CA1288726C - Process for electrodepositing mica on coil or bar connections and resulting products - Google Patents
Process for electrodepositing mica on coil or bar connections and resulting productsInfo
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- CA1288726C CA1288726C CA000493348A CA493348A CA1288726C CA 1288726 C CA1288726 C CA 1288726C CA 000493348 A CA000493348 A CA 000493348A CA 493348 A CA493348 A CA 493348A CA 1288726 C CA1288726 C CA 1288726C
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Abstract
PROCESS FOR ELECTRODEPOSITING MICA ON COIL
OR BAR CONNECTIONS AND RESULTING PRODUCTS
ABSTRACT OF THE DISCLOSURE
A process for electrodepositing mica and a water soluble anionic resin binder, such as a modified polyester resin, is disclosed as a means for applying a heavy coating of a high-voltage, mica-bearing electrical insulation onto uninsulated and insulated portions of electrical connections in dynamoelectric machines. The electrodeposited mica coating is subsequently impregnated with a suitable resin, such as an epoxy or polyester resin, concurrently with the impregnation of other conventional insulations in the machine. Alternatively, deposition and impregnation of the connection insulation can be performed prior to installing the connection into the machine.
OR BAR CONNECTIONS AND RESULTING PRODUCTS
ABSTRACT OF THE DISCLOSURE
A process for electrodepositing mica and a water soluble anionic resin binder, such as a modified polyester resin, is disclosed as a means for applying a heavy coating of a high-voltage, mica-bearing electrical insulation onto uninsulated and insulated portions of electrical connections in dynamoelectric machines. The electrodeposited mica coating is subsequently impregnated with a suitable resin, such as an epoxy or polyester resin, concurrently with the impregnation of other conventional insulations in the machine. Alternatively, deposition and impregnation of the connection insulation can be performed prior to installing the connection into the machine.
Description
7;~6 PROCE5S FOR ELECTRODEPOSITI~G MICA ON COIL
OR BAR CONMECTIO~S AND RESULI'I~G PRODUCTS
Field of the Invention -The present invention relates generally to the art of electrophoretic disposition, and is more particularly concerned with a novel process for electrodepositing micaceous insulating coatings on end connections for electrical conductors, especially end connections for electrical coils and the like, and with he resulting novel insulated articles and assemblies.
Backyround of the Invention The connections in a small dynamoelectric machine are typified by the lengths of bare copper wires which join the stator coils in electric motors to each other and to external motor terminals.
Insulation of those small connections is usually accomplished by application of micaceous insulatiny tape after the connections are made from a few strands of wire and fastened together, for example, by bra~ing. Because in many cases, the actual connection is only several inches long, has an irreyular geometry, and is located in crowded part of the machine, the insulation normally has to be applied manually, a very slow and laborious processO
In larger machines, such as hydroelectric or ~: . ........ .. .. . ..
OR BAR CONMECTIO~S AND RESULI'I~G PRODUCTS
Field of the Invention -The present invention relates generally to the art of electrophoretic disposition, and is more particularly concerned with a novel process for electrodepositing micaceous insulating coatings on end connections for electrical conductors, especially end connections for electrical coils and the like, and with he resulting novel insulated articles and assemblies.
Backyround of the Invention The connections in a small dynamoelectric machine are typified by the lengths of bare copper wires which join the stator coils in electric motors to each other and to external motor terminals.
Insulation of those small connections is usually accomplished by application of micaceous insulatiny tape after the connections are made from a few strands of wire and fastened together, for example, by bra~ing. Because in many cases, the actual connection is only several inches long, has an irreyular geometry, and is located in crowded part of the machine, the insulation normally has to be applied manually, a very slow and laborious processO
In larger machines, such as hydroelectric or ~: . ........ .. .. . ..
2~
17M~ 3181 ~}~
steam turbine-generators, connections are often made using large copper tubes or bars. These connecting parts may be taped and impregnated prior to installation. In any case, however, because of the irregular shapes involved, much or all of the work must be done by hand.
A less complicated, yet effective technique of applying micaceous insulation, without the need for taping, would be of great benefit in the manu~acture of dynamoelectric equipment. In addition to savings in labor and time, the cost of materials could be substantially reduced because insulating tape production involving mica paper fabrication, lamination, etc., would be avoided. Also, less expensive wet ground mica might be used instead of the fluid-split or calcined mica required for tape manufacture.
Heretofore, electrodeposition of mica has been a recognized means of providing an electrical insulation coating or covering. m us, Shibayama et al, United States Patent No. 4,058,444 which issued November 15, 1977 discloees such a process for providing insulation for coils of rotary machines, mica and a water dispersion varnish being used in a coating bath formulation. Other patents describe the electrophoretic deposition of mica with the use of water dispersion resins in similar manner to bind the deposited mica particles. Japanese patents issued to Mitsubishi Electric Corp. (Japanese Patents Nos. 77 126438; 81 05,868 and 81 05,867) are directed along this same line, but none of them disclose the in situ electrodeposition of mica on electrical connections.
German Patent 1,018,088 issued to H. W. Rotter described the use of electrodeposited mica for insulating electrical connections, and sets ,, forth a coating bath formulation which contains extremely finely divided mica ( ' 1 micron). In addition, the possibility of using a silicone resin emulsion to aid in binding the flakes of mica together is mentioned.
oth cr ; 4~he applications of electrodeposited mica appear in the patent literature which involve the use of a binder either in the form of a water dispersion polymer or an aqueous emulsion. Objects to be coated such as wi.res, plates, and perforated plates are mentioned.
None of these prior art procedures have proven to be satisfactory enough to displace the manual technique with all of its drawbacks. For one reason~ the resultant coating compositions are unable to withstand conditions of the manufacturing environment, coalescing or coagulating when agitated or allowed to stand for prolonged periods.
Additionally, the emulsions and dispersions used heretofore result in coatings which are not of uniform thickness, particular on irregularly shaped conductor substrates because the different levels of electrical field strengths cause corresponding variations in insulating coating thickness.
The generally recognized, long-standing demand for answers to these problems, having not been met through any of the concepts disclosed in the foregoing patents or elsewhere in the patent art, has persisted to the present time.
Summar~ of the Invention By virtue of the present invention which is predicated upon the discoveries and concepts set out below, the shortcomings of the prior art can be avoided and new results and advantages can be obtained. Further, these gains can be made and realized without penalty of offsetting disadvantages of economy or efficiency or production, or of product quality, utility or volume.
A key concept underlying this invention, as well as the invention of United States Patent Number 4,533,694 Elton et al issued August 6, 1985 is to use in producing by electrodeposition thick (greater than 50 mils) insulation coatings, a ~3~ ` formulation in which the binder ~ contained in ~,;,,..,. J j` r~S
solution rather than being dispersed or emulsified in the liquid vehicle of the deposition formulation.
When such a solution is employed instead of a dispersion or emulsion of the prior art, the problem of thick and thin spots in the electrodeposited mica coatings is minimized as coatings of substantailly more uniform thickness are consistently produced.
Apparently, this is the result of self-limiting effect arising from the fact that depositions on a conductor from a coating bath containing mica and a water soluble binder result in the conductor becoming increasingly passivated which in turn results in decay of the deposition rate exponentially with time. The decay constant of this system, which determines how rapidly this effect develops, can be controlled by varying the concentration of water soluble binder and/or electrolyte in the coating bath. Thus, the high field strength areas of the conductor will beyin to accumulate a heavier coating than the low field regions, but will also more quickly become passivated. The low field strength regions do not become passivated as quickly and, consequently, will continue to acquire a coating at an increasingly greater relative rate than the higher field strength regions. More uniform coating thickness is the result.
It has been further found that coating quality can be enhanced and coating deposition rate can be controlled by adding a relatively small arnount .
7~
17MY 31~1 of an electrolyte to the aqueous coating bath.
As set foxth in the aforesaid referenced ` United States/Patent, the water soluble resin binder must have anionic functionality, that is, only anionic polymers are useful for my purposes and are therefore contemplated by the appended claims. Cationic or nonionic water soluble polymers, unlike anionic-type polymers, are not compatible with mica electrodeposition formulations because they ar~ not attracted to the anode with the mica which in water dispersion acquires a net negative charge.
Water soluble anionic resins having special utility in this invention are polyesters, epoxyesters, acrylics and carbo~y-terminated butadiene/acrylonitrile resins. It will be understood, however, that others may be used together with or in place of these, and that typically such a resin has an acid number (indicating carboxy group content) from 20 to 120 and that it is rendered water soluble by reaction with a substituted amine or other suitable base.
Still another concept of the invention is to impregnate the porous, dry, micaceous coating resulting from the electrodeposition from the ~eou8 mica containing bath. Thus, with the mica flakes being held together as deposited as a coating, resin varnish is applied to th~ coating and the impregnated coating is baked to cure the re~in varnish.
I have further discovered that when t'he process of this invention is carried out on a conductor which is insulated as by tape wrapped over a portion of the conductor length, the uninsulated bare portion and the immediately adjacent part of the conductor are covered with a continuous crack-free coating of electrodeposited insulating material. This discovery led me to the novel concept of insulating the series lead~ of motor coil assemblies by the process of immersing the bare lead portions and adjacent insulated lead portions in an electrodeposition bath and then electrodepositing a coating of insulating material on not only the bare exposed coil connection parts of the assembly, but also on the adjacent insulated parts thereof to provide overlapped insulation at each coil end connection~ A related new concept oE mine is to apply insulation to other electrical conductor components of dymanoelectric machines such as pole jumpers for hydrogenerators and similar equipment in which high integrity of the insulating cover material is essential over the full length of the conductor component and its connections.
Briefly stated, then, in its process aspect the present invention generally comprises the sequential steps of immersing bare electrtical connections and/or terminals between an end portion of a wire member in coil form or otherwise and another conductor in an aqueous electrodeposition composition containing mica particles, a water soluble anionic resin binder, an electrolyte and a nonionic surfactant; electrodepositing a coating from the bath on the bare electrical connections to provide a micaceous coating which, when dried, is porous and contains sufficient binder to hold the particles together in place on the substrate; next, the porous coating is impregnated with resin varnish; and finally the impregnated coating is heated to an elevated temperature to cure the resin varnish. This procsss accordingly is a new combination of procedural steps including the new step involving the use of the ~`~1 ~ew composition disclosed and claimed in the above-re-EerenceJpatent.
In more specific terms this new process 17M'~ 31~1 includes the preliminary step of wrapping a portion of the length of the conductor with insulating material, suitably in the form o~ tape, and immersing the so insulated part of the conductor and the uninsulatec1 adjacent part in the electrodeposition formulation, and then electrodepositing a coating of insulating material from the said formulation on the bar portion and on the immediately adjacent insulation-covered portion of the conductor to provide a continuous crack-free coating of high integrity.
In its product aspect this invention is in general the article or the assembly resulting from the application of the present novel process to electrical conductors generally and especially to those carrying an insulating cover over part of their lengths. Thus an electric motor assembly of insulated coils connected at their ends in series by coil leads which are in part bare and unin ulated as installed is provided with continuous crack-free insulation on each coil lead which overlaps and is bonded securely to the insulation on the coil lead as well as to the exposed metal surface thereof~
E3rief Description of the Drawi~
Those skilled in the art will gain a further and better understanding of this invention from the following detailed description of it, taken in conjunction with the drawi.ngs accompanying and forming a part of this speicification, in whi.ch Fig. 1 is a longitudinal sectional view of an electrical conductor wrapped with insulating tape over part of its length and covered with electrodeposited insulation by the method of this invention, the novel insulation overlap feature being readily apparent, Fig. 2 is a view like that o~ Fig. 1 of an electric motor series connection the lead portions of 17~Y 3L~1 ~ 8 --which are wrapped with insulating tape while the central or junction portion is covered by the electrodeposited insulation which overlaps and is securely bonded to the insulating tape;
Fig. 3 is a view in perspective o a four-coil formette of an electric motor stator with the coils and portions of the leads wrapped with insulating tape while bound connection portions of the leads are bare;
Fig. 4 is a perspective view o~ the formette of Fig. 3 after insulation has been electrodeposited in accordance with the process of this invention to provide continuous crack-free insulation covering the unwrapped portions and overlapping the wrapped portions of t~le coil leads; and, Fig. 5 is a partially diagrammatic sketch of an electrdeposition operation for applying insulating coatings to the bare portions of the series connections of an electric motor stator in accordance ~0 with preferred practice of this invention.
Brief Description of the Invention As illustrated in Fig. 1 a conductor in the form o~ a copper bar is provided with continuous, crack-free insulating cover 11 consisting of a combination of mica tape 12 wrapped around conductor 10 over a part of its length and electrodeposited mica insulation coating 13 covering and bonded directly to the unwrapped bare part of the conductor. As an important con~equence of electrodepositing insulation coatin~ 13 in strict compliance with the process of this invention as described above, the interface between the taped and bare parts o~ conductor 10 is covered by coating 13.
Thus the coating overlaps tape 1~, extending approximately as far beyond the said interface as the thickness dimension of coating 13 on the bare part of 17MY 31~1 the conductor. As shown, coating 13 is of substantially unifor~ thickness over the bare metal but tapers at about 45 from the interface to the end over tape 12~ Further, as indicated elsewhere herein, the thickness of coating 13 is largely a matter of the operator's choice as this invention enables electrodeposition o~ coatings of high integrity and uniformity of thickness 50 to 150 mils or more.
In the case of series connection 20 of Fig. 2 lead por*ion 21 is wrapped with mica tape insulation and the central or junction portion 22 is covered with a coating 24 of electrodeposited mica insulation. Again the insulation over the full length of connection 20 is continuous and crack-free because coating 24 bridges over the interface region between wrapped and bare parts of the series connection and is securely bonded to both. In this instance the overlap is appro~imately lO0 mils which is the thickness of coating 24 on the unwrapped or bare part of the element.
Coil formette 30 of Fig. 3 comprises four coils 31, 32, 33 and 34 and three series connections 35, 36 and 37. As in the case of series connection 20 of Fig. 2, these three are wrapped to some extent with the mica tape insulation which covers the four coils. The junctions of connections 35, 36 and 37 are not wrapped at the stage of assembly illustrated in this view.
Completion of the insulation system of the assembly of Fig. 3 is again accomplished in accordance with preferred practice of the process of this invention with the result shown in Fig. 4. Thus series connections 35, 3G and 37 of formette 30 are insulated by electrodeposited coatings 40, 41 and 42, respectively. Those coatings, like coating 24 on series connection 20, are each of substantially ~21E3~
uniform thickness about 100 mils and crack-free and c:ontinuous. Further, as a consequence of these coatings being formed as described above by an operation involving dipping of the formette in an electrodeposition bath of the kind specified herein, the ends of each coating have the geometry of coating 13 ofFig. 1, overlying the mica tape insulation and bridging across the interface between the taped and untaped parts of the series connection.
The dipping operation just mentioned is illustrated in Fig. 5 in which an electric motor stator 50 is suspended in coating vessel 52 with series connections 54 of the motor coils immersed in electrocoating solution bath 56. The dapth of this immersion is sufficient to insure that the tape insulation on the series connections is submerged to at least the extent that overlap of electrodeposited insulation is desired, then D.C. potential is applied to the system with vessel 52 serving as the ground and the power source suitably being a D.C. generator.
The compositional range of the electro-deposition bath in accord with the invention in weight percent is summarized below:
Component Broad Ranqe Preferred Ran~e Mica 5 - 35% 10 - 15%
Soluble Resin Binder 0.2 -2% 0.5 - 1.5 (as solids) Electrolyte 0.001 - 0.20% 0.002 - 0.05%
Nonionic Surfactant 0 - 0.3% 0.03 - 0.10%
30 Water Balance Balance The electrical connection or group of ~ ,. ~
: "
8~72~
17M~ 3181 connections to be insulated are coated by electrodeposition. The connection is immersed in the aforementioned bath. A direct current (D.C.) potential is applied to the conductor in the connection, typically in the range of ~20 to ~150 volts. Simultaneously, a grounded counterelectrode must be present in the bath. The mica flakelets in suspension are attracted to the anodic connection and are deposited there as long as current flows from it.
The organic binder also codeposits with the mica flakes. Typical deposition times range from 20 to 500 seconds, depending on the binder, electrolyte concentrations and the thickness of the insulation coating desired.
The interface betwe~n the electrodeposited mica and the taped insulation is the region of greatest difficulty in achieving a consolidated, crack-free insulation, due to the properties of the two dissimilar insulation materials. In some instances depending on the type of mica tape used, better adhesion, between the electrodeposited mica and the tape, can be accomplished when a nonionic surfactant, i.e., one that does not undergo migration in an electric field, is incorporated into the deposition bath. A typical nonionic surfactant is Tergitol NPX (alkyl phenyl e~her of polypropylene glycol), available from Union Carbide Corporation.
When enough mica has been deposited, the D.C. current is switched off and the connection is removed fro~ the bath. The initial wet coating on the connection is a composite of mica flakelets, binder solids and water. This coating is allowed to dry at a temperature greater than 0C and less than 100C, but preferably from about 25C to about 75C. l'he residual water is baked out in an oven at an elevated temperature. At the same time the elevated ... - .,. . ~, temperature serves to cure the binder~ The result is a dry, micaceous coating which is porous and contains enough binder to hold the mica flakes together.
The next step is a post-impregnation treatment of the porous coating, in which the connection is either dipped into an impregnating varnish or, more preferably, treated by vacuum-pressure impregnation with a suitable epoxy or polyester resin. This impregnation treatment can, in many instances, be part of the same cycle whereby other conventional insulations in the dynamoelectric machine are also being resin treated~ Frequently in the actual dynamoelectric machine there are two such post impregnation treatments.
The final step consists of an elevated temperature bake to cure the impregnated resin.
Generally, the curing step includes heating to a temperature of 150 to 180C for a time of four to si~
hours. Longer curing times can be used, but are usually not necessary. ~he higher the temperature the shorter the time required for a satisfactory cure. A
typical curing step is at a temperature of 160C for a time of six hours.
The resulting prvduct is a micaceous connection insulation, consolidated and void-free.
This procedure has the advantages of using low-cost mica and elminating all taping operations in the connection region. In instance~ in which a wire or coil terminal is to be connected to a wire or coil and then used as a connector, it may be kaped over initially with a suitable tape and after the plating process is complete the underlying tape and the insulation deposited thereover may be removed.
The invention is further described by the following examples in which all mesh is given in U.S.
Standard sieve siæes and all percentayes are given in 17~Y
weight percent.
Example I
A representative model of a conventional high-voltage motor coil connection was made by overlapping two rectangular copper strips about 1/2"
and brazing them together. This joined connection was then bent in the shape of a "U", and insulated with conventional mica tapes on the ends only. To insulate ths bare copper portion, the connection model was immersed in a metal vessel containing a bath of the following composition: 900 grams of 325 mesh wet ground muscovite mica powder; 170 grams o~ a water soluble polyester resin varnish, available as Sterling WS-200 WAT-A-VAR, from Reichold Chemicals, Inc.; 2 grams of ammonium nitrate electrolyte, and enouyh distilled water to bring the volume up to 2 gallons.
The model was immersed in the bath for a period of 2 minutes to eliminate air from the submerged taped insulation portion. Using a metal vessel as the ground, an anodic potential of 60 volts D.C. was applied for 350 seconds to deposit the mica and binder. Thereafter the model was dried for 15 hours at 25C and baked 6 hours at 160C. It was subsequently vacuum-pressure impregnated with an accelerated version of an epoxy resin consisting in weight percent of about a 60~-~y ~ and 40%
a liquid Bisphenol A-diglycidyl ether epoxy, as disclosed in Markovitz United States Patent Number 3,812,214 which issued May 21, 1974.
Thereafter, the epoxy was cured 6 hours at 160~C.
The result was the deposition of a smooth, uniform inuslation/ about 125 mils thick, coating the bare portion, and two overlapping portions that rise over the conventionally taped insulation by about 120 mils. The mica content of the coating was determined to be 36.9~. The two overlapping portions between the electrodeposited and conventional insulation werc wrapped with a 2" metal foil, and when subjected to electrical testing, it was found that over 35,000 volts at 60 Hz were applied, between the copper strips and foils, without failure of the insulation.
Example II
A high-voltage connection model was prepared from a rectangular copper strip by insulating half of its length with conventional mica tape. The following bath was prepared for coating the bare copper portion of this strip: 7,500 grams of 325 mesh wet ground muscovite mica powder; 900 grams of a water soluble polyester varnish, available as Aquanel 513 from Schenectady Chemicals, Inc~; 17 grams of basic aluminum acetate (stabilized with boric acid); 7 grams of ammonium nitrate, and enough distilled water to bring the volume up to 32 liters.
The model was immersed for several minutes to eliminate air from the taped insulation, and then an anodic potential of 60 volts D.C. was applied for 105 seconds. The model was then removed and dried at 25C overnight, and baked 6 hours at 160C. It was subsequntly vacuum-pressure :impregnated with an epoxy resin as described in Example I, and cured for 6 houxs at 160~C.
The result was a uniform void-free micaceous insulation about 200 mils thick, and overlapping the upper portion of the mica tape insulation by about 200 mils. A metal foil was wrapped over the interface, and electrical failure did not occur until a potential of 40,000 volts at 60 Hz was reached.
Example III
A connection model for a large generator was prepared by soldering together 3 lenths of 1-1/8" oOd.
copper tubing in the shape of a "T".
A bath for coating this object was prepared ~2~
as follows: 5,600 grams of 325 mesh wet ground muscovite powder; 560 grams of Aquanel 513 soluble polyester varnish; 17,5 grams o~ basic aluminum acetate (stabilizPd with boric acid), and enough distilled water to bring the volume up to 34 liters.
The "T" shaped object was then immersed in this bath, and an anodic potential of 60 volts D.C.
was applied for a period of 300 seconds. I'hereater, the object was removed and allowed to dry at 25C
for 24 hours. It was then baked 6 hours at 160C, and subsequently impregnated with the epoxy resin, as and according to the procedure described in Example I.
The final cure was for 6 hours at 16QC.
This process resulted in a uniform micaceous insulation on the outside surface of the copper tubing which was about 75 mils thick and contained about 35 mica. When the region about the corners of the "T"
were wrapped with metal foil, voltage was applied up to 25,000 volts without failure.
Example IV
A multiple coil motor model, known as a formette, was constructed using 4 motor coils placed in a fixture similar to the stator of a high-voltage motor. These coils were insulated with conventional mica tapes and wrappers, except for the leads, which consisted of bundles of six bare rectangular copper wirer The leads were joined in series from one coil to the next by brazing, resulting in 3 bare seri~s connections. A bath for electrodeposition of mica onto these leads was prepared by mixing the following constituents: 1,800 grams of 325 mesh wet ground muscovite powder; 3~0 grams of Sterling WS-200 WAT-A-VAR water soluble polyester varnish; 4 grams ammonium nitrate electrolyte, and enough distilled water to bring the volume up to ~ gallons.
The end region of the formette was immersad ~ ~8~
in the bath so that all of the bare copper connections were submerged. An anodic potential of 70 volts D.C.
was applied for 270 seconds. Thereafter the formette was removed, dried at 25C for 24 hours, and then baked for 6 hours at 160C. Following this, the electrodeposited insulation along with the conventional taped insulation was impregnated with an epoxy resi~ as disclosed in Example I. I~e resin was then cured for 6 hours at 160C.
The result was a continuous insulation around the coil connections about 110 mils thick and overlapping the taped insulation by about 100 mils.
Example V
Three high-voltage motor connection models were prepared by bending 15" copper strips in the shape of a "U", and insulating the ends with mica tapes, similar to the method described in Example I.
A coating formulation was prepared in a metal vessel by mixing the following consituents: 900 grams of 325 mesh wet ground muscovite mica powder; 170 grams of Aquanel 550 water soluble polyester varnish; 2 grams of ammonium nitrate; 4 grams of Tergitol NPX nonionic surfactant available from Union Carbide Corporation, and enough distilled water to bring the total volume up to 2 gallons.
The bare copper portion of each model was coated by immersing the model in the bath and applying an anodic potential of 60 volts D.C. for a period of 180 seconds. Thereafter, the objects were allowed to dry overnight at 25C, and then baked 6 hours at 160C. Following this, they were vacuum-pressure impregnated with an epoxy resin as described in Example I, and cured 6 hours at 160C.
The foregoing resulted in a smooth uniform micaceous insulation about 120 mils thick and overlapping the taped insulation by about 130 mils.
... .... .
8~7~
The insulation integrity was tested by applying 9000 volts at 60 Hz between the outside surface and the copper, and found to pass without failureO
Thereaftsr, the models were thermally cycled by repeatedly passing current through the copper to heat it to 190C, and subsequently permitted to cool in air to 30C. After 2000 such cycles, the models were tested by immersion in water containing a wetting agent for 30 minutes. The 4600 volts at 60 Hz were applied to the submerged samples without any dielectric failure occurring.
Example VI
Three high-voltage motor connection models were prepared as described in Example V. A coating formulation was prepared by mixing the following constituents in a metal vessel: 900 grams of 325 mesh wet ground muscovite mica powder; 170 grams of Aquanol 513 water soluble polyester varnish; 2 grams of ammonium nitrate; 4 grams of Tergitol NPX nonionic surfactant; and enough distilled water to bring the total volume up to 2 gallons.
The bare copper and insula~ed portions of each model were coated by immersing the model in the bath, and applying an anodic potential of 60 volts D.C. for a period of 140 seconds. Thereafter, the objects were allowed to dry overnight at 25C and then baked 6 hours at 160C. Eollowing this they were vacuum-pressure impregnated with an epoxy resin as described in Example I, and cured 6 hours at 160C.
This resulted in a smooth uniform micaceous insulation about 130 mils thick, and overlapping the taped insulation by about 130 mils. The insulation was tested by applying 9000 volts at 60 Hz as in Example V, without failure. These models were 35 thermally cycled from 190C to 30C for 2000 times as in Example V and tested at 4600 volts at 60 Hz under ., : . . :
~ . .
:
17M~ 3181 water after 30 minutes submersion, without ~ailure~
One model was then placed back on the thermal cycling test for an additional 3136 cycles, removed, and submerged under water. It passed the 4600 volt test.
ExamE~le VII
A formulation of the coating composition of the present invention was prepared by mixing the following ingredients; 5,600 grams of 88 mesh muscovite mica powder available from franklin Minerals, Inc., 560 grams Aquanel 513 water soluble insulating varnish available from Schenectady Chemicals, Inc. (28% solids of an oil modified polyester), 2.5 grams sodium chloride, and enough distilled water to bring the bath volume up to 34 liters.
A rectangular copper wire, .162" x .322"
cross section, was immersed in the coating formulation coaxial with respect to a 3 inch copper tube at ground potential. Mica and binder were electrodeposited on the wire by applying an anodic potential of 60 volts D~Co for 80 seconds. The coated wire was removed from the bath and dried at 25C for 15 hours, and the binder cured at 165C for 4 hours, resulting in a porous micaceous coating.
Thereafter, the coating was vacuum/pressure impregnated with an epoxy resin consisting of 60~
cycloaliphatic and 40% Bisphenol A epoxy, as disclosed in Markovitz, U.SO Patent 3,812,214. The epoxy was cured for 6 hours at 160C to yield a consolidated, 30 void-free insulation 30 mils thick containing 40.4%
mica. The insulation was voltage endurance tested by wrapping the insulated wire spirally with a 40 mil bare Cu wire and applying 7,500 volts at 60 Hz. m e insulation survived the corona and voltage stress for 5,035 hours.
17MY 31~1 Example VIII
Following the procedure of Example VII, a formulation was prepared consisting of 900 grams of 325 mesh muscovite powder, 200 grams of Aquanel 513 water soluble polyester varnish, 2 grams of ammonium nitrate, diluted to 2 gallons with distilled water and stored in a tin coated steel container.
A test sample was prepared from two parallel copper bars, having rectangular cross sections of 1 inch x 1/4 inch, and 6 inches in legnth. The bars were separated ~y two 3/8 inch thick phenolic spacers placed at either end of the bars and the bars were bolted together. The sample was then immersed in the coating formulation. Mica and binder were deposited thereon by applying an anodic potential of 100 volts D.C. for a time of. 400 seconds. The metal container was grounded and became the cathode of the electrical deposition system. The bars were removed and dried 15 hours at 25C, then 6 hours at 105C, and finally 6 hours at 160~F. Thereafterr the bars were vacuum/pressure impregnated with an accelerated version of the epoxy resin disclosed in Example I, and the resin cured at 160C for 6 hours. The resulting insulation measured 130-137 mils thick on the outside faces of the hars and 102-107 mils on the inner faces. This represents a reduction in insulation thickness of only about 15% in the electrically shielded region.
This example demonstrates how an improved uniformity of insulation build can be achieved in regions where electrical shielding or enhancement occurs simply by adjusting the concentration of water soluble binder.
As a comparison, the same copper bar configuration immersed in a bath containing the same constituents as in Example IV and 100 grams of .
.. . .. .
~.,, . .
.
:.
7~
T~ - 20 -Aquanel 513 instead of 200 grams results in insulation builds of 252 mils and 85 mils on the outer and inner aces, respectively. Here, a reduction in thickness of ~G% occurs in the shielded region.
ExamE~le IX
In order to compare the effects of using water soluble resins versus water dispersed resins in the electrodeposition of mica, test samples of two parallel copper bars (designated as bar X and bar Y) were prepared having th~ dimensions and configuration as described in ~xample VIIIo Electrodeposition baths were prepared consisting of 2 pounds of 325 muscovite, 2 grams of ammonium nitrate, 114 grams (on a solid basis) of resin and two gallons of distilled water.
The resin systems compared in the above formulation were as shown in the following table. In the subsequent discussion and tabulation of the experimental results, the electrodeposited samples are identified by the designation of the resin system used.
TABLE II
Resin System A. Water Soluble Resins Al. Aquanel 513, a water soluble polyester, commercially available from Schenectady Chemical Company.
A2. Aquanel 550, a water soluble polyester, commercially available from Schenectady Chemical Company.
T~
A3. GE 111-244, a water soluble polyester/
available from General Electric CompanyO
B. Water Dispersion Resins Bl. Rhople ~ TR-407, an acrylic dispersion resin, commercially available from Rohm and Haas Company.
~x~
B2. Rhoplex AC-1533, an acr~lic dispersion resin, commercially available from Rohm and Haas Company.
B3. Rhoplex AC-1822, an acrylic dispersion resin, commercially available from Rohm and Haas Company.
B4. CavaliteTM, an acrylic dispersion resin, commercially available from E.I. DuPont De Nemours and Company.
Mica and binder were electrodeposited on the wire by applying an anodic potantial of 80 volts D.C. for a time of 180 seconds with the exception that the time in sample B2 was I30 seconds and the sample B4 was 120 seconds.
In all cases the outer coating was thicker than the inside coating, due to an electrical shielding effect. In the case of water soluble resin coatings, improved thickness uniformity between the inside and the outside as indicated by the ratio of I/0 resulted. Water ; dispersion resins, on the other hand were much more in~luenced by the electrical shielding effect as indicated by a significantly lower ratio of I/0.
The results are shown in the following table:
~'"1 , , ''~ ' ,' , , ` ',: ", ,, ", ' :
,' ' ' ,"
' ~.2~
17M~ 3181 TABLE III
Resin System BarsInside Outside Ratio Thick-Thick- I/O
ness~ I ness, O
(mils)(mils) -A. Water Soluble Resins Al. Aquanel 513 X 70 98 .71 Y 7~ 99 .79 A2. Aquanel 550 X 57 98 .58 ~ 60 98 .61 A3. GE lll-244 X 80 102 .78 ~ 88 112 .79 5 B. Water Disper-sion Resin Bl. Rhoplex X 19 49 .39 ~ 19 52 .37 B2. Rhoplex X 42 135 .31 ~C-1533 Y 48 120 .40 B3. Rhoplex X 45 105 .43 Y 54 115 .47 B4. Cavalite X * * *
Y * * *
* Coating did not adhere to test bars and no measurements were possible.
Similar test bars to those used in the thickness test were also prepared, and subjected to a rinse under running water from a Eaucet.
Sample Al, A2 and A3 remained adherent to the bars.
Sample B4 could not be evaluated since it had insufficient adhesion to the bar. Sample B3 washed off easily. Samples Bl and B2 washed ofE partially, leaving exposed portions of copper, and reduced coating thicknesses in other places.
17~ 3181 E~ample X
The utility of water soluble expoxyesters in accoxdance with this invention was tested by prepariny a one gallon aqueous bath of the following ingredients:
l lb of 325 mesh ~ica llO grams Isopoxy 771 (Schenectady Chemicals~
1 gram N~14NO3 Z grams Tergitol NP10 surfactant A coppe~ bar was immersed in thi~ bath at room temperature and maintained at +60 volts for 240 ssconds whereupon the bar was removed, dried 24 hours at 25C and then baked 6 hours at 160C. The bar was then impregnated by vacuum pressure impregnation technique with an epoxy resin and then baked at 160 for 6 hours to cure the epoxy resin. The result was found to be a uniform coating of about 0.210 inch and was void free and of mica content approximating 40 percent. Thus, this coating compared favorably with that produced as described above in Example VII.
Example XI
The suitability of water soluble acrylics was similarly tested in another experiment in which a two gallon aqueous bath was prepared by adding the following to water:
2 lbs of 325 mesh mica 360 grams Acrysol~ S-68 acrylic resin (Rohm & Haas) 4 grams Tergitol NPlO 3urfactant 2 grams Sodium Lauryl sulfate 2 grams Dimethylaminoethanol Again, a copper bar was immersed in this bath and held at ~60 volt~ for 300 seconds whereupon the bar was removed and treated as in Example X with the consequence that a coating of uniform thickness approximating 0.200 inch was produced having a mi~a content of about 40 percent and being void free and comparing again favorably with the insulating coating . .
.
described above in Example VII.
Example XII
A one gallon aqueous bath was prepared by addiny the ollowing to water:
l lb. of 325 mesh mica;
65 grams Carboxy-terminated butadien0/acrylo-nitrile (B.F. Goodrich) 2 grams NH4N03 2 grams Tergitol NPlO
1 gram Sodium Lauryl sulfate This, thus, as a test of the suitability in accordance with this invention of the so called CTBN resins which are described above blended in 65 grams o butyl cellosolve and reacted with 4.6 grams dimethylaminoethanol to render them water soluble. As in Examples X and XI, a copper bar was immersed in this bath and held at 45 volts for 150 seconds then removed and processed as described in Example VIII
with the result that a uniform coating of about 0.12 inch thickness resulted. This insulating coating was found to be void free and to have a mica content approximating 40 percent and to be therefore quite similar to those of Example VII, VIII and IX above.
ExamE~le XIII
To test the suitability of combinations of the~e anionic water soluble resins for the purposes of this invention, a four gallon aqueous bath was prepared by adding Acrysol WS-68 and Aquanel 513 in a ratio to each other about 1.5 to l, the actual formulation being as follows:
480 grams Acrysol WS-68 acrylic resin 340 grams Aquanel 513 polyester rPsin 8 gram~ Tergitol NPID
4 grams Sodium Lauryl Sulfate 8 grams Dimethyl~amino-ethanol 5 grams Ammonium Nitrate and the balance water.
Once again, the copper bar test as described in Example VIII was carried out with successful results in terms of the resulting insulating coating being of uniform thickness approximating 0.21 inch and of mica content approximating 40 percent and being void free and altogether a superior electrical insulating coating of the sort described above in Example VII.
Example XIV
The utility of non-ionic polymer in this invention was tested in an experiment involving the use of l lb. of 325 mesh mica 75 grams of polyethyleneglycol (average mica weight 6,000) 1 gram of ammonium nitrate The mixture was added to one gallon of water and a copper bar test was run as described above in Examples X-XIII. Thus, the copper bar was immersed in this bath and a potential of 60 volts D.C. was applied for about one minute the bar being then removed and found to be completely clean. There was no mica adherence to the bar at all and the polymer was found of itself to be insufficient to hold the mica particles together.
r~
The stability of a cationic polymer was similarly tested in experiments which involved formulation of 1 lb. of 325 mesh mica 2 grams of NH~MO3 80 grams of Poly-2-vinylpyridine dissolved in 80 milliliters of butyl cellosolve 20 grams of acetic acid The mixture was prepared in a volume of one gallon with water and agitated for 30 minutes in a paint shaker to allow the ingredients to disperse and the acid to react with the Poly-2-vinylpyridine to form a ~L2~
17MY 31~1 polyelectrolyte. Then two copper strips were immersed in the bath spaced about two inches apart, the potential of 60 volts D.C. was applied to the strips.
Immediately mica was observed to begin accumulating about the anode while at the cathode a gelatinous accumulation was observed. After 60 seconds, the voltage was dropped to zero and the strips were removed. The mica deposit at the anode having no binder slipped off the wire and could not be removed from the bath, thus demonstrating the generic inability o~ cathodic deposition resins to bind or hold material deposited at the anode.
The data obtained from these tests substantiate the fact that in electrodeposition of mica improved results can be obtained using anionic water soluble resins as compared to water dispersion resins and to non-ionic and cationic water soluble resins.
In this specification and in the appended claims wherever percentage or proportion are stated, reference is to the weight basis unless otherwise specifically noted.
It will be appreciated that the invention is not limited to the specific details shown in the illustrations, and that various modif:ications may be rnade within the ordinary skill in the art without departing from the spirit and scope of the invention.
17M~ 3181 ~}~
steam turbine-generators, connections are often made using large copper tubes or bars. These connecting parts may be taped and impregnated prior to installation. In any case, however, because of the irregular shapes involved, much or all of the work must be done by hand.
A less complicated, yet effective technique of applying micaceous insulation, without the need for taping, would be of great benefit in the manu~acture of dynamoelectric equipment. In addition to savings in labor and time, the cost of materials could be substantially reduced because insulating tape production involving mica paper fabrication, lamination, etc., would be avoided. Also, less expensive wet ground mica might be used instead of the fluid-split or calcined mica required for tape manufacture.
Heretofore, electrodeposition of mica has been a recognized means of providing an electrical insulation coating or covering. m us, Shibayama et al, United States Patent No. 4,058,444 which issued November 15, 1977 discloees such a process for providing insulation for coils of rotary machines, mica and a water dispersion varnish being used in a coating bath formulation. Other patents describe the electrophoretic deposition of mica with the use of water dispersion resins in similar manner to bind the deposited mica particles. Japanese patents issued to Mitsubishi Electric Corp. (Japanese Patents Nos. 77 126438; 81 05,868 and 81 05,867) are directed along this same line, but none of them disclose the in situ electrodeposition of mica on electrical connections.
German Patent 1,018,088 issued to H. W. Rotter described the use of electrodeposited mica for insulating electrical connections, and sets ,, forth a coating bath formulation which contains extremely finely divided mica ( ' 1 micron). In addition, the possibility of using a silicone resin emulsion to aid in binding the flakes of mica together is mentioned.
oth cr ; 4~he applications of electrodeposited mica appear in the patent literature which involve the use of a binder either in the form of a water dispersion polymer or an aqueous emulsion. Objects to be coated such as wi.res, plates, and perforated plates are mentioned.
None of these prior art procedures have proven to be satisfactory enough to displace the manual technique with all of its drawbacks. For one reason~ the resultant coating compositions are unable to withstand conditions of the manufacturing environment, coalescing or coagulating when agitated or allowed to stand for prolonged periods.
Additionally, the emulsions and dispersions used heretofore result in coatings which are not of uniform thickness, particular on irregularly shaped conductor substrates because the different levels of electrical field strengths cause corresponding variations in insulating coating thickness.
The generally recognized, long-standing demand for answers to these problems, having not been met through any of the concepts disclosed in the foregoing patents or elsewhere in the patent art, has persisted to the present time.
Summar~ of the Invention By virtue of the present invention which is predicated upon the discoveries and concepts set out below, the shortcomings of the prior art can be avoided and new results and advantages can be obtained. Further, these gains can be made and realized without penalty of offsetting disadvantages of economy or efficiency or production, or of product quality, utility or volume.
A key concept underlying this invention, as well as the invention of United States Patent Number 4,533,694 Elton et al issued August 6, 1985 is to use in producing by electrodeposition thick (greater than 50 mils) insulation coatings, a ~3~ ` formulation in which the binder ~ contained in ~,;,,..,. J j` r~S
solution rather than being dispersed or emulsified in the liquid vehicle of the deposition formulation.
When such a solution is employed instead of a dispersion or emulsion of the prior art, the problem of thick and thin spots in the electrodeposited mica coatings is minimized as coatings of substantailly more uniform thickness are consistently produced.
Apparently, this is the result of self-limiting effect arising from the fact that depositions on a conductor from a coating bath containing mica and a water soluble binder result in the conductor becoming increasingly passivated which in turn results in decay of the deposition rate exponentially with time. The decay constant of this system, which determines how rapidly this effect develops, can be controlled by varying the concentration of water soluble binder and/or electrolyte in the coating bath. Thus, the high field strength areas of the conductor will beyin to accumulate a heavier coating than the low field regions, but will also more quickly become passivated. The low field strength regions do not become passivated as quickly and, consequently, will continue to acquire a coating at an increasingly greater relative rate than the higher field strength regions. More uniform coating thickness is the result.
It has been further found that coating quality can be enhanced and coating deposition rate can be controlled by adding a relatively small arnount .
7~
17MY 31~1 of an electrolyte to the aqueous coating bath.
As set foxth in the aforesaid referenced ` United States/Patent, the water soluble resin binder must have anionic functionality, that is, only anionic polymers are useful for my purposes and are therefore contemplated by the appended claims. Cationic or nonionic water soluble polymers, unlike anionic-type polymers, are not compatible with mica electrodeposition formulations because they ar~ not attracted to the anode with the mica which in water dispersion acquires a net negative charge.
Water soluble anionic resins having special utility in this invention are polyesters, epoxyesters, acrylics and carbo~y-terminated butadiene/acrylonitrile resins. It will be understood, however, that others may be used together with or in place of these, and that typically such a resin has an acid number (indicating carboxy group content) from 20 to 120 and that it is rendered water soluble by reaction with a substituted amine or other suitable base.
Still another concept of the invention is to impregnate the porous, dry, micaceous coating resulting from the electrodeposition from the ~eou8 mica containing bath. Thus, with the mica flakes being held together as deposited as a coating, resin varnish is applied to th~ coating and the impregnated coating is baked to cure the re~in varnish.
I have further discovered that when t'he process of this invention is carried out on a conductor which is insulated as by tape wrapped over a portion of the conductor length, the uninsulated bare portion and the immediately adjacent part of the conductor are covered with a continuous crack-free coating of electrodeposited insulating material. This discovery led me to the novel concept of insulating the series lead~ of motor coil assemblies by the process of immersing the bare lead portions and adjacent insulated lead portions in an electrodeposition bath and then electrodepositing a coating of insulating material on not only the bare exposed coil connection parts of the assembly, but also on the adjacent insulated parts thereof to provide overlapped insulation at each coil end connection~ A related new concept oE mine is to apply insulation to other electrical conductor components of dymanoelectric machines such as pole jumpers for hydrogenerators and similar equipment in which high integrity of the insulating cover material is essential over the full length of the conductor component and its connections.
Briefly stated, then, in its process aspect the present invention generally comprises the sequential steps of immersing bare electrtical connections and/or terminals between an end portion of a wire member in coil form or otherwise and another conductor in an aqueous electrodeposition composition containing mica particles, a water soluble anionic resin binder, an electrolyte and a nonionic surfactant; electrodepositing a coating from the bath on the bare electrical connections to provide a micaceous coating which, when dried, is porous and contains sufficient binder to hold the particles together in place on the substrate; next, the porous coating is impregnated with resin varnish; and finally the impregnated coating is heated to an elevated temperature to cure the resin varnish. This procsss accordingly is a new combination of procedural steps including the new step involving the use of the ~`~1 ~ew composition disclosed and claimed in the above-re-EerenceJpatent.
In more specific terms this new process 17M'~ 31~1 includes the preliminary step of wrapping a portion of the length of the conductor with insulating material, suitably in the form o~ tape, and immersing the so insulated part of the conductor and the uninsulatec1 adjacent part in the electrodeposition formulation, and then electrodepositing a coating of insulating material from the said formulation on the bar portion and on the immediately adjacent insulation-covered portion of the conductor to provide a continuous crack-free coating of high integrity.
In its product aspect this invention is in general the article or the assembly resulting from the application of the present novel process to electrical conductors generally and especially to those carrying an insulating cover over part of their lengths. Thus an electric motor assembly of insulated coils connected at their ends in series by coil leads which are in part bare and unin ulated as installed is provided with continuous crack-free insulation on each coil lead which overlaps and is bonded securely to the insulation on the coil lead as well as to the exposed metal surface thereof~
E3rief Description of the Drawi~
Those skilled in the art will gain a further and better understanding of this invention from the following detailed description of it, taken in conjunction with the drawi.ngs accompanying and forming a part of this speicification, in whi.ch Fig. 1 is a longitudinal sectional view of an electrical conductor wrapped with insulating tape over part of its length and covered with electrodeposited insulation by the method of this invention, the novel insulation overlap feature being readily apparent, Fig. 2 is a view like that o~ Fig. 1 of an electric motor series connection the lead portions of 17~Y 3L~1 ~ 8 --which are wrapped with insulating tape while the central or junction portion is covered by the electrodeposited insulation which overlaps and is securely bonded to the insulating tape;
Fig. 3 is a view in perspective o a four-coil formette of an electric motor stator with the coils and portions of the leads wrapped with insulating tape while bound connection portions of the leads are bare;
Fig. 4 is a perspective view o~ the formette of Fig. 3 after insulation has been electrodeposited in accordance with the process of this invention to provide continuous crack-free insulation covering the unwrapped portions and overlapping the wrapped portions of t~le coil leads; and, Fig. 5 is a partially diagrammatic sketch of an electrdeposition operation for applying insulating coatings to the bare portions of the series connections of an electric motor stator in accordance ~0 with preferred practice of this invention.
Brief Description of the Invention As illustrated in Fig. 1 a conductor in the form o~ a copper bar is provided with continuous, crack-free insulating cover 11 consisting of a combination of mica tape 12 wrapped around conductor 10 over a part of its length and electrodeposited mica insulation coating 13 covering and bonded directly to the unwrapped bare part of the conductor. As an important con~equence of electrodepositing insulation coatin~ 13 in strict compliance with the process of this invention as described above, the interface between the taped and bare parts o~ conductor 10 is covered by coating 13.
Thus the coating overlaps tape 1~, extending approximately as far beyond the said interface as the thickness dimension of coating 13 on the bare part of 17MY 31~1 the conductor. As shown, coating 13 is of substantially unifor~ thickness over the bare metal but tapers at about 45 from the interface to the end over tape 12~ Further, as indicated elsewhere herein, the thickness of coating 13 is largely a matter of the operator's choice as this invention enables electrodeposition o~ coatings of high integrity and uniformity of thickness 50 to 150 mils or more.
In the case of series connection 20 of Fig. 2 lead por*ion 21 is wrapped with mica tape insulation and the central or junction portion 22 is covered with a coating 24 of electrodeposited mica insulation. Again the insulation over the full length of connection 20 is continuous and crack-free because coating 24 bridges over the interface region between wrapped and bare parts of the series connection and is securely bonded to both. In this instance the overlap is appro~imately lO0 mils which is the thickness of coating 24 on the unwrapped or bare part of the element.
Coil formette 30 of Fig. 3 comprises four coils 31, 32, 33 and 34 and three series connections 35, 36 and 37. As in the case of series connection 20 of Fig. 2, these three are wrapped to some extent with the mica tape insulation which covers the four coils. The junctions of connections 35, 36 and 37 are not wrapped at the stage of assembly illustrated in this view.
Completion of the insulation system of the assembly of Fig. 3 is again accomplished in accordance with preferred practice of the process of this invention with the result shown in Fig. 4. Thus series connections 35, 3G and 37 of formette 30 are insulated by electrodeposited coatings 40, 41 and 42, respectively. Those coatings, like coating 24 on series connection 20, are each of substantially ~21E3~
uniform thickness about 100 mils and crack-free and c:ontinuous. Further, as a consequence of these coatings being formed as described above by an operation involving dipping of the formette in an electrodeposition bath of the kind specified herein, the ends of each coating have the geometry of coating 13 ofFig. 1, overlying the mica tape insulation and bridging across the interface between the taped and untaped parts of the series connection.
The dipping operation just mentioned is illustrated in Fig. 5 in which an electric motor stator 50 is suspended in coating vessel 52 with series connections 54 of the motor coils immersed in electrocoating solution bath 56. The dapth of this immersion is sufficient to insure that the tape insulation on the series connections is submerged to at least the extent that overlap of electrodeposited insulation is desired, then D.C. potential is applied to the system with vessel 52 serving as the ground and the power source suitably being a D.C. generator.
The compositional range of the electro-deposition bath in accord with the invention in weight percent is summarized below:
Component Broad Ranqe Preferred Ran~e Mica 5 - 35% 10 - 15%
Soluble Resin Binder 0.2 -2% 0.5 - 1.5 (as solids) Electrolyte 0.001 - 0.20% 0.002 - 0.05%
Nonionic Surfactant 0 - 0.3% 0.03 - 0.10%
30 Water Balance Balance The electrical connection or group of ~ ,. ~
: "
8~72~
17M~ 3181 connections to be insulated are coated by electrodeposition. The connection is immersed in the aforementioned bath. A direct current (D.C.) potential is applied to the conductor in the connection, typically in the range of ~20 to ~150 volts. Simultaneously, a grounded counterelectrode must be present in the bath. The mica flakelets in suspension are attracted to the anodic connection and are deposited there as long as current flows from it.
The organic binder also codeposits with the mica flakes. Typical deposition times range from 20 to 500 seconds, depending on the binder, electrolyte concentrations and the thickness of the insulation coating desired.
The interface betwe~n the electrodeposited mica and the taped insulation is the region of greatest difficulty in achieving a consolidated, crack-free insulation, due to the properties of the two dissimilar insulation materials. In some instances depending on the type of mica tape used, better adhesion, between the electrodeposited mica and the tape, can be accomplished when a nonionic surfactant, i.e., one that does not undergo migration in an electric field, is incorporated into the deposition bath. A typical nonionic surfactant is Tergitol NPX (alkyl phenyl e~her of polypropylene glycol), available from Union Carbide Corporation.
When enough mica has been deposited, the D.C. current is switched off and the connection is removed fro~ the bath. The initial wet coating on the connection is a composite of mica flakelets, binder solids and water. This coating is allowed to dry at a temperature greater than 0C and less than 100C, but preferably from about 25C to about 75C. l'he residual water is baked out in an oven at an elevated temperature. At the same time the elevated ... - .,. . ~, temperature serves to cure the binder~ The result is a dry, micaceous coating which is porous and contains enough binder to hold the mica flakes together.
The next step is a post-impregnation treatment of the porous coating, in which the connection is either dipped into an impregnating varnish or, more preferably, treated by vacuum-pressure impregnation with a suitable epoxy or polyester resin. This impregnation treatment can, in many instances, be part of the same cycle whereby other conventional insulations in the dynamoelectric machine are also being resin treated~ Frequently in the actual dynamoelectric machine there are two such post impregnation treatments.
The final step consists of an elevated temperature bake to cure the impregnated resin.
Generally, the curing step includes heating to a temperature of 150 to 180C for a time of four to si~
hours. Longer curing times can be used, but are usually not necessary. ~he higher the temperature the shorter the time required for a satisfactory cure. A
typical curing step is at a temperature of 160C for a time of six hours.
The resulting prvduct is a micaceous connection insulation, consolidated and void-free.
This procedure has the advantages of using low-cost mica and elminating all taping operations in the connection region. In instance~ in which a wire or coil terminal is to be connected to a wire or coil and then used as a connector, it may be kaped over initially with a suitable tape and after the plating process is complete the underlying tape and the insulation deposited thereover may be removed.
The invention is further described by the following examples in which all mesh is given in U.S.
Standard sieve siæes and all percentayes are given in 17~Y
weight percent.
Example I
A representative model of a conventional high-voltage motor coil connection was made by overlapping two rectangular copper strips about 1/2"
and brazing them together. This joined connection was then bent in the shape of a "U", and insulated with conventional mica tapes on the ends only. To insulate ths bare copper portion, the connection model was immersed in a metal vessel containing a bath of the following composition: 900 grams of 325 mesh wet ground muscovite mica powder; 170 grams o~ a water soluble polyester resin varnish, available as Sterling WS-200 WAT-A-VAR, from Reichold Chemicals, Inc.; 2 grams of ammonium nitrate electrolyte, and enouyh distilled water to bring the volume up to 2 gallons.
The model was immersed in the bath for a period of 2 minutes to eliminate air from the submerged taped insulation portion. Using a metal vessel as the ground, an anodic potential of 60 volts D.C. was applied for 350 seconds to deposit the mica and binder. Thereafter the model was dried for 15 hours at 25C and baked 6 hours at 160C. It was subsequently vacuum-pressure impregnated with an accelerated version of an epoxy resin consisting in weight percent of about a 60~-~y ~ and 40%
a liquid Bisphenol A-diglycidyl ether epoxy, as disclosed in Markovitz United States Patent Number 3,812,214 which issued May 21, 1974.
Thereafter, the epoxy was cured 6 hours at 160~C.
The result was the deposition of a smooth, uniform inuslation/ about 125 mils thick, coating the bare portion, and two overlapping portions that rise over the conventionally taped insulation by about 120 mils. The mica content of the coating was determined to be 36.9~. The two overlapping portions between the electrodeposited and conventional insulation werc wrapped with a 2" metal foil, and when subjected to electrical testing, it was found that over 35,000 volts at 60 Hz were applied, between the copper strips and foils, without failure of the insulation.
Example II
A high-voltage connection model was prepared from a rectangular copper strip by insulating half of its length with conventional mica tape. The following bath was prepared for coating the bare copper portion of this strip: 7,500 grams of 325 mesh wet ground muscovite mica powder; 900 grams of a water soluble polyester varnish, available as Aquanel 513 from Schenectady Chemicals, Inc~; 17 grams of basic aluminum acetate (stabilized with boric acid); 7 grams of ammonium nitrate, and enough distilled water to bring the volume up to 32 liters.
The model was immersed for several minutes to eliminate air from the taped insulation, and then an anodic potential of 60 volts D.C. was applied for 105 seconds. The model was then removed and dried at 25C overnight, and baked 6 hours at 160C. It was subsequntly vacuum-pressure :impregnated with an epoxy resin as described in Example I, and cured for 6 houxs at 160~C.
The result was a uniform void-free micaceous insulation about 200 mils thick, and overlapping the upper portion of the mica tape insulation by about 200 mils. A metal foil was wrapped over the interface, and electrical failure did not occur until a potential of 40,000 volts at 60 Hz was reached.
Example III
A connection model for a large generator was prepared by soldering together 3 lenths of 1-1/8" oOd.
copper tubing in the shape of a "T".
A bath for coating this object was prepared ~2~
as follows: 5,600 grams of 325 mesh wet ground muscovite powder; 560 grams of Aquanel 513 soluble polyester varnish; 17,5 grams o~ basic aluminum acetate (stabilizPd with boric acid), and enough distilled water to bring the volume up to 34 liters.
The "T" shaped object was then immersed in this bath, and an anodic potential of 60 volts D.C.
was applied for a period of 300 seconds. I'hereater, the object was removed and allowed to dry at 25C
for 24 hours. It was then baked 6 hours at 160C, and subsequently impregnated with the epoxy resin, as and according to the procedure described in Example I.
The final cure was for 6 hours at 16QC.
This process resulted in a uniform micaceous insulation on the outside surface of the copper tubing which was about 75 mils thick and contained about 35 mica. When the region about the corners of the "T"
were wrapped with metal foil, voltage was applied up to 25,000 volts without failure.
Example IV
A multiple coil motor model, known as a formette, was constructed using 4 motor coils placed in a fixture similar to the stator of a high-voltage motor. These coils were insulated with conventional mica tapes and wrappers, except for the leads, which consisted of bundles of six bare rectangular copper wirer The leads were joined in series from one coil to the next by brazing, resulting in 3 bare seri~s connections. A bath for electrodeposition of mica onto these leads was prepared by mixing the following constituents: 1,800 grams of 325 mesh wet ground muscovite powder; 3~0 grams of Sterling WS-200 WAT-A-VAR water soluble polyester varnish; 4 grams ammonium nitrate electrolyte, and enough distilled water to bring the volume up to ~ gallons.
The end region of the formette was immersad ~ ~8~
in the bath so that all of the bare copper connections were submerged. An anodic potential of 70 volts D.C.
was applied for 270 seconds. Thereafter the formette was removed, dried at 25C for 24 hours, and then baked for 6 hours at 160C. Following this, the electrodeposited insulation along with the conventional taped insulation was impregnated with an epoxy resi~ as disclosed in Example I. I~e resin was then cured for 6 hours at 160C.
The result was a continuous insulation around the coil connections about 110 mils thick and overlapping the taped insulation by about 100 mils.
Example V
Three high-voltage motor connection models were prepared by bending 15" copper strips in the shape of a "U", and insulating the ends with mica tapes, similar to the method described in Example I.
A coating formulation was prepared in a metal vessel by mixing the following consituents: 900 grams of 325 mesh wet ground muscovite mica powder; 170 grams of Aquanel 550 water soluble polyester varnish; 2 grams of ammonium nitrate; 4 grams of Tergitol NPX nonionic surfactant available from Union Carbide Corporation, and enough distilled water to bring the total volume up to 2 gallons.
The bare copper portion of each model was coated by immersing the model in the bath and applying an anodic potential of 60 volts D.C. for a period of 180 seconds. Thereafter, the objects were allowed to dry overnight at 25C, and then baked 6 hours at 160C. Following this, they were vacuum-pressure impregnated with an epoxy resin as described in Example I, and cured 6 hours at 160C.
The foregoing resulted in a smooth uniform micaceous insulation about 120 mils thick and overlapping the taped insulation by about 130 mils.
... .... .
8~7~
The insulation integrity was tested by applying 9000 volts at 60 Hz between the outside surface and the copper, and found to pass without failureO
Thereaftsr, the models were thermally cycled by repeatedly passing current through the copper to heat it to 190C, and subsequently permitted to cool in air to 30C. After 2000 such cycles, the models were tested by immersion in water containing a wetting agent for 30 minutes. The 4600 volts at 60 Hz were applied to the submerged samples without any dielectric failure occurring.
Example VI
Three high-voltage motor connection models were prepared as described in Example V. A coating formulation was prepared by mixing the following constituents in a metal vessel: 900 grams of 325 mesh wet ground muscovite mica powder; 170 grams of Aquanol 513 water soluble polyester varnish; 2 grams of ammonium nitrate; 4 grams of Tergitol NPX nonionic surfactant; and enough distilled water to bring the total volume up to 2 gallons.
The bare copper and insula~ed portions of each model were coated by immersing the model in the bath, and applying an anodic potential of 60 volts D.C. for a period of 140 seconds. Thereafter, the objects were allowed to dry overnight at 25C and then baked 6 hours at 160C. Eollowing this they were vacuum-pressure impregnated with an epoxy resin as described in Example I, and cured 6 hours at 160C.
This resulted in a smooth uniform micaceous insulation about 130 mils thick, and overlapping the taped insulation by about 130 mils. The insulation was tested by applying 9000 volts at 60 Hz as in Example V, without failure. These models were 35 thermally cycled from 190C to 30C for 2000 times as in Example V and tested at 4600 volts at 60 Hz under ., : . . :
~ . .
:
17M~ 3181 water after 30 minutes submersion, without ~ailure~
One model was then placed back on the thermal cycling test for an additional 3136 cycles, removed, and submerged under water. It passed the 4600 volt test.
ExamE~le VII
A formulation of the coating composition of the present invention was prepared by mixing the following ingredients; 5,600 grams of 88 mesh muscovite mica powder available from franklin Minerals, Inc., 560 grams Aquanel 513 water soluble insulating varnish available from Schenectady Chemicals, Inc. (28% solids of an oil modified polyester), 2.5 grams sodium chloride, and enough distilled water to bring the bath volume up to 34 liters.
A rectangular copper wire, .162" x .322"
cross section, was immersed in the coating formulation coaxial with respect to a 3 inch copper tube at ground potential. Mica and binder were electrodeposited on the wire by applying an anodic potential of 60 volts D~Co for 80 seconds. The coated wire was removed from the bath and dried at 25C for 15 hours, and the binder cured at 165C for 4 hours, resulting in a porous micaceous coating.
Thereafter, the coating was vacuum/pressure impregnated with an epoxy resin consisting of 60~
cycloaliphatic and 40% Bisphenol A epoxy, as disclosed in Markovitz, U.SO Patent 3,812,214. The epoxy was cured for 6 hours at 160C to yield a consolidated, 30 void-free insulation 30 mils thick containing 40.4%
mica. The insulation was voltage endurance tested by wrapping the insulated wire spirally with a 40 mil bare Cu wire and applying 7,500 volts at 60 Hz. m e insulation survived the corona and voltage stress for 5,035 hours.
17MY 31~1 Example VIII
Following the procedure of Example VII, a formulation was prepared consisting of 900 grams of 325 mesh muscovite powder, 200 grams of Aquanel 513 water soluble polyester varnish, 2 grams of ammonium nitrate, diluted to 2 gallons with distilled water and stored in a tin coated steel container.
A test sample was prepared from two parallel copper bars, having rectangular cross sections of 1 inch x 1/4 inch, and 6 inches in legnth. The bars were separated ~y two 3/8 inch thick phenolic spacers placed at either end of the bars and the bars were bolted together. The sample was then immersed in the coating formulation. Mica and binder were deposited thereon by applying an anodic potential of 100 volts D.C. for a time of. 400 seconds. The metal container was grounded and became the cathode of the electrical deposition system. The bars were removed and dried 15 hours at 25C, then 6 hours at 105C, and finally 6 hours at 160~F. Thereafterr the bars were vacuum/pressure impregnated with an accelerated version of the epoxy resin disclosed in Example I, and the resin cured at 160C for 6 hours. The resulting insulation measured 130-137 mils thick on the outside faces of the hars and 102-107 mils on the inner faces. This represents a reduction in insulation thickness of only about 15% in the electrically shielded region.
This example demonstrates how an improved uniformity of insulation build can be achieved in regions where electrical shielding or enhancement occurs simply by adjusting the concentration of water soluble binder.
As a comparison, the same copper bar configuration immersed in a bath containing the same constituents as in Example IV and 100 grams of .
.. . .. .
~.,, . .
.
:.
7~
T~ - 20 -Aquanel 513 instead of 200 grams results in insulation builds of 252 mils and 85 mils on the outer and inner aces, respectively. Here, a reduction in thickness of ~G% occurs in the shielded region.
ExamE~le IX
In order to compare the effects of using water soluble resins versus water dispersed resins in the electrodeposition of mica, test samples of two parallel copper bars (designated as bar X and bar Y) were prepared having th~ dimensions and configuration as described in ~xample VIIIo Electrodeposition baths were prepared consisting of 2 pounds of 325 muscovite, 2 grams of ammonium nitrate, 114 grams (on a solid basis) of resin and two gallons of distilled water.
The resin systems compared in the above formulation were as shown in the following table. In the subsequent discussion and tabulation of the experimental results, the electrodeposited samples are identified by the designation of the resin system used.
TABLE II
Resin System A. Water Soluble Resins Al. Aquanel 513, a water soluble polyester, commercially available from Schenectady Chemical Company.
A2. Aquanel 550, a water soluble polyester, commercially available from Schenectady Chemical Company.
T~
A3. GE 111-244, a water soluble polyester/
available from General Electric CompanyO
B. Water Dispersion Resins Bl. Rhople ~ TR-407, an acrylic dispersion resin, commercially available from Rohm and Haas Company.
~x~
B2. Rhoplex AC-1533, an acr~lic dispersion resin, commercially available from Rohm and Haas Company.
B3. Rhoplex AC-1822, an acrylic dispersion resin, commercially available from Rohm and Haas Company.
B4. CavaliteTM, an acrylic dispersion resin, commercially available from E.I. DuPont De Nemours and Company.
Mica and binder were electrodeposited on the wire by applying an anodic potantial of 80 volts D.C. for a time of 180 seconds with the exception that the time in sample B2 was I30 seconds and the sample B4 was 120 seconds.
In all cases the outer coating was thicker than the inside coating, due to an electrical shielding effect. In the case of water soluble resin coatings, improved thickness uniformity between the inside and the outside as indicated by the ratio of I/0 resulted. Water ; dispersion resins, on the other hand were much more in~luenced by the electrical shielding effect as indicated by a significantly lower ratio of I/0.
The results are shown in the following table:
~'"1 , , ''~ ' ,' , , ` ',: ", ,, ", ' :
,' ' ' ,"
' ~.2~
17M~ 3181 TABLE III
Resin System BarsInside Outside Ratio Thick-Thick- I/O
ness~ I ness, O
(mils)(mils) -A. Water Soluble Resins Al. Aquanel 513 X 70 98 .71 Y 7~ 99 .79 A2. Aquanel 550 X 57 98 .58 ~ 60 98 .61 A3. GE lll-244 X 80 102 .78 ~ 88 112 .79 5 B. Water Disper-sion Resin Bl. Rhoplex X 19 49 .39 ~ 19 52 .37 B2. Rhoplex X 42 135 .31 ~C-1533 Y 48 120 .40 B3. Rhoplex X 45 105 .43 Y 54 115 .47 B4. Cavalite X * * *
Y * * *
* Coating did not adhere to test bars and no measurements were possible.
Similar test bars to those used in the thickness test were also prepared, and subjected to a rinse under running water from a Eaucet.
Sample Al, A2 and A3 remained adherent to the bars.
Sample B4 could not be evaluated since it had insufficient adhesion to the bar. Sample B3 washed off easily. Samples Bl and B2 washed ofE partially, leaving exposed portions of copper, and reduced coating thicknesses in other places.
17~ 3181 E~ample X
The utility of water soluble expoxyesters in accoxdance with this invention was tested by prepariny a one gallon aqueous bath of the following ingredients:
l lb of 325 mesh ~ica llO grams Isopoxy 771 (Schenectady Chemicals~
1 gram N~14NO3 Z grams Tergitol NP10 surfactant A coppe~ bar was immersed in thi~ bath at room temperature and maintained at +60 volts for 240 ssconds whereupon the bar was removed, dried 24 hours at 25C and then baked 6 hours at 160C. The bar was then impregnated by vacuum pressure impregnation technique with an epoxy resin and then baked at 160 for 6 hours to cure the epoxy resin. The result was found to be a uniform coating of about 0.210 inch and was void free and of mica content approximating 40 percent. Thus, this coating compared favorably with that produced as described above in Example VII.
Example XI
The suitability of water soluble acrylics was similarly tested in another experiment in which a two gallon aqueous bath was prepared by adding the following to water:
2 lbs of 325 mesh mica 360 grams Acrysol~ S-68 acrylic resin (Rohm & Haas) 4 grams Tergitol NPlO 3urfactant 2 grams Sodium Lauryl sulfate 2 grams Dimethylaminoethanol Again, a copper bar was immersed in this bath and held at ~60 volt~ for 300 seconds whereupon the bar was removed and treated as in Example X with the consequence that a coating of uniform thickness approximating 0.200 inch was produced having a mi~a content of about 40 percent and being void free and comparing again favorably with the insulating coating . .
.
described above in Example VII.
Example XII
A one gallon aqueous bath was prepared by addiny the ollowing to water:
l lb. of 325 mesh mica;
65 grams Carboxy-terminated butadien0/acrylo-nitrile (B.F. Goodrich) 2 grams NH4N03 2 grams Tergitol NPlO
1 gram Sodium Lauryl sulfate This, thus, as a test of the suitability in accordance with this invention of the so called CTBN resins which are described above blended in 65 grams o butyl cellosolve and reacted with 4.6 grams dimethylaminoethanol to render them water soluble. As in Examples X and XI, a copper bar was immersed in this bath and held at 45 volts for 150 seconds then removed and processed as described in Example VIII
with the result that a uniform coating of about 0.12 inch thickness resulted. This insulating coating was found to be void free and to have a mica content approximating 40 percent and to be therefore quite similar to those of Example VII, VIII and IX above.
ExamE~le XIII
To test the suitability of combinations of the~e anionic water soluble resins for the purposes of this invention, a four gallon aqueous bath was prepared by adding Acrysol WS-68 and Aquanel 513 in a ratio to each other about 1.5 to l, the actual formulation being as follows:
480 grams Acrysol WS-68 acrylic resin 340 grams Aquanel 513 polyester rPsin 8 gram~ Tergitol NPID
4 grams Sodium Lauryl Sulfate 8 grams Dimethyl~amino-ethanol 5 grams Ammonium Nitrate and the balance water.
Once again, the copper bar test as described in Example VIII was carried out with successful results in terms of the resulting insulating coating being of uniform thickness approximating 0.21 inch and of mica content approximating 40 percent and being void free and altogether a superior electrical insulating coating of the sort described above in Example VII.
Example XIV
The utility of non-ionic polymer in this invention was tested in an experiment involving the use of l lb. of 325 mesh mica 75 grams of polyethyleneglycol (average mica weight 6,000) 1 gram of ammonium nitrate The mixture was added to one gallon of water and a copper bar test was run as described above in Examples X-XIII. Thus, the copper bar was immersed in this bath and a potential of 60 volts D.C. was applied for about one minute the bar being then removed and found to be completely clean. There was no mica adherence to the bar at all and the polymer was found of itself to be insufficient to hold the mica particles together.
r~
The stability of a cationic polymer was similarly tested in experiments which involved formulation of 1 lb. of 325 mesh mica 2 grams of NH~MO3 80 grams of Poly-2-vinylpyridine dissolved in 80 milliliters of butyl cellosolve 20 grams of acetic acid The mixture was prepared in a volume of one gallon with water and agitated for 30 minutes in a paint shaker to allow the ingredients to disperse and the acid to react with the Poly-2-vinylpyridine to form a ~L2~
17MY 31~1 polyelectrolyte. Then two copper strips were immersed in the bath spaced about two inches apart, the potential of 60 volts D.C. was applied to the strips.
Immediately mica was observed to begin accumulating about the anode while at the cathode a gelatinous accumulation was observed. After 60 seconds, the voltage was dropped to zero and the strips were removed. The mica deposit at the anode having no binder slipped off the wire and could not be removed from the bath, thus demonstrating the generic inability o~ cathodic deposition resins to bind or hold material deposited at the anode.
The data obtained from these tests substantiate the fact that in electrodeposition of mica improved results can be obtained using anionic water soluble resins as compared to water dispersion resins and to non-ionic and cationic water soluble resins.
In this specification and in the appended claims wherever percentage or proportion are stated, reference is to the weight basis unless otherwise specifically noted.
It will be appreciated that the invention is not limited to the specific details shown in the illustrations, and that various modif:ications may be rnade within the ordinary skill in the art without departing from the spirit and scope of the invention.
Claims (14)
1. A process for depositing an insulating coating on bare portions of electrical connection members comprising the steps of:
(a) immersing the bare electrical connections in an aqueous electrodeposition composition consisting essentially in weight percent of 5-35% of particulated mica, 0.2-2% of a water soluble anionic resin binder as calculated in resin solids, 0.001-0.20% of an electrolyte, up to 0.3% of a nonionic surfactant and a polar solvent making up the remaining weight percent, (b) electrodepositing said composition on the bare electrical connections and forming a dry micaceous coating of substantially uniform thickness, said coating being porous and containing a sufficient amount of binder to hold the mica particles together;
(c) impregnating the porous coating with an impregnative resin varnish; and (d) subjecting the impregnated coating to an elevated temperature bake to cure the resin varnish.
(a) immersing the bare electrical connections in an aqueous electrodeposition composition consisting essentially in weight percent of 5-35% of particulated mica, 0.2-2% of a water soluble anionic resin binder as calculated in resin solids, 0.001-0.20% of an electrolyte, up to 0.3% of a nonionic surfactant and a polar solvent making up the remaining weight percent, (b) electrodepositing said composition on the bare electrical connections and forming a dry micaceous coating of substantially uniform thickness, said coating being porous and containing a sufficient amount of binder to hold the mica particles together;
(c) impregnating the porous coating with an impregnative resin varnish; and (d) subjecting the impregnated coating to an elevated temperature bake to cure the resin varnish.
2. The process of claim 1, wherein the said composition is electrodeposited on the bare electrical connection members at an anodic potential of 20 to 150 volts D.C. for a time of 20 to 500 seconds.
3. The process of claim 2 wherein a portion of said members adjacent said bare portions are covered by electrical insulation.
4. The process of claim 3 wherein said deposited micaceous coating covers the electrically insulated portions adjacent the bare portions of said connection members to provide continuously insulated members.
5. The process of claim 2, wherein the resin varnish is a member selected from the group consisting of epoxy resin and polyester resin and the elevated temperature bake is at a sufficient temperature and for a sufficient time to form a consolidated and void-free micaceous connection insulation.
6. The process of claim 1, wherein an elevated temperature of about 150°C to 180°C is maintained for a time of about 4 to 6 hours.
7. The process of claim 5, wherein said bare electrical connections join stator coils in dynamoelectric machines and wherein, prior to said immersing, portions of said stator coils adjacent to said connections have been covered with insulating micaceous tape.
8. The process of claim 7, wherein said stator coils are immersed in the aqueous electro- deposition composition and said composition is electrodeposited on said bare electrical connections to form a coating thereon that overlaps the insulating micaceous tape.
9. The process of claim 5, wherein the impregnating step is performed under conditions including the use of vacuum and pressure.
10. The process for providing a continuous insulating covering on an electrical conductor which comprises the steps of:
(a) wrapping a portion of the length of the conductor with insulating material;
(b) then immersing a bare unwrapped portion of the conductor and the adjacent wrapped portion thereof in an aqueous electrodeposition composition consisting 5-35%
of particulated mica, 0.2-2% of a water soluble anionic resin binder as calculated in resin solids, 0.001-0.20% of an electrolyte, up to 0.3% of a nonionic surfactant and a polar solvent making up the remaining weight percent;
(c) electrodepositing said composition on the bare unwrapped portion of the conductor and the adjacent wrapped portion and forming a continuous dry micaceous coating on the bare unwrapped and adjacent wrapped portions, said coating being porous and containing a sufficient amount of binder to hold mica particles together;
(d) impregnating the porous coating with an impregnative resin varnish; and, (e) subjecting the impregnated coating to an elevated temperature bake to cure the resin varnish.
(a) wrapping a portion of the length of the conductor with insulating material;
(b) then immersing a bare unwrapped portion of the conductor and the adjacent wrapped portion thereof in an aqueous electrodeposition composition consisting 5-35%
of particulated mica, 0.2-2% of a water soluble anionic resin binder as calculated in resin solids, 0.001-0.20% of an electrolyte, up to 0.3% of a nonionic surfactant and a polar solvent making up the remaining weight percent;
(c) electrodepositing said composition on the bare unwrapped portion of the conductor and the adjacent wrapped portion and forming a continuous dry micaceous coating on the bare unwrapped and adjacent wrapped portions, said coating being porous and containing a sufficient amount of binder to hold mica particles together;
(d) impregnating the porous coating with an impregnative resin varnish; and, (e) subjecting the impregnated coating to an elevated temperature bake to cure the resin varnish.
11. The process of claim 10 including the steps of baking the electrodeposited coatings and thereby removing substantially all the moisture therefrom and curing the resin binder prior to impregnating the porous coating with an impregnative resin varnish.
12. In the process for insulating a multiple coil stator of a dynamoelectric machine which includes the steps of wrapping the coils and portions of the coil leads with insulating tape and joining the coils in series by securing the respective coil leads together in pairs as coil connections, the combination of the steps of immersing the stator in an aqueous electrodeposition bath so that bare unwrapped portions and adjacent insulation-covered portions of the coil leads are submerged in the bath, and applying an anodic potential and thereby electrodepositing on both the bare portions and the adjacent wrapped portions of the coil leads a coating of substantially uniform thickness greater than about 50 mils, said aqueous bath consisting essentially of 5-35% of particulated mica, 0.2-2% of a water soluble polyester resin binder as calculate din resin solids, 0.001-0.20% of an electrolyte, up to 0.3% of a nonionic surfactant and the remainder water.
13. In an electric motor assembly including a plurality of insulated coils connected in series by brazing, the combination of electrodeposited insulation covering the brazed free ends of the coil leads and overlapping coil insulation adjacent thereto. the electrodeposited insulation in each instance having been electrodeposited from an aqueous bath consisting of 5-35%
of particulated mica, 0.2-2% of a water soluble polyester resin binder as calculated in resin solids, 0.001-0.20% of an electrolyte, up to 0.3% of a nonionic surfactant and the remainder water, the electrodeposited insulation being in contact with both the coil lead insulation and coil lead exposed metal surface and being continuous and crack free and of substantially uniform thickness greater than about 50 mils on the brazed ends of the leads but tapering in thickness on the coil insulation.
of particulated mica, 0.2-2% of a water soluble polyester resin binder as calculated in resin solids, 0.001-0.20% of an electrolyte, up to 0.3% of a nonionic surfactant and the remainder water, the electrodeposited insulation being in contact with both the coil lead insulation and coil lead exposed metal surface and being continuous and crack free and of substantially uniform thickness greater than about 50 mils on the brazed ends of the leads but tapering in thickness on the coil insulation.
14. The assembly of claim 13 in which the electrodeposited coating on the brazed ends of the coil leads is about 120 mils in thickness and extends about 130 mils in length over the coil insulation.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/702,525 US4615778A (en) | 1983-11-25 | 1985-02-19 | Process for electrodepositing mica on coil or bar connections and resulting products |
| US702,525 | 1985-02-19 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1288726C true CA1288726C (en) | 1991-09-10 |
Family
ID=24821562
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000493348A Expired - Fee Related CA1288726C (en) | 1985-02-19 | 1985-10-18 | Process for electrodepositing mica on coil or bar connections and resulting products |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1288726C (en) |
-
1985
- 1985-10-18 CA CA000493348A patent/CA1288726C/en not_active Expired - Fee Related
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