Silicon steel sheet

Cores are built from high-grade grain-oriented silicon steel sheet, cut and stacked so the flux path stays tight and no-load loss stays low. The core is clamped as one unit rather than assembled loose, so it holds its geometry through transport and long service.

Conductive rod

Current-carrying rods and leads are made from high-conductivity copper, which cuts resistive heating at the joints and keeps the unit stable under continuous load. Terminations are tightened to a controlled torque so contact resistance does not drift over time.

Insulation system

Windings are insulated with mineral insulating oil and a matched insulation set. The combination slows oil ageing and keeps dielectric strength where it needs to be across the unit's service life, rather than only at the moment of factory test.

Transformer box

The tank is formed from standard high-grade steel plate profile and finished with corrugated walls that stiffen the shell while adding cooling surface. It is built to hold its shape in outdoor service, not only in a controlled room.

Customized service

Units are configured to the project rather than picked from a shelf: capacity, voltage combination, tapping arrangement, protection and finish are confirmed item by item before production starts. Overseas orders are packed and documented for their destination, and the delivery schedule follows the site programme.

After-sales service

EN — Support runs through the same engineering team that configured the unit: installation and commissioning guidance, fault diagnosis, and coordination of replacement parts. Response arrangements and contact channels are agreed with the project at order stage, so the person on site knows who to reach.

Body assembly

EN — The core-and-coil assembly is clamped with single-piece electrical-grade laminated wood blocks, moulded as one unit without joints, which keeps insulation strength high and absorbs the shocks of long-distance transport and rough road conditions. Leads are multi-strand flexible copper wrapped in insulation, so they flex under vibration instead of cracking.

Anti-corrosion upgrades

Corrosion protection starts with the steel rather than the paint: stainless fasteners so nothing seizes after years outdoors, a multi-stage surface pretreatment before any coating is applied, and a powder coating system selected for the corrosivity of the destination site. Rounded contours where panels meet the frame help the coating hold at the edges, and protective sleeves are fitted at the lifting points so the finish survives handling and loading.

Longnice's oil-immersed transformer works carries the full production flow on one site: core cutting, coil winding, body assembly, tank fabrication and surface treatment, oil filling, routine testing and export packing. The product range covers distribution and power transformers from 30 kVA to 31,500 kVA at voltage levels from 6 kV to 35 kV, together with box-type substations and high- and low-voltage complete switchgear. Windings are copper throughout and matched to low-loss laminated cores. Tank walls are corrugated for stiffness and natural oil circulation, with no fans, pumps or other moving parts in the cooling path. The core-and-coil assembly is clamped with single-piece electrical-grade laminated wood and wired with multi-strand flexible copper leads. Tanks are built for outdoor service with stainless fasteners, multi-stage surface pretreatment and a coating system matched to the destination's corrosivity. Every unit is configured to the project before production starts: rated capacity, voltage combination, tapping range of ±5% or ±2×2.5%, vector group, protection and finish are confirmed item by item. The 17 mainstream specifications from 50 kVA to 2,500 kVA cover the most frequently specified capacity range for power companies, EPC contractors and commercial projects. Export orders ship in wooden cases with nameplate and documentation prepared for the destination, on a delivery schedule that follows the site programme. The engineering team that carried out the configuration stays with the order after shipment, covering installation, commissioning and spares.