About Us


Hyosung’s cast resin transformer feature compact size, minimized power loss and noise, by adopting the latest design techniques.

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Our cast resin transformers are certified by ISO and CESI, an international certification authority. In 2008, we obtained the coveted seismic and vibration test (Q-Class) certificate, proving once more that our quality management and technical competence are unmatched.


Self-extinguishing characteristics of epoxy significantly reduces the spread and effect of a fire, and the possibility of explosion is nearly non-existent
Easy transportation and installation with simple structure
No toxic substance (oil or gas) discharged
Extended lifetime
Adopts a higher class epoxy resin
Epoxy Resin: uses H class epoxy resin, which is higher than the standard F class, as the main insulation material of the mold transformer to control thermal aging and extend the overall lifetime of the transformer by three-folds.
High stability and durability with strict quality management
Winding structure: when the radial build (RB) of the high-pressure winding is large, the temperature difference between the center and the surface of the winding gets higher, then crack in the winding may cause a partial discharge. Therefore, when the RB is large, an air duct is inserted making the RB thinner, then the temperature difference between the center and the surface is reduced and cracking is prevented.
When the air duct is inserted, the electric field distribution of the high-pressure winding becomes stable and the withstanding voltage becomes more resilient against external surge.
Casting process quality management: By strengthening quality management and interim examination of the casting process which determines the electrical and mechanical quality of the windings, the quality of casting by batch is checked (* Testing is required for checking how high the temperature is required to be for transiting from the solid glass-like elasticity of the solid polymer to the flexible rubber-like elasticity as well as checking the chemical combination status of the epoxy resin and process stability.)
By adopting the latest analysis technique, the transformer can be operated under severe conditions.
Satisfies the customers by resolving various failures and anomalies, which may occur in operation on site, through technical analysis and visiting the site when customers request after-service.

Installation Site

Where the installation condition is limited
Where fire prevention is required (Flame Retardancy)
Where customers request reliability
Transformer for special load: Inverter, converter, UPS system, electric arc furnace, variable transmission drive, electric welding device, industrial process control
Where the eco-friendly and environment-resistance is necessary
Common and public facilities: Condominiums, hotels, studio apartments, shopping malls, hospitals, and other public facilities
Manufacturing factories: Automobile factories, semiconductor factories, and chemical factories
Ships and renewable energy facilities: LNG ships, electric propulsion ships, and wind power generation systems
Special areas: Power plants (nuclear, water, fire, wind, and tidal), airports, subways, container cranes, and tunnel excavation work


Classification Description
Installation Area Indoor
Rated Voltage (kV) 1st Voltage and Tap Voltage 23.9F-22.9R-21.9-20.9-19.9 6.9F-6.6R-6.3-6.0-5.7
2nd Voltage 6.6/3.3 0.38-0.22 0.22-0.11 0.38-0.22
Phase 3ph 3ph 1ph 3ph
Standard Wiring △-△ △-Y 1ph, 3-wiring △-Y
Rated Capacity (kVA) 75 75 75
100 100 100
150 150 150
200 200 200
300 300 300
500 500 500
750 750 750
1,000 1,000 1,000
1,500 1,500 1,500
2,000 2,000 2,000
3,000 3,000 3,000
4,000 4,000 4,000
5,000 5,000 5,000
Frequency 50, 60Hz
Insulation Class Primary : F, B    Secondary : F, B
Increase in Winding Temperature Primary : 100°C, 80°C    Secondary : 100°C, 80°C
Dielectric Strength / Voltage Class 20kV 6kV 3kV 0.4kV or below
Power Frequency Withstand Voltage 50kV 20kV 10kV 3kV
 Impulse Withstand Voltage (BIL) 95/125kV 60kV 40kV -
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