Binarşîna û Xasîyên Tîxnikî ya Tranformatorên Paşînî di Her Çeşnakî de

1960an dekên navînê, transformatoran sêkanî çendina yên bi destûrên Class B în birindarên vekirinên serbexer hatîn. Modeli hilbera wê SG nîşan kir. Lêgerîna ku cîlanên bixweber nehat dît, cîlanên gerîsîne yên sêwistan derbasdar dihêve û di şeklên berdewam an spiral de dibandin, wekî lê cîlanên bikaranîn ên di şekil discî de dibandin. Kablên bi karibîn hatin jî bi hêsanên dubareyên glass fiber an kablên yekane bi hêsanên glass fiber û pîlak alkyd.

Yekêtiya komponentên dindest ûter hatin ji malên phenolic glass fiber. Prosesa impregnation hatiye bilî varnishên insulation Class B li ser cîlanên bikaranîn û sêwistan di temperatûra ambient û presûra xwehata dike, di nav de bi seretina medium-temperature (ji bo ku temperatûra nehatêve bibînin 130°C). Transformatora sêkanî vê tîpa, hewceyek da ku li ser transformatoran bi petrolan rêjandina tenê ye, di rastina fire resistance pir zelatî, lê di rastina resistance'ê ya moisture û pollution da nayê piştguhîk çêkir.

Bun Destûrê, prodûksiyonê ya vê tîpa hate kesandin. Lê, dizayniya besereka electric, magnetic, û thermal, bi taybetmendiya layout structureyê, fundemaqîn solid ên bişeyî hatiye girîng kir ji bo piştgiriya transformatoran sêkanî yên insulation Class H nûyan bi destûrên Class H.

Di Amerîka de, hîndewa wan prodûsêran, wek FPT Corporation di Virginia de, transformatoran sêkanî bi karibîn material aramid NOMEX® ji DuPont û malên insulation biafirandin. FPT du model prodûkti hatiye pêşkirin: FB type, ji bo insulation system rated at 180°C (Class H), û FH type, ji bo 220°C (Class C), ji bo coil temperature rises of 115K (125K in China) û 150K, demal. Cîlanên sêwistan bi karibîn foil an multi-strand layered windings, turn-to-turn û layer-to-layer insulation bi NOMEX®.

Cîlanên bikaranîn ûn di şekil discî de, bi kablên bi hêsanên NOMEX® paper. Jî lêgerîna spacer blocks navîn di navên coil discs, comb-shaped spacers hatin bikar bînin, ku ji bo dikarinîna peak voltage di navên discs û piştguhîkirina axial short-circuit strength ya cîlanên bikaranîn ên bermîn--lê vê prosesê complexity û manufacturing time biguherîne. Cîlanên bikaranîn û sêwistan hatin winding bi navên concentrically ji bo improve mechanical strength. Hindewa designs hatin bikar bînin malên NOMEX® insulation boards as spacers û blocks.

Insulation cylinders di navên high- û low-voltage windings hatin dibandin ji 0.76 mm thick NOMEX® paperboard. Impregnation process employs multiple cycles of vacuum pressure impregnation (VPI) followed by high-temperature drying (reaching 180–190°C). Di FPT de, transformatoran wê ji bo maximum voltage rating of 34.5 kV û maximum capacity of 10,000 kVA dibandin. Vebijarka wê UL certification in the United States hate girtin.

Di China de, hindewa transformatoran prodûsêran hatin bikar bînin materialên insulation NOMEX® ji DuPont û manufacturing specifications relevant (such as HV-1 or HV-2) along with Reliatran® transformer technical standards ji bo produce Class H insulated SG-type dry-type transformers, similar to FPT’s FB type. Lekin, ji bo FPT, domestic manufacturers typically impregnate only the coils rather than the entire transformer assembly. Although full-body impregnation provides better overall sealing, it is less visually appealing and requires all product testing to be completed prior to treatment. Additionally, the impregnating varnish is more prone to contamination, making coil-only impregnation a more practical and reasonable choice in the Chinese context.

Di Europe de, development of dry-type transformers has taken a more diverse path. In addition to epoxy resin vacuum casting and winding technologies, other types have emerged, including SCR-type non-cast solid-insulated encapsulated transformers and SG-type open-ventilated dry-type transformers similar to those in China. In the 1970s, a Swedish manufacturer developed open-ventilated dry-type transformers using NOMEX® insulation. Later, another manufacturer replaced NOMEX® with glass fiber and DMD, reducing material costs.

The coil structure resembled early Class B insulated products, with multi-strand or foil-wound low-voltage coils and disc-type high-voltage coils. Turn insulation was made of glass fiber, and spacers were ceramic. Other insulation components used modified diphenyl ether resin glass cloth laminates (for cylinders) or modified polyamide-imide laminated glass cloth boards (for cylinders), DMD, SMC, and similar materials. The coil processing method employed VI (vacuum impregnation) without pressure application during impregnation.

Key technical aspects of this process include the proper selection of impregnation varnish (resin) and process parameters, as well as the production of ceramic parts. Ordinary ceramics are brittle, unglazed, susceptible to moisture, and prone to cracking under uneven stress or thermal gradients. Therefore, they must possess very high density and hardness—qualities currently achievable only through imported materials.