Manufacturing Process of Voltage Transformer
Voltage Transformer Manufacturing Process
Inspect the R-shaped core for excitation performance, dimensions, tight winding, and absence of burrs, sharp edges, or rust. Wrap multiple layers of crepe paper, semiconductive insulating tape, and DMD insulation paper around the outer surface of the core to isolate it from the secondary winding.
Use a voltage transformer secondary coil winding machine to wind enamel wire onto the core. Insert DMD insulation paper between layers to ensure interlayer insulation. After winding, lead out the secondary leads, insert them into high-temperature sleeves to enhance insulation and secure the wire ends. Wrap the outer side of the secondary coil with semiconductor crepe paper as an overall insulating buffer layer to evenly distribute the electric field and reduce partial discharge.
Place an epoxy frame over the core with the completed secondary coil. Seal and fix the open end of the epoxy frame using insulating tape and apply internal shielding wrapping. Mount the core onto the core fixture of the voltage transformer primary coil winding machine and wind the primary coil, inserting PMP insulation paper between layers to ensure interlayer insulation.
After winding, test the coils for DC resistance, insulation resistance, turns ratio, and verify the number of turns. Reject non-conforming products for rework; pass products proceed to the next process.
After winding, install a shielding layer. Lead out the primary leads through high-temperature sleeves to strengthen insulation, weld terminals, and wrap an insulating layer over the primary winding. Secure the primary winding with supports and place insulating buffer material between the primary and secondary windings to ensure electrical clearance and insulation distance.
First, clean the casting mold thoroughly and spray a release agent inside the cavity. Allow it to stand for 20 minutes so that the release agent volatilizes and dries completely. Assemble and securely fix the coil and iron core into the mold, then lock the positioning fixture to ensure proper terminal placement and insulation clearance. Place the assembled mold into an oven for preheating and drying to remove moisture from within the coil.
Preheat and premix epoxy resin, hardener, and silica micro powder separately. Deeply mix the two-component epoxy resin and hardener independently under vacuum to degas. Strictly control material temperature to prevent premature gelation.
Push the mold into the vacuum casting tank, align the feeding port of the equipment with the mold inlet, and start feeding. The casting tank begins vacuum extraction and heating. When the vacuum level and temperature reach preset values, the pre-mixed epoxy resin and hardener are thoroughly blended through a static mixing system and poured into the mold under high vacuum. The mixture fully penetrates all gaps in the winding, eliminating internal voids.
After casting, transfer the mold together with the assembly into the oven for post-curing for 3–6 hours, following a stepwise temperature profile for gradual heating and constant-temperature curing. Staged temperature control reduces internal stress and prevents cracking of the cast body.
After complete curing and cooling of the mold, remove it. Trim the sprue port, flash, and burrs from the voltage transformer, and finish the exterior surface. Inspect the surface for cracks, voids, defects, or other flaws.
Conduct tests on the finished product including DC resistance measurement of windings, turns ratio, polarity, error and phase difference testing, insulation resistance test, power frequency withstand voltage test, partial discharge test, no-load current and volt-ampere characteristic measurement, as well as dimensional inspection. Reject non-conforming products; approve qualified items for storage.
Install baseplate, junction box, and terminal blocks. Print nameplates, clean, package, and store the products.
