New Electric Insulating Materials for the Insulation Systems of Rotating Electrical Machines

ISSN 1068-3712, Russian Electrical Engineering, 2007, Vol. 78, No. 3, pp. 149 155. Allerton Press, Inc., 2007. Original Russian Text A.V. Papkov, A.P. Mel nichenko, V.M. Pak, I.E. Kuimov, 2007, published in Elektrotekhnika, 2007, No. 3, pp. 45 51. New Electric Insulating Materials for the Insulation Systems of Rotating Electrical Machines A. V. Papkov, A. P. Mel nichenko, V. M. Pak, and I. E. Kuimov Abstract A wide range of nomenclature and properties for new materials for the insulation of high voltage electrical machines and traction motors of F and H insulation classes developed at Elinar Holding Company are presented in the report. DOI: 10.3103/S106837120703011X For more than half a century, the Elinar Holding Company (Elinar HC) has been producing and supplying electric insulating materials (EIM) for the production and repair of insulation systems for all types of rotating electrical machines, ranging from turbo and hydrogenerators to asynchronous electric motors for general industrial construction. The organizational structure of the company represents a vertically organized holding which includes both the enterprises that produce EIM (the CJSC Elinar Factory of EIM, the LLC Elinar Plast, and the Elinar- West GMBKh) and the enterprises that manufacture the primary components for EIM production (the JSC Astrakhan Glass Fiber and the LLC Muscovite). The EIM produced by the Elinar HC are used in many electrical machine construction and repair plants in Russia and the CIS, as well as in Germany, France, Spain, Belgium, Italy, the Czech Republic, Finland, and in the countries of Asia. The Elinar HC is a member of the International Association Interelectromach, the International Association Electrokabel, and the European Association of EIM producers. This paper presents the results of the company s work on the exploitation, perfecting, and development of EIM production for the last two years. ELECTRIC INSULATING MATERIALS FOR THE INSULATION SYSTEMS OF TURBO AN HYDROGENERATORS AND HIGH VOLTAGE ELECTRIC MOTORS Preliminarily impregnated glass mica tapes of class F heat resistance, which are presently being produced by the HC under the trademark Elmicatherm 1 52409 and 55409 for the technology of manufacturing insulation by hot pressing, and which were designated as Elmicatherms at their introduction, are highly compet- 1 is a registered trademark of the JSC Elinar Holding Company. itive with the world s leading producers of EIM based on their technological characteristics. The introduction of Elmicatherm thermoreactive insulation enabled the following: A high, long-term electric strength for frame insulation was ensured; The value of the dielectric dissipation factor at high temperatures was considerably decreased, and, in this way satisfied the stringent requirements regarding testing time (with a duration of up to 400 h) under the simultaneous influence of alternating fields with high strengths, an industrial frequency of 10 MV/m, and a temperature of 120 C at the insulation; Tolerance for the influence of thermocyclic loads under repeated changes in temperature at the insulation ranging from 40 155 C was ensured; the last two requirements are necessary at the export supplies of turbo and hydrogenerators; The real achievement of class F heat resistance in the insulation was ensured, which allows for the opportunity to raise the operating temperatures and, consequently, to decrease the machine dimensions, or, to increase unit power. The advantages of the Elmicatherm insulation permitted a toughening of the main standard of hydrogenerators, which normalizes the thickness of the winding insulation depending on the voltage. Additionally, the achievement of making the working gradient of the field strength on a winding equal to 3.0 MV/m was also accomplished. The successful application of new insulation in the place of basic micatherm insulation in producing the bar windings of turbo and hydrogenerators at JSC Power Machines in the Electric Power branch shows that Elmicatherms are fully suited to the requirements of high voltage insulation [1, 2]. However, powerful turbogenerators with air cooling, which are currently being designed, require higher quality electric insulating materials based on a range of indices for producing insulation for rotor and stator windings. 149

150 PAPKOV et al. Thermal conductivity, W/m K 0.4 0.3 0.2 75 100 125 150 175 200 225 T, C Fig. 1. The dependence of the coefficient of thermal conductivity of the insulation on temperature for variants: Elmicapor 533099-UT (impregnation in PK-11); LSKN 160 TT (impregnation in PK-11). Materials based on Nomex aramid paper (prepreg P-AKN), as well as rotary slot boxes based on glass fiber and aramid paper, have been mastered for rotor insulation. Class N materials are applied. It is important to increase the transmission of heat from a winding to a stator iron for the frame insulation of a stator winding. There are several engineering solutions for this purpose, including the following: to decrease the thickness of the stator winding frame insulation; to increase the thermal conductivity coefficient of insulation; to raise the temperature on a winding. The first solution requires having a frame insulation with a high value of electric strength, i.e., raising the gradient of field strength on a winding from the level of 3.0 MV/m as it is achieved on Elmicatherm to 3.5 MV/m. Table 1. The main characteristics of Elmicatherm 52 419 tape Nominal thickness, mm 0.14 0.18 Surface density, g/m 2 185 ± 25 260 ± 40 The contents of the components, %: mica, no less than 40 40 binding compound 36 ± 5 36 ± 5 volatile matter, no more 1.5 1.5 than Breaking load at stretching, 130 130 N/cm, no less than Electric strength, kw/mm, no less than 25 25 tanδ, no more than: in the initial state 0.02 0.02 at temperature of 180 C 0.10 0.10 The second solution is to apply insulation with an increased coefficient of thermal conductivity. The thermoreactive insulations Elmicatherm and monolith have a thermal conductivity coefficient of 0.28 W/m K. The third solution is to apply class N insulation. According to the data [3], the mica insulation with a thermal conductivity coefficient of 0.50 0.55 W/m K has been developed with the addition of inorganic solid particles. Filling materials are added in the course of producing untreated mica tape, while insulation is produced using a method of vacuum pressure impregnation. Research conducted on the creation of mica tapes with increased coefficients of thermal conductivity has resulted in the output of a development batch of untreated mica tape under the trademark Elmicapor 533199-UT. The tape was impregnated with the epoxy compound PK-11. The insulation was produced by the technology monolith-2. The insulation monolith-2 was produced under the same conditions on an LSKN-160TT serial tape. Figure 1 presents the dependence of the coefficient of thermal conductivity of the monolith-2 insulation on temperature. It should be noted that the achieved level of the thermal conductivity coefficient on the new tape being equal to 0.33 W/m K does not meet the set requirements, therefore current development is working toward obtaining a value of 0.4 0.45 W/ (m K). A development batch of a preliminarily impregnated Elmicatherm 52419 tape intended for application to class N frame insulation in stator windings has been developed and produced. The main properties of the tape are presented in Table 1. The tape is intended to produce the insulation through hot pressing using existing technological equipment. The new tape is presently being tested. An untreated Elmicapor 523119 mica tape containing a modified polyethyleneterephthalate film in its composition has been developed. The work was carried out with the purpose of increasing the electric strength of the frame insulation. The role of the polyethylene terephthalate film in increasing the long-term electric strength at its introduction into mica composition is known [4]. In the course of the long-term exploitation of insulation, PET-E film may undergo partial detachment from the substrate, although this effect has not been discovered in practice until now. Therefore, before producing the untreated mica tape, the PET-E film was, in this experiment, modified in a plasma of smoldering, low-frequency discharge in order to increase adhesion to contacting surfaces. The main indices of the elmilapor 523119 tape are given in Table 2. Ten dummies with a calculated insulation thickness of 2 mm were made in order to carry out the testing of the tape (10 layers were created that were half of the width of the tape with the film placed on top). The dimensions of the copper were 6 30 800 mm. Cop-

NEW ELECTRIC INSULATING MATERIALS FOR THE INSULATION SYSTEMS 151 Table 2. The main characteristics of untreated Elmicapor 523119 tape Thickness, mm 0.10 ± 0.02 0.11 ± 0.03 Surface density, g/m 2 130 ± 12 140 ± 14 Mass share of components, g/m 2 mica (calcined muscovite) 65 ± 4 65 ± 4 glass fiber cloth 27 ± 3 38 ± 4 PET-E film 28 ± 2 28 ± 2 binding compound 10 ± 3 10 ± 3 Breaking load at stretching, N/cm >80 >130 Mass share of accelerator, mg/m 2 360 ± 80 360 ± 80 Breakdown voltage, V >5.0 >5.0 Rigidity, N/m <45 <50 Table 3. The geometric dimensions of the insulation in the rod dummies after vacuum pressure impregnation Model No. Average dimensions before impregnation, mm Average dimensions after impregnation, mm Thickness of the finished insulation, mm 30 9.5 9.9 2.0 44 10.0 2.0 55 9.7 10.1 2.0 98 10.1 2.1 100 9.9 1.9 104 9.6 10.0 2.0 118 9.6 10.1 2.0 The average value 2.0 Table 4. The dependence of insulation tanδ on Elmicapor 523119 tape on temperature and voltage Model No. 20 C 130 C 155 C 2 kv 4 kv 6 kv 8 kv 2 kv 4 kv 6 kv 8 kv 2 kv 4 kv 6 kv 8 kv 98 0.33 0.43 0.49 0.55 4.84 4.92 5.01 5.12 6.74 6.88 7.18 7.30 141 0.35 0.37 0.46 0.54 4.72 4.79 4.91 5.00 6.71 6.82 7.20 7.25 Table 5. The measurements of the partial discharge of rod dummies with insulation on Elmicapor 523119 tape Model No. d, mm Parameter U test, MV/m 16 12 8 4 2 98 2.05 U max, mv 920 900 800 5 5 U average, mv 40 33 18 0.3 0.3 q pd, pc 1012 990 880 6 6 I pd, mka 2.68 2.21 1.21 0.02 0.02 141 2.1 U max, mv 660 700 660 6 5.6 U average, mv 29 24 13 0.3 0.3 q pd, pc 726 770 726 7 6 I pd, mka 1.94 1.61 0.87 0.02 0.02 per bus bars were insulated on a laboratory machine. The wide and narrow facets of the dummies were banded with plackets. The dummies then underwent vacuum pressing impregnation in compound PK-11 in the operation mode for the monolith-2 insulation. The geometrical dimensions of the rods and the thickness of the insulation are given in Table 3. The values of tanδ at temperatures 20, 130, and 155 C were determined on the prepared rod dummies (Table 4). The partial discharge values measured at field strength 16 MV/m are given in Table 5. To test the insulation for long-term electric strength, the rod dummies were made on Elmicapor 523119

152 PAPKOV et al. F(t) 99 50 10 5 1 10000 100000 1,00E+6 t, s Fig. 2. The distribution of time Weibull before insulation breakdown at E = 15 MV/m, 50 Hz for variants: on Elmicapor 523119 tape (variant 1 β 1 = 5.51, η 1 = 6.04E + 5); on LSKN-135 SPl tape (variant 2 β 2 = 2.28, η 2 = 3.57E + 5). R, Ω/ 1.0E + 12 1.0E + 11 1.0E + 10 1.0E + 09 1.0E + 08 1 2 3 4 5 6 7 kv/cm Fig. 3. The dependence of electrical resistance of LPP-1000 tape on constant electric field strength. tape and LSKN-135SPl serial tape containing nonmodified PET-E film in a mica composition. Figure 2 presents the graphs of the long-term electric strength distribution of the insulation that were processed by Weibull, as well as the graphs of the time values before the insulation fault. Testing the insulation of the rod dummies on the Elmicapor 523119 tape shows the following: tanδ has low values up to temperature 155 C; the growth of tanδ has a minimal value; the levels of partial discharge correspond to the norms for high voltage insulation; the nonfailure operating time before insulation breakdown at the 63% probability level amounts to 168 h on Elmicapor 523119 tape and 99 h on LKSN-135SPl tape. Thus, the long-term electric strength of Elmicapor 523119 tape on modified PET-E film essentially increases the value of serial tape LKSN-135SPl. At present the Elmicapor 523119 tape is being tested on full-sized turbogenerator rods. The JSC Elinar Holding Company produces a tape under the trademark LPP-400 for the antidischarge defense of the slot parts of the windings for high voltage electric motors and turbo and hydrogenerators. An LPP-1000 tape characterized by nonlinear current voltage is presently being offered for the antidischarge defense of end windings. The tape can be applied to the technology through both hot pressing and vacuum pressure impregnation. THE MAIN CHARACTERISTICS OF LPP-1000 SEMICONDUCTING TAPE The main characteristics of LGSH-1000 semiconducting tape Thickness, mm 0.20 ± 0.02 Breakdown force at rupture 50 (in the longitudinal direction), N/cm, no less than Relative lengthening 20 (in the longitudinal direction), %, no less than Surface resistance at electric 1000 field strength of 5 kv/cm, MΩ/ 2 Type of substrate layer Fibers from the shrink polyester thread (warp) and glass fiber (weft) The LPP-1000 tape is impregnated with a rapidly solidifying epoxy binding agent. The properties of epoxy resin remain stable for approximately 30 min at 120 C. The tape completely hardens after maintaining for 1 h at 140 C or 2 h at 120 C. The tape shrinks during heating in the longitudinal direction, permitting a winding insulation to be obtained without folds or wrinkles. Figure 3 shows the dependence of the electrical resistance R (Ω/ ) on the electric field strength E (kv/cm) following the solidification of the binding agent (1 h at 140 C). Over the last several years, a new direction has been developed at Elinar HC in the production of electric insulating materials involving the mastering of the pro- 2 is the unit of area.

NEW ELECTRIC INSULATING MATERIALS FOR THE INSULATION SYSTEMS 153 Table 6. The main properties of rotary groove boxes Index KPT-R (F) KPT-R (H) KPTB-R (F) KPTB-R (H) PPT-C (F) (semiconducting) The breaking stress during the transverse 280 280 250 250 250 bending of the layers at a temperature of 23 C, MPa, no less than The breaking stress during the transverse 112 100 100 bending of the layers at a temperature of (180 ± 5) C, MPa, no less than The electric strength transversely to the 12 12 20 20 20 layers at a temperature of 23 C in transformer oil, kv/mm, no less than The specific electric strength, Ω cm* transversely to the layers 1 10 3 1 10 6 parallel to the layers 1 10 1 1 10 3 Resistance to short-term heating, C, no less than 200 250 200 250 180 Table 7. The construction of a class H heat resistance insulation system for a continuous current traction motor Type of insulation Designation of EIM Class of heat resistance Anchor winding Winding wire PSDKT (additional coil insulation is required) or PPIPK-2 Turn insulation Elmicatherm 529029 Tape 0.08 20 H Frame insulation Elmicatherm 529029 0.10 20 Tape H Slot insulation Imidoflex 292 0.17 or Sintoflex 818 0.17 H Cover insulation Tape LES-P 0.10 20 H Bar-to-bar insulation of a collector KIFE-N 1.2 Elmicaplast 1440 1.2 H Collector baffles Elmicaform 325 0.25 Elmica 325 PM 0.25 H Layer insulation Elmica 425 0.32 H Serving Tape LSBE-180 H Slot wedge ST-ETF H Sealant compound Mastic MET-180 H Impregnating compound Compound Elkom -180 H Balance coil Frame insulation Elmicatherm 529029 Tape 0.08 20 H Main pole coils Interturn insulation (layer insulation) Elmicaflex 4450 0.25 H Frame insulation Tape Elmicatherm 529029 0.10 30 H Layer insulation Elmica 425 0.3 H Impregnating compound Compound Elkom -180 H Sealant compound Mastic MET-180 H Cover insulation Tape LES-P 0.20 30 H Auxiliary pole coils Interturn insulation (layer insulation) Elmicaflex 4450 0.25 H Frame insulation Elmicatherm 529029 Tape 0.10 30 H Layer insulation Elmica 425 0.3 H Impregnating compound Compound Elkom -180 H Cover insulation Tape LES-P 0.10 30 H

154 PAPKOV et al. duction of KPTB and KPT trademark slot boxes intended for use in the slot insulation of the windings of rotors and turbogenerators with insulation systems of class F heat resistance. The production of L, S, and U-shaped boxes of slot rotors with KPTB-R and KPT-R marks for class F turbogenerators, H heat resistance, and slot semi-conducting boxes with the trademark KPPT-S for the stators of turbo and hydrogenerators has presently been mastered. The developed nomenclature and main technical characteristics of these boxes are presented in Table 6. ELECTRIC INSULATION MATERIALS FOR THE INSULATION SYSTEMS OF TRACTION MOTORS (TM) Over recent years the efforts of the company s technical specialists have been concentrated on the development and mastering of new EIM for the insulation systems of new engine traction motors (TM) in production. The construction of the TM insulation systems of class F heat resistance is presented in detail in [5]. This insulation system was tested in cooperation with the Department of Locomotive Economy of the JSC RZhD and the Direction of the JSC RZhD Zheldorremach during major repairs involving the replacement of the engine insulation of diesel and electric locomotives at the Ulan- Ude LVRZ, Rostov ERZ, Astrakhan TRZ, Ekaterinburg ERZ, and the Ussuri TRZ. More than 100 units of TM were repaired. The engines are presently being exploited following the major repairs and the guarantee run of 175 thousand km has been finished; there is no data on the breakdown of the modernized TM. In 2006, the insulation system underwent resource tests in the JSC VELNII (Novocherkassk) to prove the high reliability of the new insulation. The TM insulation system of class H heat resistance was developed simultaneously with the introduction of a developed insulation system of class F heat resistance. The insulation for the class H anchor and stator windings of drive motors is presented in Table 7. The suggested system of class H heat resistance was used by the FGUP VNIKTI MPS of Russia in developing the modernization project for the TED ED-118 of series A and B. Two drive motors were produced and are now undergoing accelerated tests in the institute s laboratories. The tests for the longevity of the given insulation system are being carried out simultaneously with this work at the JSC VELNII. A new impregnation compound, Elkom -180, of class H heat resistance developed at the JSC Elinar Holding Company was suggested for the given insulation system. MAIN TECHNICAL CHARACTERISTICS OF THE IMPREGNATION COMPOUND ELKOM 180 The conditional tenacity on the VZ-246 viscometer (with nozzle diameter of 4 mm) at a temperature of (40 ± 2) C, s, no more than The capability to dry up in a thick layer at a temperature of (155 ± 2) C, min, no more than The new production of finished goods from materials containing mica (such as baffles with the trademark MK and insulating cylinders with the mark TsI) for the collectors of direct current engines with class F insulation systems and H heat resistance has been organized in the JSC Elinar Holding Company. The baffles and cylinders represent goods having been extruded and heat treated in a furnace. They are made by molding the mica layers of the proper production. To improve the qualities of goods, different reinforcement filling materials (glass fiber cloths, aramid, polyester papers, and polymeric films) are introduced into the construction of baffles and cylinders, which allows the demands of electric machines producers to be satisfied completely. REFERENCES 100 The gelatinization time at a temperature 8 of (160 ± 2) C, min, no more than Cementing capacity, N, not less than: R; M (15 35 C) 45 75% 350 R; M (180 C) < 20% 200 Electric strength, MV/m, not less than: R; M (15 35 C) 45 75% 25 24 h (23 C) 93%; 20 M(15 35 C) 45 75% Specific volumetrical electrical resistance, Ω/m, not less than: R, M (15 35 C) 45 75% 1 10 13 1. Pipchuk, N.D., Pinskii, G.B., Petrov, V.V., et al., Development and Introduction of New Electric Insulating Materials and Systems of Thermoreactive Insulation of Turbo and Hydrogenerators, Elektrotekhnika, 2003, no. 4. 25 R, M (180 C) < 20% 5 10 8 24 h (23 C) 93%; M (15 35 C) 45 75% 5 10 11

NEW ELECTRIC INSULATING MATERIALS FOR THE INSULATION SYSTEMS 155 2. Azizov, A.Sh., Andreev, A.M., Kostel ov, A.M., and Polonskii, Yu.A., Development of High-Voltage Electrical Machines Insulation, Elektrotekhnika, 2007, no. 3. 3. Tari, M., Yoshida, K., and Sekito S., A High Voltage Insulating System with Increased Thermal Conductivity for Turbogenerators CWIEME 2001 Coil Winding Insulations and Electrical Manufacturing, Germany, June 26 28, 2001. 4. Drachev, A.I., Pak, V.M., Gil mann, A.B., and Kuznetsov, A.A., Increasing Long-Term Electric Strength of Compositional Electric Insulating Material with Polyethyleneterephthalate Film PET-E, Elektrotekhnika, 2003, no. 4. 5. Papkov, A.V., Mel nichenko, A.P., Pak, V.M., and Kuimov, I.E., New Electric Insulating Materials for Insulation Systems of Turbo and Hydrogenerators of Traction Motors, Elektrotekhnika, 2005, no. 3.