What insulating materials are used for transformers
With the largest number of cardboard, as well as laminated wood, insulating paper, transformer oil, large oil-immersed transformers are mostly oil - paper insulation.
There are also NOMEX? insulation plates for the mat and the support structure. The insulation between high and low pressure is made of 0.76mm thick NOMEX? cardboard. Its impregnation process uses multiple VPI vacuum, pressure impregnation, high temperature drying (drying temperature of 180-190 ℃). At FPT, the highest voltage of this transformer is made to 34.5kV and the maximum capacity is 10000kVA. This technology is UL certified in the United States. Domestic transformer manufacturers use NOMEX? insulation materials and DuPont's manufacturing specifications (HV-1 or HV-2) and Reliatran Raytheon TM transformer technology standards such as the manufacture of H Type insulated SG-type dry-type transformers and the United States FPT's FB-type transformer has similarities, but the domestic product coil VPI impregnation process is different from the FPT company, it does not impregnate the entire transformer body, and only the coil impregnated. The whole body impregnated package integrity is good, but not only beautiful, but also in the processing must be done before the relevant product testing. Dipping paint is also easy to be filthy, relatively speaking in China the latter is more reasonable.
Some of the transformer plants in the United States, such as FPT in Virginia, have developed a NOMEX? Aromatic Polyamide using DuPont as a primary insulated dry-type transformer. FPT products are available in two models: FB type 180 ℃ (H level) of the insulation system. FH type 220 ℃ (C level) of the insulation system, the coil temperature rise were 115K (China 125K) and 150K. Its low-voltage coil is foil-type or multi-layer and laminated, and NOMEX? is used for both turn insulation and interlayer insulation. The high-pressure coil is a cake, and the wire is wrapped in NOMEX? paper. The barcakes do not have a conventional stay and a pad, and the comb is used to reduce the maximum voltage of the cake by half. The high-voltage coil of the axial short-circuit resistance, but increased the coil winding system and manufacturing time. High and low voltage coil for nesting, enhanced mechanical strength.
Dry type transformers before the 1960s are mainly B-type insulation of the open-type dry-type transformers, product model for the SG type. When there is no foil coil, the low pressure for the majority of multi-root and around the layer or spiral coil, high pressure for the pie coil. Wire for the double glass envelope or single glass fiber package enamel enameled wire. The rest of the insulating material is mostly phenolic glass fiber materials. The impregnation process for the room temperature, atmospheric pressure with B-class insulation impregnated paint were high and low pressure coil impregnation and drying at the temperature (drying temperature does not exceed 130 ℃). Although this dry-type transformers than oil-immersed transformers in the fire performance has made great progress, but its moisture, anti-pollution performance is worrying. Is no longer produced. Nevertheless, its successful electrical, magnetic, thermal calculations and structural design have laid a good foundation for the new H-class insulated open-ended transformers that have evolved later.
