CS276545B6 - Multi-layer sheet insulation of thermal grade F based on slim paper - Google Patents

Abstract

•The solution falls within the field of electrical engineering. Ξ It will be used to implement new winding designs with increased resistance to short-term thermal overload in five-transition states arising in low-voltage electrical machines. The purpose of the solution is to obtain an insulating material with higher long-term thermal resistance and higher thermal resistance during short-term overstressing. The essence of the solution is an insulator consisting of one layer of glass fabric and a layer of flexible mica paper, impregnated with a modified polymer binder and glued with a layer of PETP foil or PETP foil bonded to a polyester mat.

Description

The present invention relates to a multilayer sheet insulation of temperature class F based on mica paper, used for the production of groove insulation enabling the application of a new type of winding construction with increased resistance to short-term thermal overload in transients arising in a low voltage electric machine.

At present, to insulate the grooved part of the insulation winding between phases, such types of surface insulation materials are used, which, although classified in terms of temperature resistance according to international recommendations for a given temperature class, do not actually achieve technical parameters that would guarantee their sufficient service life. in technical practice for a given temperature use. these are mainly materials based on PETP (polyethylene terephthalate) film. Their main disadvantage is their low dimensional stability at operating temperature and a loss of mechanical properties even during lower long-term thermal stress. These insulations in normal operating modes and fault conditions of low-voltage electrical machines (overload until the overcurrent protection is switched off, which can be repeated several times) are not very resistant to overpressure by conductor jams, especially at the outlet of the groove, which often causes the motor insulation system to fail. due to a short circuit to skeleton. The disadvantages of these insulations are exacerbated by the use of some impregnating varnishes, the application of which is necessary for the insulation system of low-voltage electrical machines, but which worsen the insulation properties. insulation, resp. shrinkage causes it to crack. Cracks formed in the groove part increase the danger of an electrical cross-section between the winding and the frame. Due to the loss of ductility during operational aging, the groove insulation breaks or breaks at the point of exit from the magnetic circuit of the machine and ceases to fulfill its insulating function. Interphase and positional insulations from said insulating materials stratify and crack after loss of ductility during aging, thus disrupting the insulating system in the most temperature-exposed parts in the winding faces.

The present invention overcomes the above-mentioned disadvantages of the prior art multilayer sheet insulation of temperature class F based on mica paper, the essence of which consists in that it consists of a layer of flexible and thermally stable mica insulator weighing at least 100 to 200 g / m 2 based on glass electrical insulating fabric and mica paper pre-impregnated with a modified polymeric binder up to a content of 30% - 8% glued with a layer of PETP film with a basis weight of maximum 190 g / πι, which can be combined with a polyester mat with a thickness of up to 100 μm.

The use of the insulating materials according to the invention for the insulation of low-voltage machines eliminates mechanical deformations. The insulation material has a higher long-term temperature resistance compared to the produced flat insulators and, in addition, a significantly higher temperature resistance at short-term overload up to 250 ° C allowed by international IEC recommendations, e.g. temperature class F insulation system. This ensures a higher operational reliability of the electrical machine.

The insulating material according to the invention is suitably used as groove insulation in those electrical machines in which frequent switching and reversing occur which are accompanied by overvoltage stress degrading the system. Because the material is characterized by a higher pre-impregnability, which leads to an increase in the insulating state of the winding, this reduces the possibility of undesired overvoltage stresses on the components of the insulating system.

Surface insulators for temperature class F are mainly made of thermoplastic foils, hot-extrudable under increased thermal stresses. The multilayer insulator based on soft paper with a thermoset glass fabric can withstand even longer-term thermal overload at temperatures up to 250 ° C, and improves the temperature drop in the groove.

When repairing damaged windings, the groove insulation is easier to remove from the grooves of the electrical machine due to the use of a thinner foil to maintain the required thickness of the surface insulation and facilitates the repair.

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In the case of short circuits to the frame, the bracket insulation with the thermoplastic carrier melts due to high temperatures and an arc is formed between the frame and the winding at the melting point, which causes a part of the magnetic circuit of the stator or rotor. In the case of the use of groove insulation with a carrier made of glass cloth and mica paper, this phenomenon does not occur and the motor is usually repairable without disturbing the magnetic circuits.

NERS bracket insulation (N-polyester mat, E-polyethylene terephthalate foil, R-mica paper-remica, S-glass cloth) is more affordable compared to other types of thermosetting insulators. The compatibility of NEN and NE groove insulation with impregnating varnishes is lower than that of NERS groove insulation due to the fact that the foil material is attacked by solvents to an increased extent than inorganic glass and the mica of the NERS surface insulation in question.

The essence of the invention is further documented by specific examples of embodiments of a multilayer planar insulator.

Example 1

The sheet insulation material was prepared by gluing a foil mica insulator based on a glass electrical insulating fabric and an epoxy-polyurethane binder (epoxy equivalent of the epoxy component is 350 to 400, pour point 42 ° C), basis weight 160 g / nr and PETP film. The individual components were laminated at a temperature of 80 to 100 ° C on a laminator. The resulting product was perfectly glued and flexible. The insulating material was cut to the required size according to the shape of the groove and inserted into the stator or rotor bundles.

Example 2

The sheet insulation material was prepared by gluing a foil mica insulator based on a glass electrical insulating fabric and an epoxy-polyurethane binder (epoxy equivalent of the epoxy component is 350 to 400, flash point 42 ° C), basis weight 160 g / m ² and PETP film bonded to polyester mat with a varnish composed of epoxy and polyester components, the epoxy equivalent of the epoxy resin being 300 to 350, the flash point 36 ° C. The individual components were laminated at a temperature of 80 to 100 ° C on a laminator.

Basic physical-mechanical and dielectric properties of insulating materials:

Example 1 ERS 270/125 thickness / mm / 0.27 stiffness ’/ N / 90 tensile strength / N // 10 mm width185 tear resistance / N / 930 breakdown stress / kV / 20

Example 2 NERS 450/190 total thickness v / um450 PETR film thickness v / um190 thickness / mm / 0.44 stiffness / N / 90 tensile strength N / 10 mm width285 tear resistance N1 560 breakdown stress kV30

The implementation of the invention finds application in the following activities:

- for inflated windings of asynchronous motors up to an axis height of 355 mm,

- bracket insulation and intermediate windings for crane asynchronous motors, where thermoplastic grooved insulation NEN is the cause of their excessive failure,

- for unidirectional machines intended for spindle drives of machine tools,

- insulation for bandages of one-way machines replacing less flexible and more difficult to process laminates,

CS 276545 B 6

- insulating intermediate inserts for power and instrument transformers of temperature class F-H,

- insulation for traction motors.

Claims (2)

PATENT CLAIMS A multilayer temperature class F insulator based on mica paper, characterized in that it consists of one layer of flexible mica insulator with a basis weight of 100 o to 200 g / m, formed on the basis of glass electrical insulating fabric and mica paper preimpregnated with epoxy polyurethane binder with epoxy equivalent. of epoxy component 350 to 400, constituting 22 to 38% by weight, dry matter per total component and of polyethylene terephthalate film with a maximum thickness of 190 .mu.m. · T 2, A multilayer sheet insulator according to claim 1, characterized in that the polyethylene terephthalate film is joined to a polyester mat with a maximum thickness of up to 100 .mu.m.