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Dry-Type Transformer Manufacturing Process: Precision Design & Rigorous Production

Classification:

Industry News

Release time:

2025-07-07

Dry-type transformers are the preferred choice for modern power distribution systems, commercial buildings, data centers, industrial plants, and special environments (e.g., ships, tunnels) due to their exceptional safety (oil-free, flame-retardant, self-extinguishing), environmental friendliness, low maintenance, and superior operational stability. Behind this performance lies a foundation of meticulous scientific design and highly refined manufacturing processes. This article provides an in-depth analysis of the core production process of dry type transformer.

I. Precision Design: The Foundation of Performance & Reliability

Design is the critical first step in ensuring a dry-type transformer meets specific application requirements and achieves long-term reliable operation. It encompasses these key stages:

Requirements Analysis & Parameter Definition:

Precisely gather customer requirements: Input/output voltage levels, rated capacity (kVA/MVA), frequency, phases, insulation class (e.g., Class F, H), protection class (IP), cooling method (AN/AF), environmental conditions.

Define performance targets: Efficiency requirements, loss limits, impedance voltage, temperature rise limits, overload capacity, noise levels.

Type Selection:

Determine transformer type based on requirements: e.g., SCB series (epoxy resin cast), SG series (open ventilated), VPI (Vacuum Pressure Impregnated).

Select optimal structure: Rectangular or circular core, winding structure (layer, disc), tank design, and cooling solution (cooling ducts, fan configuration).

Electromagnetic Calculation & Optimization:

Main Parameter Calculation: Perform detailed electromagnetic field simulations to accurately determine core cross-section, magnetic flux density, primary/secondary turns, conductor size (copper/aluminum), current density.

Performance Prediction: Calculate no-load loss, load loss, impedance voltage, efficiency, temperature rise.

Iterative Optimization: Refine the design through repeated calculations and simulations, ensuring all parameters exceed standards and meet specific customer needs.

Thermal Design & Temperature Rise Control:

Precisely calculate hot-spot temperature rise in windings and core. Optimize cooling structure (duct layout, radiator design) to ensure temperature rise under worst-case conditions stays within the insulation class limit.

Structural design and Drawing output:

Complete detailed mechanical design: Core clamps, winding supports, lead arrangement, enclosure.

Generate full production drawings (electrical, structural, assembly) and Bill of Materials (BOM).

II. Rigorous Manufacturing: Where Process Defines Quality

Dry-type transformer manufacturing is a highly specialized process demanding strict control. Main steps include:

High-Standard Material Preparation & Inspection:

Strict Sourcing: Use premium materials: Grain-oriented silicon steel (low-loss), high-purity electrolytic copper or electrical-grade aluminum (conductors), high-performance epoxy resin (cast type) or high-temperature insulation varnish (VPI type), or equivalent premium insulation, fiberglass reinforcements.

Incoming Inspection: Rigorously test key raw materials (physical, chemical, electrical): e.g., core loss (silicon steel), resistivity (conductors), dielectric strength (insulation).

Core Manufacturing – Crafting the Magnetic Path:

Precision Cutting: Use high-accuracy slitting and cutting lines to shear silicon steel sheets to exact dimensions, strictly controlling burrs.

Stacking & Assembly: Employ step-lap or wound core techniques, precisely controlling stacking factor and air gaps. Securely clamp the core using high-strength frames and tie rods to ensure low noise and minimal losses.

Winding Fabrication – The Art of Insulation & Precision:

Coil Winding: Wind conductors (flat or round wire) onto forms using dedicated machines, strictly controlling tension and packing density according to design specs.

Insulation Processing (Core Technology):

Cast Coil (SCB): Place wound coils in molds. Inject epoxy resin compound under vacuum, ensuring complete penetration and bubble elimination. Cure under precisely controlled temperature to form a solid, sealed, moisture-resistant insulation block.

VPI / Open Wound (SG): Pre-dry wound coils. Perform Vacuum Pressure Impregnation (VPI) to deeply saturate winding interstices with high-temperature varnish. Follow with thermal curing. Open windings often require multiple impregnations/cures for enhanced strength and environmental resistance.

Termination Processing: Connect leads via welding or mechanical joints. Apply reliable insulation and secure terminations.

Assembly – Integrating Core & Coil:

Core Assembly: Precisely place cured HV/LV windings onto the core limbs.

Final Assembly: Install top/bottom clamps, insulation supports, lead brackets, tap changers (if applicable), temperature controls.

Lead Connection: Connect HV/LV leads to terminals/bushings reliably, ensuring proper clearances.

In-Process Inspection & Pre-Testing:

Conduct stringent inspections at critical stages (post-winding, pre-cast/VPI, post-assembly): Visual, dimensional, insulation resistance (IR), winding resistance (DC).

III. Comprehensive Testing: The Guarantee of Excellence

Finished transformers undergo rigorous testing to ensure compliance with design specs, international standards and customer requirements:

Routine Tests:

Insulation Resistance (IR) Test

Voltage Ratio & Vector Group Test

Winding Resistance Test (DC)

Power Frequency Withstand Voltage Test

Induced Overvoltage Withstand Test

No-Load Loss & Current Test

Load Loss & Short-Circuit Impedance Test

Partial Discharge (PD) Test: Crucial for detecting minute insulation defects, a key indicator of casting/VPI quality.

Type Tests (Per Standard/Contract):

Temperature Rise Test

Lightning Impulse Withstand Test

Sound Level Measurement

Special Tests (Customer Request):

Short-Circuit Withstand Test

IV. Quality Assurance System: The Lifeline Throughout

Advanced manufacturers implement ISO 9001 quality management systems, ensuring Total Quality Control:

Standardized Operations: Strict adherence to procedures and work instructions.

Traceability: Full traceability of key materials and processes.

Advanced Equipment: Utilization of automated, high-precision machinery (e.g., auto-winders, vacuum casting plants, PD testers).

Personnel Training: Ensuring skilled operators and inspectors.

V. Packing, Shipping & Installation

Protective Packaging: Cleaned, dried units packed with moisture-proof, shock-absorbing materials. Critical components (bushings, sensors) receive extra protection.

Clear Identification: Accurate nameplate data (parameters, weight, warnings). Packaging marked with lifting points, center of gravity, handling instructions.

Expert Shipping: Secure transport (road/sea) based on size/weight to prevent tipping and vibration damage.

On-site guidance: Provision of installation manuals. Optional on-site technician support for erection, connection, and commissioning.

Conclusion: Professionalism Forges Reliable Power

The exceptional performance of dry-type transformers stems from a highly specialized, standardized production flow: precise requirements analysis, rigorous electromagnetic and mechanical design, high-grade material selection, meticulous core and winding fabrication (especially epoxy vacuum casting or VPI insulation), culminating in comprehensive final testing (including critical Partial Discharge testing). Every controlled step ensures the delivery of a safe, reliable, energy-efficient, long-lasting power core, providing a solid foundation for the user's electrical system. Choosing a supplier with proven design expertise and strict manufacturing processes is paramount for ensuring long-term transformer stability.