ITMI961082A1 - APPARATUS AND METHOD FOR COATING SURFACES WITH ROTOR SHEETS AND MATERIALS FOR THE SAME - Google Patents

Description

DESCRIPTION of the industrial invention

This invention relates generally to electric motors and, more particularly, to electrically and mechanically separating, or insulating, a rotor core from rotor rods and head rings of an electric motor.

Known alternating current induction motor rotors typically comprise a rotor core formed by a plurality of laminations. In a known configuration, each lamination is sheared from a sheet of steel and contains a rotor shaft opening and a plurality of rotor bar openings spaced apart and disposed radially adjacent the outer periphery of the laminations. The laminations are arranged in a stack up to a height of, for example, from 25 to 150 mm (from I to 6 inches). The laminations may be slightly skewed and welded or crimped together to form the rotor core.

This rotor core typically contains a longitudinal opening of the rotor shaft and a plurality of longitudinal slots for rotor bars. Rotor bar slots are sometimes called secondary conductor slots. Following an aluminum die casting operation, rotor rods extend through the rotor rod slots and head rings together short the rods at opposite ends of the rotor core. Such a rotor is sometimes referred to in the art as a "squirrel cage" type rotor.

Compared to the slots for rotor bars, the surfaces of the laminations at the outer periphery of each slot preferably have electrical resistance to reduce losses in the motor due to currents flowing through the laminations of the rotor, in particular, in operation, currents are induced in the rotor rods and if the rotor rods and laminations are in electrical contact, at least some current flow will be established in the laminations. By providing a high resistance to the outer periphery of each bar, this current passage in the laminations can be low and the resulting performance of the motor is affected. In addition and to further reduce such losses, the rotor core is preferably isolated, or mechanically separated from the rotor rods. This construction improves the performance of the engine and the starting characteristics.

It is known to perform "bluing" operations in the furnace to form an oxide layer on the engine core laminations. The oxide layer provides a high electrical resistance and mechanical separation between the rotor bars and the surfaces of the rotor laminations at the periphery of the rotor bars themselves. In particular and with respect to a known "bluing" operation before casting the rotor bars and the head rings, the rotor core is placed in an annealing furnace. The rotor core is annealed so that a resistive oxide coating on the core surfaces The annealing process is called "bluing" since the rotor core steel sheets generally have a bluish color as a result of proper annealing operation.

Although blueing provides satisfactory results, an annealing furnace generally consumes large amounts of energy in operation and the rotor core typically must be placed within such a furnace operating for a long period in order to form an acceptable oxide. Although the core may be annealed for an extended period of time, the oxide coating formed on the laminations may not have consistent thickness or uniformity. A known inorganic coating to be used as an insulator in transformers and in large rotating equipment, such as turbines, is an aqueous dispersion of kaolin-type clay, iron oxide and a phosphate binder. To apply the coating, the metal surface of the transformer to be coated is first "preheated". This preheating prevents the separation of the clay, the iron oxide charge and the phosphate binder during drying. After the preheating operation, the coating material is applied to the metal surface and heated to a temperature above 180 ° C so that the phosphate decomposes and forms a polyphosphate showcase reinforced by the charge.

Although this known organic coating is effective, in order to establish optimum coating thickness and uniformity, the inorganic coating must be substantially diluted. Such dilution destabilizes the dispersion and requires the dispersion to be stirred constantly to maintain uniformity. In addition, the dispersion has pH instability. A consistent high pH is desirable, however, to provide solubilization that better ensures the application of a uniform coating thickness and excellent adhesion of the coating.

Additionally, the dispersion has a red color that could be mistaken for rust. Obviously, if rust or appearance of rust is observed, the metal surface must be clean, which adds to the manufacturing costs and increases the manufacturing time.

It would be desirable, therefore, to provide a process for forming a high strength film on selected surfaces of rotor laminations which eliminates a need for annealing and establishes a substantially uniform film on selected rotor surfaces. It would also be desirable to provide a coating material that has good adhesion to steel, better dispersion stability at the concentration required for coating uniformity, a consistent high pH for solubilization and stability, transparent coloring and preventing separation of the binder from the charge for drying. These and other advantages are provided by the rotor core coating materials and methods disclosed herein. More particularly, and in one aspect, the coating material is an aqueous based inorganic solution or mixture of diammonium phosphate (DAP), monoammonium phosphate (MAP) and an ammonia stabilized colloidal silica. To form a highly resistive film on a rotor core, the core is cleaned and preheated using, for example, induction heating. The coating material is then applied to selected rotor core surfaces. The core is then dried and the coating material hardened. The cured coating material forms a highly resistive film on the selected core surfaces.

When formed on the lamination surfaces at the outer periphery of the rotor rod slots, the film provides a high strength between the rotor rods and the laminations and also allows for good mechanical separation between the rotor rods and the rotor core. In addition, the film has good adhesion to steel and the coating material has improved blend stability as the blend does not require constant stirring to maintain uniformity. Also, the coating material has improved wettability characteristics and forms a substantially uniform film. Furthermore, the coating material is colorless and the binder does not separate from the charge by drying. The above-described coating process also eliminates the time-consuming and energy-consuming "bluing" operation in the oven.

Figure I is a top plan view of a rotor lamination. Figure 2 is a perspective view of a rotor core.

Figure 3 is a flow chart illustrating a process step sequence for coating a rotor core.

Figure 4 is a schematic illustration of injection tools that can be used in injecting coating material into slots for rotor bars of a rotor core.

Figure 5 is a top view of a rotor core indicating sealing areas touched by sealing rings of the injection tool illustrated in Figure 4.

Figure 6 is a schematic illustration of a vacuum extraction system for removing excess coating material from a rotor core.

Figure 1 is a top plan view of a rotor sheet 10. The sheet 10, for example, is cut from a steel sheet (not shown) and has a generally circular shape. The lamination 10 contains a central rotor shaft opening 12 and a plurality of spaced apart and radially disposed openings 14 adjacent an outer periphery 16 of the lamination 10.

Figure 2 is a perspective view of a substantially cylindrical rotor core 20. The rotor core 20 is formed by stacking a plurality of laminations 10 at a height of, for example, between 25 and 150 min (between 1 and 6 inches). Each rotor shaft opening 12 of each lamination 10 is coaxially aligned with other rotor shaft openings 12 of other core laminations 10 to form a rotor shaft bore 22. The radially disposed openings 14 of each rotor lamination are aligned to form slots 24 for rotor rods. The number of slots 24 for rotor bars can vary depending on the desired number of rotor bars. If the laminations are skewed, as is well known in the art, the rotor bars 24 will be angularly offset with respect to the axis of the rotor shaft 22. The laminations 10 can be welded, interlocked or held together temporarily using a temporary tool, such as spring pins, to form the rotor core 20. Figure 3 is a flow chart illustrating a sequence of process steps 30 for forming a highly resistive film on the surfaces of the laminations 10 at the outer periphery of each rotor core slot 24 20 While the method 30 is described below with respect to the rotor core 20, it should be understood that a film could be formed on each lamination 10 separately. In addition, the film could be formed on other surfaces other than just the lamination slot surfaces using method 30.

Referring particularly to Figure 3, once the operations have started (step 32), the core 20 is cleaned (step 34). The rotor core 20 can be cleaned for example, using known and commercially available radio frequency heater equipment. With such equipment and at a frequency of 500 Hz, for example, the core 20 is heated to about 190 ° C for less than a minute. The core 20 does not necessarily need to be cleaned if the coating material adhered to the core surfaces without cleaning.

After the core 20 is clean, a coating material is applied (step 36) to the sheet metal surfaces at the outer periphery of each slot 24 along the entire length of the slot. During the coating process, the core 20 is preferably at a temperature of about 20 to 40 ° C. the coating material can be applied, for example, using injection or rolling methods described herein in greater detail.

After the application of the coating material, the core 20 is dried (step 38) and the coating material is polymerized (step 40). Such drying and curing steps (steps 38

can be performed using a controlled air convection oven to heat the core 20 to a temperature of about 100 to about 120 ° C for a time of about 10 to 15 minutes, to dry (step 38) and then heat the core 20 to about 300 ° C for at least 20 minutes, to harden (step 40) the coating material. After drying and hardening (steps 38 and 40), procedure 30 is complete at step 42.

Method 30 provides the advantage that long and energy-intensive annealing operations are eliminated. Also, using method 30, a substantially uniform film is formed on the selected rotor core surfaces.

With respect to the coating material applied in step 36, and in one embodiment, such material is of the following blend.

The particular percentages set forth above are percentages for a particular embodiment of the coating material. Close to each of those particular percentages is a range that exhibits an acceptable range of ingredient percentages for each ingredient. It should be understood, therefore, that the composition is not limited to the percentages specified for that embodiment.

The following are preferred directions for the. DAP, MAP and the colloidal silica mentioned above.

1 hour, 180 C)

An alkali-stabilized colloidal silica is unacceptable for use as colloidal silica for the mixture described above. Rather, the colloidal silica should be stabilized with ammonia.

The specifications in parentheses above have the following meanings. oH U% of solution at 25 ° C

This ingredient forms a 1% aqueous solution and when heated to 25 ° C. the solution has the indicated pH.

Solubility g / 100g of water.

The present ingredient is added, incrementally, to 100 g of water heated to 20 ° C. The water is completely saturated when the indicated number of grams of ingredients has been added to the water.

Solid content% (0.5g. 1 hour, 180 ° C)

0.5g of these ingredients is placed on an aluminum plate and heated for one hour at a temperature of 180 ° C. The percentage indicated is the percentage, by weight, of the solid material that remains after such heating.

Specific weight

The quantity indicated is the specific weight of the ingredient measured according to the ASTM D333 test method in g / cm <3>

For mixing the ingredients described above, and in one embodiment, the DAP and MAP are first dissolved in water. Up to 25% of the total percentage composition of water, as set forth above, i.e. 73.4%, can be used to predissolve such ingredients. After the complete solubilization of the DAP and MAP, colloidal silica is added to the mixture. The remaining amount of water is then added. The finished mix specifications are shown below.

mesh (44 microns)

The finished mixture would be uniform, and free from gel particles and foreign material.

By hardening the present coating material, as described in step 40 of Figure 3, the sulfate is forced to decompose and form a polyphosphate film on the surfaces of the laminations. The elemental composition of the film, according to the realization of material specified above is:

Using method 30 (Figure 3) with the coating material described above, the increase in rotor performance is facilitated because the resulting film has a high resistance to current flow and provides good mechanical separation between the rotor core and the rotor faunas. In addition, the coating material described above is believed to have the following desirable properties or characteristics: good adhesion to steel, dispersion stability at the required concentration for coating uniformity, thixotropy to prevent sagging and drying after application, transparent coloring. and inhibition of separation of the binder from the charge by drying.

Figure 4 is a schematic, partial sectional illustration of an example of an injection tool 50 which can be used to apply the coating material (step 36) of Figure 3) into slots 24 of rotor rods of the rotor core 20 The injection tool 50 contains an upper coating injection tool 52 and a lower coating injection tool 54. The upper tool 52 contains an external sealing ring 56 and an internal sealing ring 58. The coating charities 60 and 62 are formed in the upper tool 52 for air discharge. An air discharge, or suction, channel 64 is also formed in the upper tool 52 in communication with the cavity 60. In addition, the upper tool 52 contains a coating material detection channel 66 and an opening 68 in communication with cavity 60.

The lower tool 54 contains an external sealing ring 70 and an internal sealing ring 72. The tool cavities 74 and 76 are formed in the lower tool 54 to receive coating material. A supply channel 78 of coating material is also formed in the lower tool 54 in communication with the cavity 76.

In operation and after cleaning the rotor core 20, as described above for the cleaning step 34 (Figure 3), the rotor core 20 is positioned between the lower and upper tools 52 and 54. The tools 52 and 54 are then tightened against the rotor core 20 so that the sealing rings 56 and 58 of the upper tool 52 and the sealing rings 70 and 72 of the lower tool 54 form seals with the respective surfaces of the lower tool. core 20. The positions of the formed seals of the sealing rings 56 and 58, for example, are illustrated in Figure 5, which is a top view of the rotor core 20. The seals are formed at the positions of the sealing rings 56 and 58 as shown in Figure 5. Such seals conveniently prevent the coating material from being applied, for example, to the surfaces of laminations at the outer periphery of the bore 22.

Once the upper and lower tools 52 and 54 are clamped against the rotor core 20 as described above, the coating material is injected, under any suitable pressure, into the coating material supply channel 78. This injected material flows through the channel 78 and into the cavities 74 and 76. The coating material also flows into the slots 24 of the rotor bars, and part of the material flows into the discharge cavities 60 and 62 in the upper tool 52. The injected material may displace a portion of air initially in the tool 50 or the slots 24 of rotor rods, and such displaced air may be pushed through the exhaust channel 64 into the upper tool 52.

The amount of coating material required to be injected into the tool 50 can be empirically determined using any particular type of rotor core.

Alternatively, a level detector can be placed on the opening 68 to detect the level of coating material in the discharge cavity 60. In particular, when the material fills the cavity 60, some of the material will be diverted through the channels 66 to the opening. 68. By detecting the arrival of the material at the opening 68, the level of the coating material in the fixture 50 can be easily determined. In general, the amount of material injected is chosen to be a minimum amount required to ensure that the surfaces of the laminations at the outer periphery of each slot 24 of the rotor core 20 have been coated.

Rather than using the injection tool 50, other methods of applying coating material (step 36 of Figure 3) to the laminated material at the outer periphery of the rotor rod slots 24 of the rotor core 20 include vacuum filling and rolling. In the case of the vacuum filling process, suction is used to pull the liner material through the slots 24. In a rolling process, a mass of liner material is formed in an open tray or similar container. The rotor core 20 is then rolled through the mass so that the coating material fills the slots 24 of the rotor rods. The level of material in the tray is chosen so that the material completely occupies the slots 24 in the rotor bars when the rotor core 20 is rolled through the mass.

After applying the coating material to the laminated material at the periphery of the rotor rod slots 24, the excess coating material is allowed to drain from the core 20. Such excess coating material can be removed from the core using, for example, a extractor for aspiration.

Figure 6 schematically illustrates an exemplary embodiment of a vacuum extractor system 100 for removing excess coating material from the rotor core 20. The system 100 includes an upper suction tool 102 and a lower suction tool 104. The upper suction tool 102 contains a vacuum cavity 106 and a vacuum opening 108 in communication with a suction sleeve 10 connected to a suction motor (not shown). Similarly, a lower vacuum tool 104 contains a vacuum cavity 12 and a vacuum opening 14 in communication with a suction sleeve 16 connected to a vacuum motor (not shown). The opening 108 of the upper vacuum tool is not aligned with the opening 1 14 of the lower vacuum tool to avoid excessive removal of material.

In operation, the rotor core 20 is supported, for example, on a conveyor (not shown) or is held in a robotic clamping tool (not shown) and is conveyed between tools 102 and drives the vacuum motor and the material of Excess coating is extracted from the ends of the core 20 and into the vacuum cavities 106 and 112. Such excess material flows through the sleeves 110 and 116 to a collecting tank (not shown) for reuse.

Obviously, the injection equipment 50 and the suction system 100 are not necessarily limited to construction with the coating material described above. Such equipment 50 and system 100 could be used with several other coating materials. For example, the coating material generally known as C 5 or C6 type coreplate (indications from the American Iron and Steel Institute (A ISI)). such as the pure red "coreplate", available from P.D. George Company of St. Louis. Missouri, USA, could be injected into a rotor core by equipment 50 and the suction system 100 could be used to remove excess material.

From the previous description, it is evident that the purposes of the invention have been achieved. Although the invention has been described and illustrated in detail, it must be clearly understood that it is intended as a way of illustration and example only and should not be taken as a limitation. For example, rather than applying the coating material to the laminations after the rotor core has been formed, the method described above could be used to apply the coating material to each rotor lamination separately before forming the rotor core. Consequently, the spirit and / field of the invention must only be limited by the terms of the attached claims.

Claims (23)

CLAIMS 1. Method (30) for coating at least a preselected surface of at least one rotor lamination (10) for an electric motor, said method (30) comprising the steps of: applying (36) a coating material to the selected surface of the rotor lamination (10); drying (38) the rotor lamination (10); And harden the investment material (40). 2. Process (30) according to claim 1. wherein before applying (36) the coating material, said process (30) comprises the step of putting (34) the rotor lamination by induction heating the lamination to at least 190 ° C for less than about a minute. Process (30) according to claim 1, wherein the coating material (36) is applied while the sheet temperature is between about 20 and about 40 ° C. 4. Process (30) according to claim 1, in which the selected surface of the lamination (10) is the surface of the lamination at the outer periphery of the at least one slot (24) of rotor bars. Method (30) according to claim 1 wherein the application (36) of the coating material comprises the steps of placing the rotor lamination (10) in an injection equipment (50) and injecting the coating material in the slots (24) of the rotor lamination. 6. Process (30) according to claim 1, in which the application (36) of the coating material comprises the step of rolling the rotor sheet (10) through a mass of coating. Method (30) according to claim 1, wherein drying (38) of the rotor lamination (10) and curing (40) of the coating material comprises the steps of heating the lamination (10) to a temperature from about 100 to about 120 ° C for a period of about 10 to about 15 minutes and then heat the lamination (10) to about 300 ° C. Method (30) according to claim 1, wherein the coating material is coreptaie. Process (30) according to claim 1, wherein the coating material is diammonium phosphate (DAP), monoammonium phosphate (MAP) and ammonia stabilized colloidal silica. Process (30) according to claim 9, wherein the elemental composition of the polymerized material has a phosphate percentage of about 75% and a SiO2 percentage of about 25%. 1 1. A process (30) according to claim 1 wherein the coating material is composed of about 5.2% to about 12.5% diammonium phosphate, about 2.7% to about 8 % monoammonium phosphate and about 7.0% to about 12.0% colloidal silica. The method (30) of claim 1, wherein a plurality of laminations (10) are assembled to form a rotor core (20) and the coating material is applied to a plurality of lamination surfaces of the core (20) to an outer periphery of a plurality of rotor rod slots (24). 13. Aqueous solution, including: between about 5.2 and 12.5% by weight of diammonium phosphate; between about 2.7 and about 8.0% by weight of monoammonium phosphate; and between about 7.0 and about 12.0% by weight of ammonia stabilized colloidal silica. 14. Solution according to claim 13, in which said diammonium phosphate has a pH of approximately 8.0 at a solution substantially of 1% heated to substantially 25 ° C. has a colorless, granular and solid appearance, has a solubility in substantially 100 g of water at substantially 20 ° C of about 58 g and has a percentage of solid parts content, for about 0.5 g heated for about an hour at about I 80 ° C by about 75%. 15. Solution according to claim 13. in which said monoammonium phosphate has a pH of about 4.5 at a solution of about 1% heated to about 25 ° C, has a substantially colorless, granular and solid appearance, has a solubility in about 100 g of water at about 20 ° C of about 38 g and has a percentage content of solid parts, for about 0.5 g heated for about one hour at about 180 ° C of about 85%. 16. Solution according to claim 13. in which said colloidal silica stabilized by ammonia has a pH in a solution of about 1% heated to about 25 ° C of about 9.3. it has a substantially colorless, translucent and liquid appearance and has a specific weight of about 1.293 g / cm2 and has a percentage of solid parts content, for about 0.5 g heated for about an hour at about 80 ° C of about 17. Solution according to claim 13, wherein said solution has a solid percentage content, for substantially 0.3 g heated for about one hour at substantially 180 ° C of about 17%, a pH of about 6, 2, a specific weight of about 1.13 g / cm <3> and a phosphate percentage of about 12.5%. 18. Solution according to claim 13. in which said solution is composed of substantially 8.0% of diammonium phosphate, substantially 8.0% of monoammonium phosphate and substantially 10.6% of colloidal silica. 19. Apparatus (50) for injecting coating material into slots (24) of rotor rods of a rotor core (20), said apparatus (50) comprising an upper coating injection tool (52) and a lower tool of coating injection (54), said upper tool (52) comprising an outer sealing ring (56) and an inner sealing ring (38), at least one tool cavity (60, 62) positioned in said upper tool (52) , said lower tool (54) comprising an outer seal ring (70) and an inner seal ring (72). at least one fixture cavity (74, 76) positioned in said lower tool (54) for receiving coating material. Apparatus (50) according to claim 18, wherein said lower tool (54) further comprises a coating material supply channel (78) in communication with said lower tool cavity (76). Apparatus (50) according to claim 18, wherein said upper tool (52) comprises an air discharge channel (64) in communication with said upper tool cavity (60). 21. Apparatus (50) according to claim 18, wherein said upper tool (52) and said lower tool (54) are configured to be clamped against the rotor core (20) so that said sealing rings (56, 58 ) of said upper tool (52) and said sealing rings (70, 72) of said lower tool (54) form seals with respective surfaces of the core (20). 22. Apparatus (100) for removing excess coating material from a rotor core (20), said apparatus (100) comprising an upper suction tool (102) and a lower suction tool (104). said upper suction tool (102) comprising a vacuum cavity (106) and a vacuum opening (108), said lower suction tool (104) comprising a vacuum cavity (112) and a vacuum opening (114) ). said upper suction tool opening (108) and said lower suction tool opening (114) being spaced apart so that the rotor core (20) can be moved therebetween. 23. Apparatus (100) according to claim 22, wherein said upper suction tool opening (108) and said lower suction tool opening (114) are not axially aligned,