The 250 kVA Dry Type Transformer acts as the modern standard for commercial building power, effectively bridging the gap between legacy specifications and current IEC requirements.

In many regions historically following NEMA standards, the 225 kva dry type transformer was the default specification. Our 250 kVA model serves as the direct metric (IEC) replacement. By selecting this unit, facility managers gain approximately 11% additional continuous power capacity within the same installation footprint. This extra headroom is invaluable for handling the "creep" of added electrical loads over the building's lifespan without requiring an early transformer upgrade.

When evaluating different types of transformer for indoor use, the decision often centers on fire risk management. As a true air insulated dry type, this unit utilizes ambient air as the primary cooling and dielectric medium between windings, supported by high-temperature solid insulation (Nomex or Aramid paper).

• Zero Fire Load: Unlike oil units that contain hundreds of liters of flammable fuel, this air-insulated design creates almost no fire load. It eliminates the need for fire suppression sprinklers or blast walls in the electrical room, significantly reducing civil engineering costs.
• Flashover Protection: The spacing between the HV and LV coils is rigorously calculated to prevent flashovers through the air gap, even under humid conditions, maintaining high Impulse Withstand capabilities (BIL).

Since the active part relies on air circulation, the external enclosure plays a critical role.

• IP23 Standard: We typically house the 250 kVA core and coil in a ventilated steel enclosure rated at IP23.
• Physical Barrier: This rating ensures that while cooling air can enter (at a <60° angle), the unit is protected against vertical water drips (e.g., from ceiling condensation) and the ingress of solid objects larger than 12mm (preventing rodents or accidental finger contact with live parts).

Close-up of IP23 ventilated steel enclosure protecting 250 kVA

dry type transformer coils.

250 kVA dry type transformer core and coil fully assembled inside protective steel enclosure.

Item	Specification
Rated Power	250 kVA (Metric Standard)
Equivalent Legacy Rating	Covers 225 kVA demand
Primary Voltage	4160V / 6.6kV / 11kV
Secondary Voltage	400V / 480V / 208V
Insulation System	Air Insulated (Class H/220°C)
Cooling	AN (Air Natural)
Enclosure Rating	IP21 (Indoor) or IP23 (Drip-proof)
Efficiency	> 98.5% (at 50% load)
Type	Three Phase Cast Resin Dry Type Transformer
Frequency	50Hz / 60Hz
Phase	Three Phase
Vector Group	Dyn11, Dyn1, Yyn0, Customized
Winding Material	Copper / Aluminum
Insulation Class	Class F (155℃), Class H (180℃)
Cooling Method	AN / AF
Temperature Rise	100K / 120K
Impedance Voltage	4% or Customized
HV Tap Range	±2×2.5% or Customized
Enclosure Protection	IP23 / IP54 / IP55
Installation	Indoor / Outdoor
Standard	IEC 60076-11, IEC 60076 series

 

250 kVA dry type transformer core and coil fully assembled inside

protective steel enclosure.

• Educational Facilities: Installing in schools or universities where safety regulations strictly prohibit liquid-filled transformers indoors.
• Office Retrofits: Replacing aging 225 kva dry type transformer units in older office blocks with a modernized, higher-capacity unit.
• Light Manufacturing: Powering assembly lines where the load profile is steady and non-polluting.

250 kVA dry type transformer installed in a university facility for

safe power distribution.

Advanced Manufacturing Process for 250kVA Cast Resin Dry Type Transformer

Our 250kVA dry type transformer is manufactured through a controlled production process to ensure electrical reliability, mechanical strength, and long service life. Each manufacturing stage is inspected according to strict quality requirements before final delivery.

1. Silicon Steel Core Manufacturing

High-quality grain-oriented silicon steel sheets are precisely cut and stacked to reduce magnetic losses and improve transformer efficiency. The core assembly process ensures accurate dimensions, low vibration, and stable electromagnetic performance.

2. Copper Winding Production

High-conductivity copper conductors are processed using advanced winding equipment to achieve uniform coil structure and excellent short-circuit resistance. The winding dimensions and insulation distances are carefully controlled according to design requirements.

3. Epoxy Resin Vacuum Casting

The HV and LV windings are encapsulated with high-quality epoxy resin under vacuum conditions. This process eliminates air bubbles and improves insulation strength, moisture resistance, and mechanical protection.

4. Core and Coil Assembly

The completed windings are assembled with the transformer core and fitted with insulation components, temperature sensors, terminals, and accessories. Every assembly step is checked to ensure correct alignment and electrical safety.

5. Final Inspection and Testing

Before shipment, each transformer undergoes comprehensive factory testing, including electrical performance verification, insulation testing, ratio testing, and visual inspection.

Through strict manufacturing control, we ensure every 250kVA cast resin transformer meets customer specifications and international quality requirements.

 

Quality and reliability are essential requirements for transformer projects worldwide. Our 250kVA cast resin dry type transformers are manufactured under strict quality management procedures and designed to meet international electrical standards for safe, efficient, and long-term operation.

With a focus on continuous quality improvement, environmental responsibility, and manufacturing consistency, our production system follows internationally recognized management standards. Certification documents and technical compliance reports can be provided to support customer approval, project evaluation, and tender requirements.