Huanghua Group Co., Ltd. 
Epoxy Resin CastDry Type Transformer
Product Overview
CNHK’s HK SCB series is a dry-type Epoxy Resin Cast dry typetransformer. Due to the coil being encapsulated with epoxyresin, it is anti-ignite, fireproof, explosion-proof, maintenancefree, pollution-free, small in size, and can be directly installedin the load center. At the same time, scientific and reasonabledesign and pouring process make the product have lesspartial discharge, low noise, and strong heat dissipationability, Under forced air cooling conditions, it can operate fora long time at 140% of the rated load and is equipped withan intelligent temperature controller. It has functions suchas fault alarm, over temperature alarm, over temperaturetrip, and black box. It is connected to a computer through anRS485 serial interface and can be centrally monitored andcontrolled.
Type Designation
General Specifications
| Parameter | Specification |
| Product Type | Cast Resin Dry-Type Power / Distribution Transformer |
| Rated Power | 30 kVA – 3150 kVA |
| High Voltage (HV) | 10 kV / 20 kV / 35 kV (Um = 36 kV class, max. for dry-type) |
| Low Voltage (LV) | 0.4 kV / 0.69 kV / 0.8 kV / 6.3 kV / 10.5 kV |
| Frequency | 50 Hz / 60 Hz |
| Insulation Class | F (155°C, limit 120°C rise) / H (180°C, limit 145°C rise) on request |
| Cooling | AN/AF (Forced-air with fans, +40% overload) |
| Vector Group | Dyn11 / Yyn0 / YNd11 |
| Short-Circuit Impedance | 4% / 6% (std.) |
| Enclosure Protection | IP20 / IP23 / IP31 / IP54 (stainless steel enclosure optional) |
| Climatic / Env. / Fire Class | C2 – E2 – F1 (per IEC 60076-11, full special test package) |
| Standards | IEC 60076-11 / IEC 60076-3 / IEC 60529 |
| Eco-Design | EN 50629 referenced (dry-type energy performance) |
Engineering & Design Excellence
1 Cast Resin Winding System
The defining differentiator of this series is the vacuum-cast epoxy resin encapsulation applied to both HV and LV windings.
HV Winding: Copper wire or foil conductor, layer-wound, vacuum-cast with cycloaliphatic epoxy resin in a controlled temperature/humidity environment. The resin penetrates all interstices, creating a monolithic, void-free insulation body.
LV Winding: High-conductivity copper foil (or aluminum foil on request), interleaved with premium Nomex®/DMD insulation. Foil geometry yields inherently low axial short-circuit forces and superior current distribution.
Partial Discharge: Optimized mold design and vacuum degassing yield PD ≤ 5 pC (typical at 1.5 × Ur), critical for long-term dielectric integrity in indoor environments.
2 Core
High-grade grain-oriented silicon steel (CRGO), step-lap stacked, clamped in a rigid steel frame.
Core bolts insulated; yokes decoupled from clamps to suppress circulating currents.
3 Thermal & Overload Performance
AN mode: Rated load continuous, designed for 100 K rise (F-class) or 125 K (H-class).
AN/AF mode: Forced-air fans engage automatically at thermal setpoint; 140% rated load sustainable for limited duration (per IEC 60076-11 thermal cyclic capability).
Winding temp. indication (PT100 sensors in HV/LV hotspots) + alarm/trip contacts standard.
4 Enclosure & Environmental Rating (C2–E2–F1)
Per IEC 60076-11 Edition 2, Huanghua dry-types are validated for:
C2 – Climatic: Thermal shock (−25°C → +140°C), 100% humidity 144h, pass dielectric after.
E2 – Environmental: Condensation + salt fog / polluted atmosphere endurance (coastal, underground, industrial).
F1 – Fire Behavior: 60-min fire test (alcohol flame + 24 kW radiant panel per IEC 60332-3-10):
This C2–E2–F1 triad qualifies the transformer for hospitals, data centers, metro tunnels, offshore platforms, and any “people-dense + fire-sensitive” installation.
Efficiency & Loss Data
Dry-type eco-design in the EU market references EN 50629 (energy performance of large power transformers, extended by industry practice to medium dry-type). For the non-EU market, losses are specified per IEC 60076-11 and aligned with national efficiency tiers.
Dielectric Ratings (BIL per Voltage Class)
Unlike oil-immersed units, dry-type BIL is constrained by air clearance and resin thickness. Huanghua ratings per IEC 60076-11 / IEC 60076-3:
| System Voltage | Power-Freq. Withstand (1 min) | BIL (Lightning Impulse, full wave) |
| 10 kV | 35 kV | 75 kV |
| 20 kV | 50 kV | 125 kV |
| 35 kV (Um 36 kV) | 70 kV | 170 kV |
All units receive power-frequency induced voltage test as routine. Lightning Impulse (LI) is conducted as type test per IEC 60076-3; LI witnesses available per customer request.
Routine & Type Tests (per IEC 60076-11)
Routine Tests (every unit)
Winding resistance measurement (all taps)
Turns ratio & vector group verification
Power-frequency induced voltage withstand
No-load loss & current (at rated voltage)
Load loss & impedance (at rated current, 120°C ref)
Partial discharge measurement (typical ≤ 5 pC @ 1.5Ur)
Winding temperature sensor calibration (PT100)
Type / Special Tests (design-verified, reported)
Lightning Impulse (LI) – BIL per voltage class
Temperature Rise Test – AN & AN/AF modes
Short-Circuit Withstand – per IEC 60076-5 (mechanical + thermal)
C2 / E2 / F1 – Climatic, Environmental, Fire Behavior (IEC 60076-11 Ed.2)
Sound Level – per IEC 60076-10 (typical ≤ 52 dB(A) for 1000 kVA)
Target Applications
| Sector | Fit Rationale |
| Data Centers | Oil-free, AN/AF 140% overload, PD ≤ 5 pC, IP54 enclosure |
| Hospitals | F1 fire class, silent operation, indoor placement |
| Commercial High-Rise | Load-center siting, no fire pump/oil containment pit required |
| Metro / Railway | C2–E2–F1 certified, compact footprint, 20kV/35kV available |
| Wind Tower (LV side) | 0.69/0.8 kV step-up, vibration-resistant, maintenance-free |
| Offshore / Platform | C3/C4 corrosion prep + E2 + F1, epoxy fully sealed |
| Industrial (mining, cement) | IP54 enclosure, dust-proof, no oil leak risk |
