grooves 38g, and multiple coated conductors 37e housed in the same groove 38g are tied together with thread 37s.

[0042] The coated conductor wires 37e are connected between different grooves 38g at the upper and lower ends of the stator core 38, but in Figure 4(Aa) and subsequent figures, wiring 37w that connects the coated conductor wires 37e between different grooves 38g is illustrated to make it easier to understand.

[0043] 4(Ab) and 4(Bb), an impregnation resin 39v such as polyethylene resin, polypropylene resin, or polystyrene resin is applied to the inner wall surface of the stator core 38. As a result, the impregnation resin 39v also permeates into the grooves 38g of the stator core 38, impregnating the grooves 38g so as to fill gaps between the multiple coated conductor wires 37e housed in the grooves 38g.

[0044] 4(A) and 4(Bc), the entire stator core 38 including the plurality of coated conductor wires 37e is coated with a coating film 33c of polyethylene resin, polypropylene resin, polystyrene resin, etc. At this time, powder coating is preferably used as a coating method for the stator core 38, and fluidized bed coating is more preferably used as one of the powder coating methods.

[0045] In the powder coating method, a powder coating material is applied to a metal member to be coated, such as the stator core 38, and then heated, dried, and fixed to form the coating film 33c.

[0046] In the fluidized bed coating method, the stator core 38 or other object to be coated, which has been heated in advance, is placed in a container called a fluidized bed tank, which contains powder paint, and compressed air is then introduced into the container. This causes the powder paint to flow through the container and adhere to the object to be coated, such as the stator core 38. The adhered powder paint melts and solidifies due to the heat of the object to be coated, forming a coating film 33c that covers the entire stator core 38.

[0047] As described above, by using powder coating, or more preferably fluidized bed coating, the entire stator core 38 including the plurality of coated conductor wires 37 e is coated with the coating film 33 c. At this time, the welded portions of each member of the stator core 38 are also coated, so that the entire member is sealed with the coating film 33 c, and good corrosion resistance to anhydrous ammonia can be obtained.

[0048] At this time, it is preferable that the coating material of each coated conductor 37e and the impregnated resin 39v impregnated in these coated conductors 37e are fused together when coating the stator core 38, etc. using powder coating or the like.

[0049] As described above, by using, for example, PVF resin and polyethylene resin, which have melting points of 120° C. or less, for the coating material of the coated conductor 37 e and the impregnating resin 39 v, respectively, these can be fused together during coating. Fig. 5 shows how the coating material of the coated conductor 37 e and the impregnating resin 39 v are fused together by coating using fluidized bed coating.

[0050] FIG. 5 is a cross-sectional view showing the fusion of the coated conductor wires 37e when coating the stator core 38 according to the embodiment.

[0051] 5A, before coating the stator core 38 by fluidized bed coating, the inner wall surface of the stator core 38 is covered with insulating paper 39p. A plurality of coated conductor wires 37e are housed in each of the grooves 38g of the stator core 38 covered with insulating paper 39p. Furthermore, the gaps between the coated conductor wires 37e are filled with impregnating resin 39v.

[0052] Here, the coated conductor 37e has a configuration in which the periphery of a conductor 371, such as a copper wire, is covered in this order with an insulating layer 372 and a fusion layer 373. As described above, the insulating layer 372 and the fusion layer 373, which are the coating materials for the conductor 371, are made of, for example, PVF resin or PEEK resin. In this case, it is preferable to use PVF resin with a melting point of 120° C. or lower for the fusion layer 373.

[0053] 5(b), the stator core 38 in the above-described state with the plurality of coated conductor wires 37e attached thereto is preheated as a whole, and then placed in a fluidized bed tank, where the entire core is coated with the coating film 33c by fluidized bed dip coating. The preheating temperature of the stator core 38 is preferably equal to or close to the temperature of the powder to be fluidized bed dip.

[0054] The fusion layer 373 of the exterior of the coated conductor wires 37e and the impregnated resin 39v between the coated conductor wires 37e melt due to heat generated when the stator core 38 is preheated or when the stator core 38 is coated, fusing the coated conductor wires 37e housed in the same groove 38g together. This unifies the multiple coated conductor wires 37e in the groove 38g, improving the insulation of the coated conductor wires 37e and holding the coated conductor wires 37e more firmly in the groove 38g of the stator core 38.

[0055] The coated conductor wires 37e may be coated with powder resin used in fluidized bed coating before being placed in the grooves 38g of the stator core 38. This allows the coated conductor wires 37e to be more firmly integrated with each other, further improving the corrosion resistance of the coated conductor wires 37e to anhydrous ammonia.

[0056] In this manner, the stator 33 including the stator core 38 and the stator coil 37 shown in FIG. 2 is manufactured.

[0057] The coating method using fluidized bed coating for the stator 33 can also be applied to the rotor 32. That is, the entire rotor 32, to which the rotor core 36 and other components are assembled, is preheated, placed in a fluidized bed tank, and then coated with a coating film by fluidized bed coating.

[0058] As a result, the welded portions of each member of the rotor 32 are also coated, so that the entire member is sealed with the coating, and good corrosion resistance to anhydrous ammonia can be obtained.

[0059] Thereafter, the rotor 32 fixed to the motor shaft 31 is inserted into the stator 33, and the whole is housed in the motor case .

[0060] As a result of the above, the anhydrous ammonia immersion motor 12 including the motor shaft 31, the rotor 32, the stator 33, and the motor case 34 is manufactured.

[0061] (Overview) An anhydrous ammonia submersible pump, which is submerged in a tank storing anhydrous ammonia and pumps out the anhydrous ammonia, uses a canned motor to suppress ammonolysis caused by the anhydrous ammonia. A canned motor is an integrated pump and motor housed in a sealed can.

[0062] However, in a canned motor, a large gap between the stator and rotor is required to accommodate the casing, which reduces the efficiency of the canned motor and increases the overall capacity. The need for a casing to house the pump and motor together in a sealed state also increases manufacturing costs.

[0063] On the other hand, if an uncased motor is used in an anhydrous ammonia immersion pump and is directly immersed in anhydrous ammonia, there is a risk that ammonolysis by anhydrous ammonia will occur in the components of the motor.

[0064] For example, esterimide resin, polyester resin, or the like is typically used as the coating material for the coated conductors that make up the stator coil 37. Furthermore, epoxy-based resins or the like are used as the impregnating resins used to impregnate the coated conductors. These coating materials and impregnating resins are not sufficiently corrosion-resistant to anhydrous ammonia and deteriorate when immersed in anhydrous ammonia. Furthermore, because the above-mentioned coating materials are easily scratched, if the coating cracks, the internal conductors become exposed. When a voltage is applied, an electrochemical reaction occurs, causing a large current to flow.

[0065] According to the manufacturing method of the anhydrous ammonia immersed motor 12 of the embodiment, a coating film 33c of a polyethylene-based heat-sealing material is formed by powder coating on the entire stator core 38 to which the multiple coated conductor wires 37e are assembled. This allows the coating film 33c to be formed on the welded portions of each member of the stator 33 as well, thereby improving the corrosion resistance of the stator 33 to anhydrous ammonia.

[0066] According to the manufacturing method of the anhydrous ammonia immersed motor 12 of the embodiment, a coating film of a polyethylene-based heat-sealing material is formed by powder coating on the entire rotor 32 to which the rotor core 36 is assembled. This allows the coating to be formed on the welded portions of each member of the rotor 32 as well, improving the corrosion resistance of the rotor 32 to anhydrous ammonia.

[0067] According to the manufacturing method of the anhydrous ammonia immersed motor 12 of the embodiment, the rotor 32 on which the coating film is formed is assembled to the stator core 38 on which the coating film 33c is formed, thereby obtaining the anhydrous ammonia immersed motor 12 that can be operated while directly immersed in anhydrous ammonia.

[0068] According to the manufacturing method of the anhydrous ammonia immersed motor 12 of the embodiment, the plurality of conductors 371 are coated with formal resin, polyether ether ketone resin, or polyethylene resin before being assembled to the stator core 38. This prevents deterioration of the adhesive layer 373, which is the coating material of the coated conductors 37e, and improves the corrosion resistance of the coated conductors 37e against anhydrous ammonia, thereby preventing large currents from flowing through them.

[0069] According to the manufacturing method of the anhydrous ammonia immersion motor 12 of the embodiment, when forming the coating film 33c on the stator core 38, the entire stator core 38 is preheated, the entire preheated stator core 38 is placed in a fluidized bed tank, and the powder paint is fluidized in the fluidized bed tank containing the stator core 38. In this way, by using the fluidized bed dip coating method, the corrosion resistance of the stator 33 to anhydrous ammonia can be further improved.

[0070] According to the manufacturing method of the anhydrous ammonia immersed motor 12 of the embodiment, when the coating film 33c is formed on the stator core 38, the coating material of the plurality of coated conductor wires 37e is melted to fuse the plurality of coated conductor wires 37e together, thereby further improving the corrosion resistance of the coated conductor wires 37e against anhydrous ammonia.

[0071] According to the manufacturing method of the anhydrous ammonia immersed motor 12 of the embodiment, when the plurality of conductors 371 are assembled to the stator core 38, they are impregnated with the impregnation resin 39v, which is a thermoplastic polyethylene resin, to fix the plurality of conductors 371. This prevents deterioration of the impregnation resin 39v and further improves the corrosion resistance of the coated conductors 37e against anhydrous ammonia.

[0072] (Modification) Next, a method for manufacturing an anhydrous ammonia immersion motor according to a modification of the embodiment will be described with reference to Fig. 6. In the method for manufacturing an anhydrous ammonia immersion motor according to the modification, the method for assembling the coated conductor wire 37e differs from that of the above-described embodiment.

[0073] 6 is a cross-sectional view showing the fusion of the coated conductor wires 37e when coating the stator core 38 according to the modified embodiment. In the following drawings, the same reference numerals are used to designate the same components as those in the above-described embodiment, and the description thereof may be omitted.

[0074] 6(a), before coating the stator core 38 by fluidized bed dip coating, a plurality of coated conductor wires 37e are housed in each of the grooves 38g of the stator core 38 covered with insulating paper 39p. However, in the manufacturing method of the modified example, the above-mentioned impregnation resin 39v or the like is not impregnated between the coated conductor wires 37e.

[0075] In this case, the coated conductor wires 37e may also be previously coated with powder resin used in fluidized bed coating.

[0076] 6(b), when fluidized bed coating is performed on the stator core 38, the fusion layer 373 on the exterior of the coated conductor wires 37e melts during preheating or coating of the stator core 38, and the coated conductor wires 37e housed in the same groove 38g fuse together. This makes it possible to sufficiently improve the insulation of the coated conductor wires 37e and firmly hold the coated conductor wires 37e in the grooves 38g of the stator core 38 without using the above-mentioned impregnation resin 39v or the like.

[0077] As described above, ammonolysis may occur even in an environment where water is not present, and therefore, when manufacturing a liquefied ammonia immersion motor or a liquefied ammonia immersion pump, an ammonia immersion test (qualitative test) must be performed to evaluate the ammonia immersion.

[0078] Therefore, an anhydrous ammonia immersion test was carried out on insulating materials, conductors, insulating resins, coated conductor wires and metal materials.

[0079] (1) Insulating materials and conductors The following materials are subject to the anhydrous ammonia immersion test.

[0080] Furukawa Electric cable: Insulation: cross-linked polyethylene, sheath: vinyl, conductor: hard aluminum wire, Junkosha cable: Insulation: PTFE, conductor: tin-plated copper wire, V354 resin-impregnated mica, electrical steel sheet, DuPont Nomex (registered trademark), welded parts, enamelled wire, Sumitomo Seika Chemicals Fluothane (registered trademark) W380A, Sumitomo Seika Chemicals Fluothane (registered trademark) 19132 white.

[0081] In the anhydrous ammonia immersion test, the samples were immersed in anhydrous ammonia in a 100 cc SUS container for one week. As a result of the test, no change was observed in the appearance of the immersed samples.

[0082] (2) Insulating resins The insulating resins covered were V354 resin (epoxy resin), random winding varnish (B21 varnish), enameled wire coating (polyester amide, etc.), and polyethylene powder (assuming powder coating).

[0083] In the anhydrous ammonia immersion test, the sample was immersed in anhydrous ammonia in a 100 cc SUS container for one week.

[0084] The test results showed that the V354 resin (epoxy resin) liquefied. The random winding varnish (B21 varnish) decomposed slightly. The enamelled wire coating (polyester amide, etc.) decomposed. The polyethylene powder remained unchanged.

[0085] These results indicate that there is a concern about ammonolysis of insulating resins, and that it is necessary to consider changing the material or using powder coating for protection.

[0086] (3) Coated Conductive Wire The coated conductor wires used were those whose coating material was polyurethane resin, polyester resin, polyimide resin, PVF (Poly Vinyl Fluoride) resin, or PEEK (Poly Ether Ether Ketone) resin.

[0087] In the anhydrous ammonia immersion test, the sample was immersed in anhydrous ammonia in a 100 cc SUS container for one week.

[0088] As a result of the immersion test, it was found that coatings with hydrolyzable structures such as polyurethane resin, polyester resin, and polyimide resin were decomposed during immersion in anhydrous ammonia.

[0089] In contrast, it was found that a coating of a resin composed of ketone or ether bonds, such as PVF resin or PEEK resin, can withstand immersion in anhydrous ammonia.

[0090] (4) Metallic materials For metallic materials, taking into consideration the case where electricity is passed through them as conductors, an anhydrous ammonia immersion-current test was conducted by passing electricity through them during the anhydrous ammonia immersion test to verify the elution and electrolysis of ions in the metal and polar components in the polymer due to the passage of electricity.

[0091] FIG. 7 is a schematic diagram illustrating the configuration of an anhydrous ammonia immersion-energization test device used to test the anhydrous ammonia immersion motor according to the embodiment.

[0092] The anhydrous ammonia immersion-current test device 50 comprises a DC power supply 51 , a copper electrode 52 , an electrode connector 53 , test electrodes 54 A and 54 B, a gas introduction pipe 55 , a pressure gauge 56 , and a test container 57 .

[0093] A DC power supply 51 applies a DC voltage between the test electrode 54A and the test electrode 54B via a pair of copper electrodes 52 and a pair of electrode connectors 53 while increasing the voltage at a predetermined rate.

[0094] A pair of copper electrodes 52 and a pair of electrode connectors 53 supply DC power from a DC power supply 51 to test electrodes 54A and 54B.

[0095] The test electrodes 54A and 54B are made of the same metal material, and are configured as flat plate electrodes whose opposing surfaces 54A1 and 54B1 are substantially square.

[0096] The gas inlet pipe 55 supplies anhydrous ammonia 60 into the test vessel 57 and transmits the pressure inside the test vessel 57 to the pressure gauge 56 .

[0097] The pressure gauge 56 measures the pressure inside the test vessel 57 .

[0098] The voltage and current of the DC power supplied by the DC power supply 51 and the pressure measured by the pressure gauge 56 are recorded in chronological order by a logging device (not shown).

[0099] Next, the anhydrous ammonia immersion-current test will be specifically described.

[0100] The metal materials used to form the test electrodes 54A and 54B were iron (Fe), copper (Cu), and aluminum (Al).

[0101] The current was limited to a maximum of 1 mA, the voltage was approximately the rated voltage of the anhydrous ammonia immersed motor (up to 1 kV), and the test temperature was room temperature. The pressure inside the sealed test vessel 57 was measured in parallel with the test by a pressure gauge 56.

[0102] In this case, the test electrodes 54A and 54B are arranged in the test container 57 so that the opposing surfaces 54A1 and 54B1 are opposed to each other with a predetermined distance between them.

[0103] Prior to the anhydrous ammonia immersion test, electrical conduction was confirmed.

[0104] Specifically, before anhydrous ammonia was introduced into the test vessel 57, the DC power supply 51 started to apply a voltage to the empty vessel, and the voltage was increased at a rate of approximately 10 V / sec until a voltage of 1 kV was applied (requiring approximately 100 sec).

[0105] During the voltage application period, the current was 0 mA, and the pressure inside the sealed test vessel 57 was constant at about 0.1 MPa (≈ atmospheric pressure [1 atmosphere]).

[0106] Next, anhydrous ammonia was poured into the test container 57 until the opposing surfaces 54A1 of the iron test electrode 54A and 54B1 of the iron test electrode 54B were immersed, the container was sealed, and a voltage was applied in the same manner as when checking the electrical conductivity.

[0107] As a result, the voltage was maintained at 0 V and the current at 0 mA for approximately 2.5 seconds after the voltage was applied, and then when the voltage reached 50 V, the current reached the limit current of 1 mA, so the current was stopped.

[0108] At this time, the pressure inside the sealed test vessel 57 was constant at about 1 MPa (≈10 atmospheres).

[0109] These results indicate that anhydrous ammonia behaves similarly to pure water and may be conductive even when electrolytes such as metals are not eluted.

[0110] The above results were obtained for the test electrodes 54A and 54B made of iron, but similar results were also obtained for the test electrodes 54A and 54B made of copper and aluminum.

[0111] (5) Conclusion Based on the experimental results of (1) to (4) above, it was found that it is best to use a polyethylene-based heat-sealing material (for powder coating) as the insulating material for an ammonia immersion motor or ammonia immersion pump, use a resin composed of ketone or ether bonds such as PVF resin or PEEK resin as the copper wire coating material, and mold the metal material with the same resin as the insulating material or conductor coating material.

[0112] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims.

[0113] 1 Liquefied ammonia 2 PC tank 10 Anhydrous ammonia immersion pump 11 Multistage centrifugal pump 12 Anhydrous ammonia immersion motor 21 Pump shaft 22 Centrifugal pump 23 Pump case 31 Motor shaft 32 Rotor 33 Stator 33c Coating 34 Motor case 35 Bearing 36 Rotor core 37 Stator coil 37e Coated conductor 37s Thread 37w Wiring 38 Stator core 38g Groove 39p Insulating paper 39v Impregnated resin 50 Anhydrous ammonia immersion - current test device 51 DC power supply 52 Copper electrode 53 Electrode connector 54A Test electrode 54B Test electrode 54A1, 54B1 Opposing surface 55 Gas introduction pipe 56 Pressure gauge 57 Test container 371 Conductor 372 Insulating layer 373 Fusion layer

Claims

1. A method for manufacturing an immersion motor that is driven while immersed in anhydrous ammonia, comprising the steps of: assembling a plurality of conducting wires that constitute a stator coil into a stator core; forming a first coating of a polyethylene-based heat-sealing material by powder coating on the entire stator core to which the plurality of conducting wires are assembled; assembling the rotor core into a rotor; forming a second coating of a polyethylene-based heat-sealing material by powder coating on the entire rotor to which the rotor core is assembled; and assembling the rotor with the second coating formed on it to the stator core with the first coating formed on it.

2. The method for manufacturing an immersion motor according to claim 1, wherein the plurality of conducting wires are coated with formal resin, polyether ether ketone resin, or polyethylene resin before being assembled to the stator core.

3. A method for manufacturing an immersion motor as described in claim 1, wherein when forming the first coating film on the stator core, the entire stator core is preheated, the entire preheated stator core is placed in a deep fluidizing tank, and powder paint is allowed to flow within the deep fluidizing tank in which the stator core is placed.

4. A method for manufacturing an immersion motor as described in claim 3, wherein before assembling the plurality of conductors to the stator core, the plurality of conductors are coated with formal resin, polyether ether ketone resin, or polyethylene resin to form a plurality of coated conductors, and when forming the first coating film on the stator core, the coating material of the plurality of coated conductors is melted to fuse the plurality of coated conductors together.

5. The method for manufacturing an immersion motor according to claim 1, wherein when the plurality of conductors are assembled to the stator core, thermoplastic polyethylene resin is impregnated between the plurality of conductors to fix the plurality of conductors.

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