CA1084573A - Lamination of stator core punchings - Google Patents
Lamination of stator core punchingsInfo
- Publication number
- CA1084573A CA1084573A CA284,191A CA284191A CA1084573A CA 1084573 A CA1084573 A CA 1084573A CA 284191 A CA284191 A CA 284191A CA 1084573 A CA1084573 A CA 1084573A
- Authority
- CA
- Canada
- Prior art keywords
- segments
- stator core
- filler
- coating
- core
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K15/00—Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines
- H02K15/02—Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines of stator or rotor bodies
- H02K15/024—Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines of stator or rotor bodies with slots
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K1/00—Details of the magnetic circuit
- H02K1/04—Details of the magnetic circuit characterised by the material used for insulating the magnetic circuit or parts thereof
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Insulation, Fastening Of Motor, Generator Windings (AREA)
- Manufacture Of Motors, Generators (AREA)
- Iron Core Of Rotating Electric Machines (AREA)
Abstract
LAMINATION OF STATOR CORE PUNCHINGS
Abstract of the Disclosure Lamination of the stator core is accomplished by stacking the core with a series of segments or punchings of steel each of which is insulated with a layer of adhesive enamel on both sides.
The adhesive enamel is comprised of an epoxy resin and a sufficient amount of a glass fiber spacer filler to substantially provide uniform separation and insulation between the individual segments.
Abstract of the Disclosure Lamination of the stator core is accomplished by stacking the core with a series of segments or punchings of steel each of which is insulated with a layer of adhesive enamel on both sides.
The adhesive enamel is comprised of an epoxy resin and a sufficient amount of a glass fiber spacer filler to substantially provide uniform separation and insulation between the individual segments.
Description
` .' `. !
89~573 1 7GE-2 ~54 LAMINATION OF STATOR CORE PUNCHINGS
Large turbine driven generators are used in the production of electrical power. The two major parts of a generator are known by electrical designation as the field and the armature. A field eonsists of a source of magnetic lines of flux, which is made from a wound eoil that becomes an eleetromagnet. Since the part rotates lt ls ealled the "rotor". The armature is an assembly of eonduetors in which voltage is lnduced. It has been ealled the "statorn, beeause lt is the stationary part of the equipment. A
detailed deseription of such machines is given in a publication by Y. S. Hargett, Large Steam Turbine-Driven Generators, General Electric Co., Scheneetady, N. Y., August 1967.
The stator includes the stator core, the stator frame and the stator windings. The function of the stator eore is to provide a low reluetanee path for the llnes of magnetie flux from the field, and at the same time to support the eoils of the stator winding. The stator frame supports the stator eore within the generator. The armature winding is formed by insulated bars or half eoils assembled ln stator eore slots and ~oined at the ends to form coils and eonneeted in the proper phase belts by eonneetion rings at the end of the
89~573 1 7GE-2 ~54 LAMINATION OF STATOR CORE PUNCHINGS
Large turbine driven generators are used in the production of electrical power. The two major parts of a generator are known by electrical designation as the field and the armature. A field eonsists of a source of magnetic lines of flux, which is made from a wound eoil that becomes an eleetromagnet. Since the part rotates lt ls ealled the "rotor". The armature is an assembly of eonduetors in which voltage is lnduced. It has been ealled the "statorn, beeause lt is the stationary part of the equipment. A
detailed deseription of such machines is given in a publication by Y. S. Hargett, Large Steam Turbine-Driven Generators, General Electric Co., Scheneetady, N. Y., August 1967.
The stator includes the stator core, the stator frame and the stator windings. The function of the stator eore is to provide a low reluetanee path for the llnes of magnetie flux from the field, and at the same time to support the eoils of the stator winding. The stator frame supports the stator eore within the generator. The armature winding is formed by insulated bars or half eoils assembled ln stator eore slots and ~oined at the ends to form coils and eonneeted in the proper phase belts by eonneetion rings at the end of the
2 0 windings .
The stator core is made in the form of a cylinder of high permeability steel which fully encloses the eircumference of the field. 1'he stator core is of a laminate construction .-~ 573 wherein the construction may be accomplished by stacking the core -with a series of overlapping segments or punchings of steel, each of which ls insulated with a layer of enamel on both sides. In one arrangement these segments are stacked on key bars at the outside diameter which maintain the alignment of the outer edges. The complete core for a large generator may c~ntain several hundred thousand individual segments or punchings.
; The core has been assembled in the past by workmen depositing the laminations by hand. Altematively, the laminations may be stacked mechanically by an apparatus disclosed by J. G.
Qulnn, U. S. patent 2,889,058 entitled, Lamination Stacking Machine. Heretofore, the laminations were then coated with an enamel for electrical insulation from abutting laminations. It ls essential that the individual laminations in the stator core remain separated and lnsulated from each other to prevent circulating current between laminations.
The stator laminations are pressed at intervals during the stacking process to flatten them and achieve compact assembly.
When fully stacked, the entire core has heretofore been clamped end-to-end with pressure and held by nuts on the full length of the key bars. The end-to-end clamping pressure produces friction between the individual laminations to make the complete core behave almost like a solid cylinder. Although the stator core is very stiff, deflection takes place due to the magnetic power of the field. This results in vibrations which must be suppressed within the machine.
- .
' ~0~5'~3 17GE-2~54 In order to prevent vibration, an additional adhesive is applled to certairl areas of the stator core, i.e., about 5% of the core at the end irons, to impart rigidity to the structure. It is not practical or economical to apply two coatings, i.e., an insulating coating and an adhesive coating, to all the laminations since this requires passing each of the up to several hundred thousand per machine laminations through the coating apparatus twice. Howe~ter, previous ~ -`
attempts to eliminate the dual step process of cured insulating enamel plus adhesive bond in favor of a single coating functioning both as adhesive and lnsulation have not been completely satisfactory due to surface irregularities of the punchings.
Quite surprisingly, we have discovered that we can sub-stantially laminate the entire core by means of a chemical bond and using a single adhesive-insulating coating applied to the punchings.
Advantages provided by our novel system include the formation of an lntegrally bonded stator core by means of a single adhesive insulating coating, lmprovement of heat transfer between lamlnatlons, and curing and bonding the stator core by a sin~le step. It now becomes feasible to form the stator frame and such prebonded modules be assembled outside of the stator frame and such prebonded modules can be tested prior to being placed in the generator.
In accordance with the invention, we have discovered a method of laminating a stator core by stacking a series of segments or punchings of steel each of which is coated with a sing!e layer of 25 ~ adhesive insulating enamel on both sides. The enamel is comprised of an epoxy resin and a sufficient amount of a glass fiber spacer filler to substantially provide a uniform separation and insulation
The stator core is made in the form of a cylinder of high permeability steel which fully encloses the eircumference of the field. 1'he stator core is of a laminate construction .-~ 573 wherein the construction may be accomplished by stacking the core -with a series of overlapping segments or punchings of steel, each of which ls insulated with a layer of enamel on both sides. In one arrangement these segments are stacked on key bars at the outside diameter which maintain the alignment of the outer edges. The complete core for a large generator may c~ntain several hundred thousand individual segments or punchings.
; The core has been assembled in the past by workmen depositing the laminations by hand. Altematively, the laminations may be stacked mechanically by an apparatus disclosed by J. G.
Qulnn, U. S. patent 2,889,058 entitled, Lamination Stacking Machine. Heretofore, the laminations were then coated with an enamel for electrical insulation from abutting laminations. It ls essential that the individual laminations in the stator core remain separated and lnsulated from each other to prevent circulating current between laminations.
The stator laminations are pressed at intervals during the stacking process to flatten them and achieve compact assembly.
When fully stacked, the entire core has heretofore been clamped end-to-end with pressure and held by nuts on the full length of the key bars. The end-to-end clamping pressure produces friction between the individual laminations to make the complete core behave almost like a solid cylinder. Although the stator core is very stiff, deflection takes place due to the magnetic power of the field. This results in vibrations which must be suppressed within the machine.
- .
' ~0~5'~3 17GE-2~54 In order to prevent vibration, an additional adhesive is applled to certairl areas of the stator core, i.e., about 5% of the core at the end irons, to impart rigidity to the structure. It is not practical or economical to apply two coatings, i.e., an insulating coating and an adhesive coating, to all the laminations since this requires passing each of the up to several hundred thousand per machine laminations through the coating apparatus twice. Howe~ter, previous ~ -`
attempts to eliminate the dual step process of cured insulating enamel plus adhesive bond in favor of a single coating functioning both as adhesive and lnsulation have not been completely satisfactory due to surface irregularities of the punchings.
Quite surprisingly, we have discovered that we can sub-stantially laminate the entire core by means of a chemical bond and using a single adhesive-insulating coating applied to the punchings.
Advantages provided by our novel system include the formation of an lntegrally bonded stator core by means of a single adhesive insulating coating, lmprovement of heat transfer between lamlnatlons, and curing and bonding the stator core by a sin~le step. It now becomes feasible to form the stator frame and such prebonded modules be assembled outside of the stator frame and such prebonded modules can be tested prior to being placed in the generator.
In accordance with the invention, we have discovered a method of laminating a stator core by stacking a series of segments or punchings of steel each of which is coated with a sing!e layer of 25 ~ adhesive insulating enamel on both sides. The enamel is comprised of an epoxy resin and a sufficient amount of a glass fiber spacer filler to substantially provide a uniform separation and insulation
-3-, ~ ~Q~ 3 17GE~2454 between the individual segments. The laminated core is integrally bonded by means of an adhesive chem~cal bond. In one aspect of the invention, we have discovered a method of forming a bonded stator core by the steps of forming steel segments having an inorganic S coating thereon, applying an insulating adhesive coating on both sides of the segments, the coating comprising an epoxy resin, a '~
curing agent for the resin which provides latency at room temperature and coupled with a cure at elevated temperatures, a glass fiber spacer filler having a diameter of about 0.45-0.55 mil ln an amount sufflcient to provide uniform separation and insulation between the segments, lnorganic fillers to provide a working viscosity and maintain the glass fiber homogeneously dispersed in the resin, and a suitable solvent for application of the coating. Thereafter the solvent is removed from the coated segments, the dried and tack-free coated segments are stacked in a configuration of an element for forming a substantlal portion of or the entire stator core and the element is pressed and cured under condltlons of temperature and pressure to form an lntegral bond between the segments. Another aspect of our invention relates to an lntegrally bonded stator core for a generator comprislng a series of secJments of steel each of which is bonded to and insulated from an adjacent segr:lent, and an interlayer between the segments for bonding and insulatiny the segments, the interlayer being a thermally cured epoxy resin and a glass fiber filler having a uniform diameter of about 0.45-0.55 mll to provlde uniiorm separation and insulation between the segments.
The laminations or segments are approximately 0.010 to 0.030 inch thick and are stamped from a suitable grade of magnetic - ~ - _ . . .. . .. .. .
, "
:
"`` lO~S'~3 steel strip stock and then appropriately heat treated and coated with a thin inorganic coating, e.g., 0.10-0.25 mil coating of magnesium phosphate to keep the laminations separated prior to use. This coating has been designated as C-10 by the steel manufacturer. The segments are like a series of flat cards which are pie-shaped so that they may be stacked on key bars at the outside diameter and the inside diameter has slots in which the stator winding is later assembled as shown in Figure 3 of the J. G. Quinn patent cited hereinabove. While the surfaces of a segment appear normally smooth and regular, under magnifi-cation the surfaces are really quite irregular and there appear to be elevations or peaks and depressions or valleys. Attempts to form laminations using a single coating of an ordinary bonding composition between the segments having a critical thickness of about 0.5 mil are not possible because of the increased probability of laminates becoming shorted together due to the surface irregularities.
Reference will be made hereinafter to the accompanying drawings, in which:
Figure 1 is a schematic sectional view of a generator, Figure 2 is a view of a group of bonded laminations, Figure 3 is an enlarged sectional view taken through several laminations, showing the coating according to the invention, and Figure 4 is an enlarged portion of Figure 2, referred to as "Surface Section A".
As we have mentioned above the stator core of a large dynamoelectric generator may contain as many as several hundred thousand segments. The coating on the top and on the bottom of each segment of such an enormous machine has been critically defined as about 0.45-0.55 mil. The generating equipment is designed and built for high reliability and long life. Thus, factorsSuch as the interlayer between laminations must be extremely precise. Since the inorganic coating on each side of a segment is about 0.10 mil, the remainder or about 0.35-0.45 mil is the thickness of the insulating adhesive.
The insulating adhesive comprises about the following composition:
--`-- 1084573 Inqredient Broad Ran~e (wt.%) Preferred (wt.%) Epoxy resin 30-35% 30.4-31%
Curing agent up to 4% 1.6-2.3%
Accelerator up to 1% about .8%
Glass fiber spacer 10-25% 10.3-20%
Inorganic filler 10-25% 16.1-21.8%
Organic solvent 25-40% 30.5-35.2%
Any of the conventional epoxy resins having 1, 2-epoxy groups are useful in connection with the present invention. These resins are commercially available and have the general formula:
O O
/ \ /\
I. CHz-CH-Y-CH-CH2 wherein Y is the residue of the reaction product of a polyfunctional halohydrin, such as epichlorohydrin, and a polyhydric phenol. These reslns are well known and commerclally available. Typlcal phenols useful ln the preparatlon of the resin are resorcinol and various bisphenols resultlng from the condensatlon of phenol with aldehydes and ketones such as formaldehyde, acetaldehyde, and acetone.
Representative of the bisphenols is 2,2'-bis(p-hydroxyphenyl)propane (known as Bisphenol A); 4,4'-dihydroxydiphenylsulfone; 4,4'-dihydroxy-2 0 biphenyl; 4, 4 ' -dihydroxydiphenylmethane; 2, 2 ' -dihydroxydiphenyl-oxide, etc.
The epoxy resin useful for most applications in the practice of the present invention corresponds to the general formula:
, II CH2 CH-CH2 O~)R~OCH2 CH-CH1~
I I
LO~)R~OCH~CH-CH2 wherein R is a divalent radical selected frorn the group consisting of saturated alkylene radicals of from 1 to 8 carbon atoms, oxygen, and the sulfone group, y is 0 or an integer having a value up to 25 and n :
is 0 or 1. Specifically, R may be methylene, ethylene, propylene, isopropylene, isopropylidene, butylene, isobutylene, etc.
The most common epoxy resin of this type is the reaction . ~ :
product of epichlorohydrin and Bisphenol A which corresponds to the structural formula:
/H\CH CHfO~C~OCH2CH-CH~L~
CH3 OH I .
--O~)C~OCH / \ "~
wherein y has the meaning given above.
The instant epoxy resins may also be epoxy novolac resins, which are available commercially as CIBA ECN resins. These are derived from an ortho-cresol-formaldehyde novolac which is then reacted with epichlorohydrin to form a polyepoxide. Representative epoxy novolac resins correspond to the formula:
2 2 ~ O CH2 CH CH2 ¦ O CH2 CH CH2 ~CH2~ CH~
wherein y has the value given above.
An epoxy resin which is formed from tetraphenylol ethane and epichlorohydrin is also suitable. An intermediate from which this resln is prepared is illustrated by the formula:
V . -CH2--CH-CH2 0-CH2--CH-CH2 H CH
1 \ ~ /\ ; ' ' ''.' , ,.~,,l The instant epoxy resin may be liquid or solid. It generally has an epoxy equivalent in the range of 100 to 4000 and preferably from 150 to 500. The ep~xy equivalent weight is the weight of resin in grams which contain one gram equivalent of epoxy.
' ,~ ; ' '' ' ''` ., - "" 1084573 ~\ 17GE-24s4 - Curing agents for conventional type epoxy resins are disclosed by S. Oleesky and G. Mohr, Handbook of Reinforced Plastics, Reinhold, New York, pages 74-75. Most of the curing agents described are undesirable for the present application because they promote too rapid cure at room temperature and have a short pot life. The critefia for a desirable curing agent for laminating the large number of segments are that the agent must require elevated temperature for cure and must impart a long pot life. One useful system ls disclosed by M. Markovitz, U. S. patent 3,776,978 which dlscloses a mixture of a phenol and an organic titanate. Also probably useful are those designated as latent curing agents, such as boron trifluoride-monoethylamine complex, triethanolamine borate which have long pot lives and are cure activated by heat; and acid anhy~'.ides, such phthalic anhydride, and mixtures of pyromellitic dianhydrlde and maleic anhydride which require elevated temperature cures .
A preferred curlng agent for the epoxy resins employed herein ls dlcyandiamide having the structure:
NH
Curing can occur through all four nltrogen-containing functional groups. An advantage of dicyandiamide, when used with solid diglycidyl ether of Bisphenol A for laminating applications, is that it ` `
provides latency at room temperature coupled with rapid cures at 145 - 165C. For solid resins, it is normally used in a solvent such as acetone-water, dimethyl formamide or a glycol ether. When ' I; ' '' ' 1 ;; 1' ~ j -~` 1084S73 1 7GE~2 454 thoroughly milled or dissolved into the epoxy system, it will provide a one-container system stable for at least 6 months. While the amount of curing agent can vary to some extent, I have found that an effective amount generally is in the range of about 2.5-7.5 parts by weight per 100 parts of epoxy resin. The preferred concentration of the curing agent for a diglycidyl ether of Bisphenol A resin is about 4 . 7 parts by weight.
Optionally, the adhesive coating composition employing the preferred dicyandiamide curing agent incorporates an imidazole accelerator, especlally a substituted imldazole. These compounds may be represented by the general formula:
R2_ Ic ' R
whereln Rl, R2, and R3 are independently selected from the group conslstlng of hydrogen, lower alkyl, phenyl and lower alkylphenyl.
Particularly useful accelerators in this class are the following compounds:
Imidazole 2 -ethyl-4-methylimidazole l -benzyl-2 -methylimidazole 2 0 l-methylimidazole 1, 2 -methylimidazole ~ r The accelerator in very small amounts serves to decrease ~ -the curing time without a significant sacrifice of shelf life. Thus, 108~S73 -enough of the accelerator should be added to substantially decrease the curing time and not an excessive amount which produces gelation or imparts poor shelf life. An effective amount of imidazole accelerator is about 0.1-0.5 part by weight per 100 parts of epoxy resin, with the preferred amount being about 0.24 part by weight. -- A critical aspect of our invention is the use of fiber spacers which provide a uniformly spaced, positive separation between segments under the conditions of heat and pressure required during curing. The cYlindrical shape of the fibers is highly significant, since once the resin is dried, the fibers must stay locked in place.
In contrast spherical bodies would tend to shift locations during application of heat and pressure. Any of a number of glass ffbers, for example, conventionally available may be used and these include E-glass (silicate glass) and S-glass (magnesium aluminosilicate glass). These glasses can be manufactured to form fibers of great uniformity in diameter whlch provide uniform spacers. The fiber dimensions in addition to uniformlty are very significant: the dlameter should be about 0.50~0.05 mil (12-14 microns) and the length should be about 1/64 to 1/32 inch (400-800 microns). Fiber glass yarn within the prescribed diameter ranges are described by Oleesky and Mohr, previously cited, page 124 as the following:
Product Min . (in . ) Max (in . ) J 0. 00045 0. 00050 K 0 . 00050 0 . 00055 The amount of fiber glass spacers required to l)rovide uniform separation and insulation of the segments is about 10 to 25 percent ` 10~4573 , `' ' , 17GE-2454 by weight of the total adhesive composition. When the amount of fibers is in excess of 25 percent by weight, there is no improvement in separation, but clumping of the fibers occurs together with - tapering. When there are too few fibers, less than about 10 percent by weight, the dielectric strength is penalized with earlier failure and shorts occurring.
The fibers must be uniformly distributed in the adhesive coating sGlution and also on the surfaces of the segments. As a matter of fact deposition across the lamination phase should be so unlform that a monolayer of fibers is obtained without clumping.
Once the fibers are applied they must be relatively fixed in place without sliding on the surfaces of the laminates.
Other lnorganic fillers play an important role in the lnstant coating composition. These fillers are added to stabilize the overall composition, control the viscosity, and maintain the fibers ln suspension. An illustration of such a filler is a hlghly dlspersed slllca avallable commerclally under the trademark Aerosll OX 50 from Degussa Inc., which is produced from silicon tetrachloride ln a flame hydrolysis process with oxygen-hydrogen gas. It has BET
surface area of 50+15 m2/g, an average primary particle size of 40 millimicrons and a bulk density of approximately 80 g/l. Addltional suitable fillers are fumed silica, sold under the name of CAB-O-SIL
(L5) by Cabot Co., and a silica known as MIN-U-SIL sold by Pennsylvania Glass Sand Corp. which has a particle size of about 15 mlcrons. The amount of these other fillers is typically up to about 10 percent by weight and usually in the range of 6-10 percer.t by weight of the total composition.
`` :1084S73 The coating formulation involves a combination of solvents ; and thinners. The uncured epoxy resin is soluble in oxygenatedsolvents, such as ketones, esters and ethers, and in highly halo-genated hydrocarbons. Fast evaporating solutions are based on low boiling ketones such as acetone and methyl ethyl ketone.
The thinners are employed to reduce costs and to regulate viscosity.
I:)etermination of proper solvent balance is somewhat of an art and improper selection will cause difficulties. A proper solvent blend will hold in the curing agent, while providing a continuous fflm.
One typical blend for a diglycidyl ether of Bisphenol A consists of:
Parts Xylene 32 Methylisobutyl ketone 32 B Cellosolve ~ 32 lS Cyclohexanol 4 After the coating has been applied to the segments, the solvent is removed at temperatures up to about 300F for a short residence time of up to about 60 seconds. The dried coatlng is tack-free and remains reactive for bonding for an extended period of time, e.g., four months. Then the coated segments are stacked in a configuration of an eleme ~t for forming a portion or the entire stator core. The element is thereafter pressed and cured at elevated temperatures and pressures. Examples of curing schedules are in a range of about a temperature of 150-170C, a pressure of 200-300 psi and for a period of time of about 1-7 hours. The curing temperature depends to a large extent on the curing agent used to crosslink the ~ ~r2~~ Qr~
~. ' , ' . , .
~084573 17GE-2454 epoxy resin. The optimum curing schedule for a particular agent can readily be determined by routine experimentation by a person skilled in the art.
; Our invention is further illustrated by the following examples:
EXAMPLE I
An adhesive-insulating coating was prepared from the following formulation:
IngredientPart by weight Araldite* 6060 Epoxy resin 31 Dicyandiamide 1.6 2-Ethyl-4-methylimidazolen . 8 (10% solution in cellosolve) Cellosolve* 30.5 MIN-U-SIL 8.1 Aerosil* OX 50 8.0 Glass Fibers (1/64' long, 20.0 0.50 mil dia.) The Araldite* epoxy resin is a diglycidyl ether o~ Bisphenol A.
This composition was dispersed to form a homogeneous enamel for application to the metal segments.
EXAMPLE II
Another adhesive insulating coating was prepared from the following formulation:
*Trade Mark ~ ~084573 17GE-2454 Ingredient Parts by weight Epoxy cresol novolac resin21.1 (ECN 1280) Epoxy novolac resin (DEN 438) 2.3 Tyzor* OG/BRZ-7541(1.1) 2.3 Epoxy resin (Epon 1002) 7.0 Cellosolve* 17.6 n-Butylcellosolve 17.6 Cab-0-Sil fumed silica 10.3 Glass fibers (1/32'long, 10.3 0.50 mil dia.) Min-U-Sil microsilica 11.5 The curing agent Tyzor* OG/BRZ-7541 was tetraoctylglycol ` titanate/phenol formaldehyde novolac containing 2 to 3 phenolic OH groups per molecule. This composition was dispersed to form a homogeneous enamel for application to the metal segments.
EXAMPLE III
Silicon steel punchings manufactured by Allegheny Ludlum Co. and coated with a 0.10 mil coating of magnesium phosphate were then coated with the enamel of Example I to a thickness of about 0.35 to 0.45 mil. The segments were ~; 20 stacked, pressed and cured as shown below. The bond strengths in psi were determined.
(a) A comparison was made to a dual coating system in which the segments were initially coated with an insulating phenolic resin and thereafter coated with an epoxy resin containing no glass fibers. The results as shown in the table below indicate that superior bond strength is obtained by the single bondable coating of our invention.
B
- ~ ~
.
Bond Strength Retention as a Function of Thermal Aging _ 6 0 da ys 15 0 days Initial Aged at Aged at as 180C and 150C and Coating Cure Tested_ tested @ ¦ tested ~_ System Schedule R.T. 130C R.T. 130C R.T. 130C
_ ~Si) ~Sl) ~Si) _ ~ ~Si) ~Si) Dual system 6 hrs/160C 580 135 200 200 28060 -phenolic + 300 psi epoxy pressure Single coating 1 hr/170C 720 145600 350 580 480 bondable 300 psi ener-el of ¦pressure (b) A comparison of the heat transfer properties was made between the single coating of Example I and the dual coating as shown in Table 1. The results indicate that the presence of glass flbers provides an lmprovement of 20-30 percent in heat transfer character-lstics of the single coat bonded laminations over the dual coating s ystem .
(c) Bonded segments using the enamel of Example I were then tested to determine the dielectric properties. These results were then compared to unbonded phenolic resin maintained under pressure and simulating the conditions present in the stator core.
The results tabulated below indicate that an improvement is obtained using the epoxy enamel of F.xample I.
108~573 17GE-2454 ! ` ` ~-, Dielectric Strenqth .
Average Intarlaminar Dielectric Strength Coating System (volts to failure) :
Unbonded-cured phenolic 137 volts Bonded-cured epoxy of Ex. I 170 volts .... ' . ~. -' " ;, It will be appreciated that the invention is not limited to the ,;,~
specific details shown in the examples and illustrations and that various modifications may be made within the ordinary skill in the art without departing from the spirit and scope of the invention.
':
curing agent for the resin which provides latency at room temperature and coupled with a cure at elevated temperatures, a glass fiber spacer filler having a diameter of about 0.45-0.55 mil ln an amount sufflcient to provide uniform separation and insulation between the segments, lnorganic fillers to provide a working viscosity and maintain the glass fiber homogeneously dispersed in the resin, and a suitable solvent for application of the coating. Thereafter the solvent is removed from the coated segments, the dried and tack-free coated segments are stacked in a configuration of an element for forming a substantlal portion of or the entire stator core and the element is pressed and cured under condltlons of temperature and pressure to form an lntegral bond between the segments. Another aspect of our invention relates to an lntegrally bonded stator core for a generator comprislng a series of secJments of steel each of which is bonded to and insulated from an adjacent segr:lent, and an interlayer between the segments for bonding and insulatiny the segments, the interlayer being a thermally cured epoxy resin and a glass fiber filler having a uniform diameter of about 0.45-0.55 mll to provlde uniiorm separation and insulation between the segments.
The laminations or segments are approximately 0.010 to 0.030 inch thick and are stamped from a suitable grade of magnetic - ~ - _ . . .. . .. .. .
, "
:
"`` lO~S'~3 steel strip stock and then appropriately heat treated and coated with a thin inorganic coating, e.g., 0.10-0.25 mil coating of magnesium phosphate to keep the laminations separated prior to use. This coating has been designated as C-10 by the steel manufacturer. The segments are like a series of flat cards which are pie-shaped so that they may be stacked on key bars at the outside diameter and the inside diameter has slots in which the stator winding is later assembled as shown in Figure 3 of the J. G. Quinn patent cited hereinabove. While the surfaces of a segment appear normally smooth and regular, under magnifi-cation the surfaces are really quite irregular and there appear to be elevations or peaks and depressions or valleys. Attempts to form laminations using a single coating of an ordinary bonding composition between the segments having a critical thickness of about 0.5 mil are not possible because of the increased probability of laminates becoming shorted together due to the surface irregularities.
Reference will be made hereinafter to the accompanying drawings, in which:
Figure 1 is a schematic sectional view of a generator, Figure 2 is a view of a group of bonded laminations, Figure 3 is an enlarged sectional view taken through several laminations, showing the coating according to the invention, and Figure 4 is an enlarged portion of Figure 2, referred to as "Surface Section A".
As we have mentioned above the stator core of a large dynamoelectric generator may contain as many as several hundred thousand segments. The coating on the top and on the bottom of each segment of such an enormous machine has been critically defined as about 0.45-0.55 mil. The generating equipment is designed and built for high reliability and long life. Thus, factorsSuch as the interlayer between laminations must be extremely precise. Since the inorganic coating on each side of a segment is about 0.10 mil, the remainder or about 0.35-0.45 mil is the thickness of the insulating adhesive.
The insulating adhesive comprises about the following composition:
--`-- 1084573 Inqredient Broad Ran~e (wt.%) Preferred (wt.%) Epoxy resin 30-35% 30.4-31%
Curing agent up to 4% 1.6-2.3%
Accelerator up to 1% about .8%
Glass fiber spacer 10-25% 10.3-20%
Inorganic filler 10-25% 16.1-21.8%
Organic solvent 25-40% 30.5-35.2%
Any of the conventional epoxy resins having 1, 2-epoxy groups are useful in connection with the present invention. These resins are commercially available and have the general formula:
O O
/ \ /\
I. CHz-CH-Y-CH-CH2 wherein Y is the residue of the reaction product of a polyfunctional halohydrin, such as epichlorohydrin, and a polyhydric phenol. These reslns are well known and commerclally available. Typlcal phenols useful ln the preparatlon of the resin are resorcinol and various bisphenols resultlng from the condensatlon of phenol with aldehydes and ketones such as formaldehyde, acetaldehyde, and acetone.
Representative of the bisphenols is 2,2'-bis(p-hydroxyphenyl)propane (known as Bisphenol A); 4,4'-dihydroxydiphenylsulfone; 4,4'-dihydroxy-2 0 biphenyl; 4, 4 ' -dihydroxydiphenylmethane; 2, 2 ' -dihydroxydiphenyl-oxide, etc.
The epoxy resin useful for most applications in the practice of the present invention corresponds to the general formula:
, II CH2 CH-CH2 O~)R~OCH2 CH-CH1~
I I
LO~)R~OCH~CH-CH2 wherein R is a divalent radical selected frorn the group consisting of saturated alkylene radicals of from 1 to 8 carbon atoms, oxygen, and the sulfone group, y is 0 or an integer having a value up to 25 and n :
is 0 or 1. Specifically, R may be methylene, ethylene, propylene, isopropylene, isopropylidene, butylene, isobutylene, etc.
The most common epoxy resin of this type is the reaction . ~ :
product of epichlorohydrin and Bisphenol A which corresponds to the structural formula:
/H\CH CHfO~C~OCH2CH-CH~L~
CH3 OH I .
--O~)C~OCH / \ "~
wherein y has the meaning given above.
The instant epoxy resins may also be epoxy novolac resins, which are available commercially as CIBA ECN resins. These are derived from an ortho-cresol-formaldehyde novolac which is then reacted with epichlorohydrin to form a polyepoxide. Representative epoxy novolac resins correspond to the formula:
2 2 ~ O CH2 CH CH2 ¦ O CH2 CH CH2 ~CH2~ CH~
wherein y has the value given above.
An epoxy resin which is formed from tetraphenylol ethane and epichlorohydrin is also suitable. An intermediate from which this resln is prepared is illustrated by the formula:
V . -CH2--CH-CH2 0-CH2--CH-CH2 H CH
1 \ ~ /\ ; ' ' ''.' , ,.~,,l The instant epoxy resin may be liquid or solid. It generally has an epoxy equivalent in the range of 100 to 4000 and preferably from 150 to 500. The ep~xy equivalent weight is the weight of resin in grams which contain one gram equivalent of epoxy.
' ,~ ; ' '' ' ''` ., - "" 1084573 ~\ 17GE-24s4 - Curing agents for conventional type epoxy resins are disclosed by S. Oleesky and G. Mohr, Handbook of Reinforced Plastics, Reinhold, New York, pages 74-75. Most of the curing agents described are undesirable for the present application because they promote too rapid cure at room temperature and have a short pot life. The critefia for a desirable curing agent for laminating the large number of segments are that the agent must require elevated temperature for cure and must impart a long pot life. One useful system ls disclosed by M. Markovitz, U. S. patent 3,776,978 which dlscloses a mixture of a phenol and an organic titanate. Also probably useful are those designated as latent curing agents, such as boron trifluoride-monoethylamine complex, triethanolamine borate which have long pot lives and are cure activated by heat; and acid anhy~'.ides, such phthalic anhydride, and mixtures of pyromellitic dianhydrlde and maleic anhydride which require elevated temperature cures .
A preferred curlng agent for the epoxy resins employed herein ls dlcyandiamide having the structure:
NH
Curing can occur through all four nltrogen-containing functional groups. An advantage of dicyandiamide, when used with solid diglycidyl ether of Bisphenol A for laminating applications, is that it ` `
provides latency at room temperature coupled with rapid cures at 145 - 165C. For solid resins, it is normally used in a solvent such as acetone-water, dimethyl formamide or a glycol ether. When ' I; ' '' ' 1 ;; 1' ~ j -~` 1084S73 1 7GE~2 454 thoroughly milled or dissolved into the epoxy system, it will provide a one-container system stable for at least 6 months. While the amount of curing agent can vary to some extent, I have found that an effective amount generally is in the range of about 2.5-7.5 parts by weight per 100 parts of epoxy resin. The preferred concentration of the curing agent for a diglycidyl ether of Bisphenol A resin is about 4 . 7 parts by weight.
Optionally, the adhesive coating composition employing the preferred dicyandiamide curing agent incorporates an imidazole accelerator, especlally a substituted imldazole. These compounds may be represented by the general formula:
R2_ Ic ' R
whereln Rl, R2, and R3 are independently selected from the group conslstlng of hydrogen, lower alkyl, phenyl and lower alkylphenyl.
Particularly useful accelerators in this class are the following compounds:
Imidazole 2 -ethyl-4-methylimidazole l -benzyl-2 -methylimidazole 2 0 l-methylimidazole 1, 2 -methylimidazole ~ r The accelerator in very small amounts serves to decrease ~ -the curing time without a significant sacrifice of shelf life. Thus, 108~S73 -enough of the accelerator should be added to substantially decrease the curing time and not an excessive amount which produces gelation or imparts poor shelf life. An effective amount of imidazole accelerator is about 0.1-0.5 part by weight per 100 parts of epoxy resin, with the preferred amount being about 0.24 part by weight. -- A critical aspect of our invention is the use of fiber spacers which provide a uniformly spaced, positive separation between segments under the conditions of heat and pressure required during curing. The cYlindrical shape of the fibers is highly significant, since once the resin is dried, the fibers must stay locked in place.
In contrast spherical bodies would tend to shift locations during application of heat and pressure. Any of a number of glass ffbers, for example, conventionally available may be used and these include E-glass (silicate glass) and S-glass (magnesium aluminosilicate glass). These glasses can be manufactured to form fibers of great uniformity in diameter whlch provide uniform spacers. The fiber dimensions in addition to uniformlty are very significant: the dlameter should be about 0.50~0.05 mil (12-14 microns) and the length should be about 1/64 to 1/32 inch (400-800 microns). Fiber glass yarn within the prescribed diameter ranges are described by Oleesky and Mohr, previously cited, page 124 as the following:
Product Min . (in . ) Max (in . ) J 0. 00045 0. 00050 K 0 . 00050 0 . 00055 The amount of fiber glass spacers required to l)rovide uniform separation and insulation of the segments is about 10 to 25 percent ` 10~4573 , `' ' , 17GE-2454 by weight of the total adhesive composition. When the amount of fibers is in excess of 25 percent by weight, there is no improvement in separation, but clumping of the fibers occurs together with - tapering. When there are too few fibers, less than about 10 percent by weight, the dielectric strength is penalized with earlier failure and shorts occurring.
The fibers must be uniformly distributed in the adhesive coating sGlution and also on the surfaces of the segments. As a matter of fact deposition across the lamination phase should be so unlform that a monolayer of fibers is obtained without clumping.
Once the fibers are applied they must be relatively fixed in place without sliding on the surfaces of the laminates.
Other lnorganic fillers play an important role in the lnstant coating composition. These fillers are added to stabilize the overall composition, control the viscosity, and maintain the fibers ln suspension. An illustration of such a filler is a hlghly dlspersed slllca avallable commerclally under the trademark Aerosll OX 50 from Degussa Inc., which is produced from silicon tetrachloride ln a flame hydrolysis process with oxygen-hydrogen gas. It has BET
surface area of 50+15 m2/g, an average primary particle size of 40 millimicrons and a bulk density of approximately 80 g/l. Addltional suitable fillers are fumed silica, sold under the name of CAB-O-SIL
(L5) by Cabot Co., and a silica known as MIN-U-SIL sold by Pennsylvania Glass Sand Corp. which has a particle size of about 15 mlcrons. The amount of these other fillers is typically up to about 10 percent by weight and usually in the range of 6-10 percer.t by weight of the total composition.
`` :1084S73 The coating formulation involves a combination of solvents ; and thinners. The uncured epoxy resin is soluble in oxygenatedsolvents, such as ketones, esters and ethers, and in highly halo-genated hydrocarbons. Fast evaporating solutions are based on low boiling ketones such as acetone and methyl ethyl ketone.
The thinners are employed to reduce costs and to regulate viscosity.
I:)etermination of proper solvent balance is somewhat of an art and improper selection will cause difficulties. A proper solvent blend will hold in the curing agent, while providing a continuous fflm.
One typical blend for a diglycidyl ether of Bisphenol A consists of:
Parts Xylene 32 Methylisobutyl ketone 32 B Cellosolve ~ 32 lS Cyclohexanol 4 After the coating has been applied to the segments, the solvent is removed at temperatures up to about 300F for a short residence time of up to about 60 seconds. The dried coatlng is tack-free and remains reactive for bonding for an extended period of time, e.g., four months. Then the coated segments are stacked in a configuration of an eleme ~t for forming a portion or the entire stator core. The element is thereafter pressed and cured at elevated temperatures and pressures. Examples of curing schedules are in a range of about a temperature of 150-170C, a pressure of 200-300 psi and for a period of time of about 1-7 hours. The curing temperature depends to a large extent on the curing agent used to crosslink the ~ ~r2~~ Qr~
~. ' , ' . , .
~084573 17GE-2454 epoxy resin. The optimum curing schedule for a particular agent can readily be determined by routine experimentation by a person skilled in the art.
; Our invention is further illustrated by the following examples:
EXAMPLE I
An adhesive-insulating coating was prepared from the following formulation:
IngredientPart by weight Araldite* 6060 Epoxy resin 31 Dicyandiamide 1.6 2-Ethyl-4-methylimidazolen . 8 (10% solution in cellosolve) Cellosolve* 30.5 MIN-U-SIL 8.1 Aerosil* OX 50 8.0 Glass Fibers (1/64' long, 20.0 0.50 mil dia.) The Araldite* epoxy resin is a diglycidyl ether o~ Bisphenol A.
This composition was dispersed to form a homogeneous enamel for application to the metal segments.
EXAMPLE II
Another adhesive insulating coating was prepared from the following formulation:
*Trade Mark ~ ~084573 17GE-2454 Ingredient Parts by weight Epoxy cresol novolac resin21.1 (ECN 1280) Epoxy novolac resin (DEN 438) 2.3 Tyzor* OG/BRZ-7541(1.1) 2.3 Epoxy resin (Epon 1002) 7.0 Cellosolve* 17.6 n-Butylcellosolve 17.6 Cab-0-Sil fumed silica 10.3 Glass fibers (1/32'long, 10.3 0.50 mil dia.) Min-U-Sil microsilica 11.5 The curing agent Tyzor* OG/BRZ-7541 was tetraoctylglycol ` titanate/phenol formaldehyde novolac containing 2 to 3 phenolic OH groups per molecule. This composition was dispersed to form a homogeneous enamel for application to the metal segments.
EXAMPLE III
Silicon steel punchings manufactured by Allegheny Ludlum Co. and coated with a 0.10 mil coating of magnesium phosphate were then coated with the enamel of Example I to a thickness of about 0.35 to 0.45 mil. The segments were ~; 20 stacked, pressed and cured as shown below. The bond strengths in psi were determined.
(a) A comparison was made to a dual coating system in which the segments were initially coated with an insulating phenolic resin and thereafter coated with an epoxy resin containing no glass fibers. The results as shown in the table below indicate that superior bond strength is obtained by the single bondable coating of our invention.
B
- ~ ~
.
Bond Strength Retention as a Function of Thermal Aging _ 6 0 da ys 15 0 days Initial Aged at Aged at as 180C and 150C and Coating Cure Tested_ tested @ ¦ tested ~_ System Schedule R.T. 130C R.T. 130C R.T. 130C
_ ~Si) ~Sl) ~Si) _ ~ ~Si) ~Si) Dual system 6 hrs/160C 580 135 200 200 28060 -phenolic + 300 psi epoxy pressure Single coating 1 hr/170C 720 145600 350 580 480 bondable 300 psi ener-el of ¦pressure (b) A comparison of the heat transfer properties was made between the single coating of Example I and the dual coating as shown in Table 1. The results indicate that the presence of glass flbers provides an lmprovement of 20-30 percent in heat transfer character-lstics of the single coat bonded laminations over the dual coating s ystem .
(c) Bonded segments using the enamel of Example I were then tested to determine the dielectric properties. These results were then compared to unbonded phenolic resin maintained under pressure and simulating the conditions present in the stator core.
The results tabulated below indicate that an improvement is obtained using the epoxy enamel of F.xample I.
108~573 17GE-2454 ! ` ` ~-, Dielectric Strenqth .
Average Intarlaminar Dielectric Strength Coating System (volts to failure) :
Unbonded-cured phenolic 137 volts Bonded-cured epoxy of Ex. I 170 volts .... ' . ~. -' " ;, It will be appreciated that the invention is not limited to the ,;,~
specific details shown in the examples and illustrations and that various modifications may be made within the ordinary skill in the art without departing from the spirit and scope of the invention.
':
Claims (13)
1. A bonded stator core, for a dynamoelectric machine, which comprises (a) a multiplicity of steel segments stacked in the configuration of said core, each segment of at least a portion of said core being bonded to and insulated from the adjacent segment and (b) an interlayer between said segments for bonding and insulating said segments, said interlayer comprising a cured epoxy resin and a fiber spacer filler, said filler comprising cylindrical fibers having a diameter of 0.45-0.55 mil and a length of about 1/64-1/32 inch to provide uniform separation between the individual segments.
2. The stator core of claim 1, wherein said core is integrally bonded.
3. The stator core of claim 1, wherein the segments of only a portion of said core are bonded.
4. The stator core of claim 1, wherein said fiber spacer filler is glass.
5. The stator core of claim 4, wherein said fiber spacer filler is a silicate glass.
6. The stator core of claim 4, wherein fiber spacer filler is a magnesium aluminosilicate glass.
7. The stator core of claim 4, wherein said epoxy resin is a diglycidyl ether of Bisphenol A.
8. The stator core of claim 4, wherein said epoxy resin is an epoxy novolac.
9. The bonded stator core of claim 1, wherein the amount of the fiber spacer filler is about 10-25 percent by weight of the interlayer.
10. A method of forming a bonded stator core of a large turbine driven generator comprising the steps of (a) forming steel stator core segments having an inorganic coating thereon;
(b) applying an insulating adhesive coating on to both sides of the segments, said coating comprising a mixture of (1) an epoxy resin, (2) a curing agent for said resin which provides latency at room temperature coupled with a cure at elevated temperature, (3) a fiber spacer filler, said filler comprising cylindrical fibers having a diameter of 0.45-0.55 mil and a length of 1/64-1/32 inch in an amount sufficient to provide uniform separation and insulation between said segments, (4) an inorganic filler to provide a working viscosity and maintain the fiber filler homogeneously dispersed in the resin and, (5) a suitable organic solvent for application of the coating;
(c) removing the solvents from the coated segments;
(d) stacking the dried coated segments in the configuration of an element for forming at least a substantial portion of the stator core; and (e) pressing and curing said element under condition of temperature and pressure to form a bond between said segments.
(b) applying an insulating adhesive coating on to both sides of the segments, said coating comprising a mixture of (1) an epoxy resin, (2) a curing agent for said resin which provides latency at room temperature coupled with a cure at elevated temperature, (3) a fiber spacer filler, said filler comprising cylindrical fibers having a diameter of 0.45-0.55 mil and a length of 1/64-1/32 inch in an amount sufficient to provide uniform separation and insulation between said segments, (4) an inorganic filler to provide a working viscosity and maintain the fiber filler homogeneously dispersed in the resin and, (5) a suitable organic solvent for application of the coating;
(c) removing the solvents from the coated segments;
(d) stacking the dried coated segments in the configuration of an element for forming at least a substantial portion of the stator core; and (e) pressing and curing said element under condition of temperature and pressure to form a bond between said segments.
11. The method of claim 10 wherein the fiber spacer filler is glass and the amount of said fiber spacer filler in the coating is about 10-25 percent by weight.
12. The method of claim 11, wherein fiber spacer filler is a silicate glass.
13. The method of claim 11, wherein the fiber space filled is a magnesium aluminosilicate glass.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US71344076A | 1976-08-11 | 1976-08-11 | |
| US713,440 | 1976-08-11 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1084573A true CA1084573A (en) | 1980-08-26 |
Family
ID=24866153
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA284,191A Expired CA1084573A (en) | 1976-08-11 | 1977-08-05 | Lamination of stator core punchings |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS5330706A (en) |
| CA (1) | CA1084573A (en) |
| DE (1) | DE2733987A1 (en) |
| ES (2) | ES460709A1 (en) |
| FR (1) | FR2361767A1 (en) |
| GB (1) | GB1574986A (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4765054A (en) * | 1983-08-11 | 1988-08-23 | Black & Decker, Inc. | Method of making a field subassembly |
| DE3829068C1 (en) * | 1988-08-25 | 1990-01-11 | Mannesmann Ag, 4000 Duesseldorf, De | |
| JPH1189130A (en) * | 1997-09-08 | 1999-03-30 | Minebea Co Ltd | Motor construction |
| KR100785276B1 (en) * | 2005-12-29 | 2007-12-13 | 한국전기연구원 | Permanent magnet excited transverse flux motor with out-rotor |
| DE102006055264A1 (en) * | 2006-11-23 | 2008-05-29 | Robert Bosch Gmbh | Lamella laminated core for electrical device i.e. electrical machine, has set of lamella sheet metals stacked on each other, where lamella sheet metals consist of two lamella segments that are arranged next to each other |
| DE102008002106B4 (en) | 2008-05-30 | 2019-06-27 | Seg Automotive Germany Gmbh | Silenced electric machine |
| DE102012005795A1 (en) * | 2012-03-14 | 2013-09-19 | Kienle + Spiess Gmbh | Disc pack and method for its production |
| CN103326480A (en) * | 2013-06-21 | 2013-09-25 | 山东鑫孚矿业科技有限公司 | Motor stator formed by overlaying mucilage glue |
| EP3181609A1 (en) * | 2015-12-18 | 2017-06-21 | General Electric Technology GmbH | A support for end windings of an electric machine |
| DE102018122047A1 (en) * | 2018-09-10 | 2020-03-12 | voestalpine Automotive Components Dettingen GmbH & Co. KG | METHOD AND DEVICE FOR CONNECTING SHEET PARTS TO SHEET PACKAGES |
| DE102019113290A1 (en) * | 2019-05-20 | 2020-11-26 | Thyssenkrupp Steel Europe Ag | Method for producing an electromagnetic component, in particular a laminated core, for example a stator core or a rotor core, for an electrical machine |
| CN113432560B (en) * | 2021-05-26 | 2024-05-28 | 中安华力建设集团有限公司 | Indoor detection device for tunnel segment installation and positioning |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1293990A (en) * | 1961-07-03 | 1962-05-18 | Licentia Gmbh | Process for gluing sheets of electrical machines |
| CH391071A (en) * | 1962-03-01 | 1965-04-30 | Bbc Brown Boveri & Cie | Laminated stator bodies for electrical machines, in particular turbo generators |
| US3389006A (en) * | 1964-05-18 | 1968-06-18 | Armco Steel Corp | Process for forming a refractory coating on silicon-iron stock |
| CH460927A (en) * | 1966-08-05 | 1968-08-15 | Oerlikon Maschf | Process for gluing magnetic sheets and application of the process for tube generators |
| SE334934B (en) * | 1966-12-21 | 1971-05-10 | Asea Ab | |
| DE2130773A1 (en) * | 1970-07-02 | 1972-04-13 | Iskra Zd Za Avtomatizacijo V Z | Adhesive for gluing with a precisely determined distance |
| DE2145553C3 (en) * | 1971-09-11 | 1979-07-19 | Loi Industrieofenanlagen Gmbh, 4300 Essen | Process for the production of laminated cores for the field-leading parts of electrical machines and devices |
| CA1004596A (en) * | 1972-03-30 | 1977-02-01 | Fmc Corporation | Method of stabilizing dichlorocyanuric acid salts |
| CA999404A (en) * | 1973-05-03 | 1976-11-09 | Clayton N. Whetstone | Laminated magnetic material and method of making same |
| JPS5060705A (en) * | 1973-10-01 | 1975-05-24 |
-
1977
- 1977-07-13 ES ES460709A patent/ES460709A1/en not_active Expired
- 1977-07-28 DE DE19772733987 patent/DE2733987A1/en not_active Withdrawn
- 1977-08-05 CA CA284,191A patent/CA1084573A/en not_active Expired
- 1977-08-09 JP JP9470677A patent/JPS5330706A/en active Pending
- 1977-08-09 FR FR7724563A patent/FR2361767A1/en not_active Withdrawn
- 1977-08-11 GB GB3382577A patent/GB1574986A/en not_active Expired
-
1978
- 1978-05-30 ES ES470339A patent/ES470339A1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| ES470339A1 (en) | 1979-02-16 |
| FR2361767A1 (en) | 1978-03-10 |
| GB1574986A (en) | 1980-09-17 |
| DE2733987A1 (en) | 1978-02-16 |
| JPS5330706A (en) | 1978-03-23 |
| ES460709A1 (en) | 1978-11-16 |
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