Inside the Transformer Production Process: From Core Cutting to Final Testing

Time：2026-01-28    Auther：ZTelec-www.ztelectransformer.com

Transformers are essential components of modern power systems, and their quality and reliability directly influence power supply safety and operational efficiency. From material selection to final inspection, each manufacturing stage plays a critical role in determining transformer performance. This article provides a comprehensive overview of the transformer production process, covering core manufacturing, winding fabrication, assembly, insulation treatment, and final testing.

Core Manufacturing

Selection and Pre-Treatment of Silicon Steel Sheets

Transformer cores are typically manufactured using cold-rolled grain-oriented silicon steel sheets known for high magnetic permeability and low core losses. Before processing, these materials undergo strict inspections to ensure their electromagnetic properties meet design specifications and efficiency requirements.

Core Cutting and Stacking

Precision cutting is carried out using CNC cutting equipment, shaping silicon steel sheets into configurations such as E-type, I-type, or C-type laminations. After cutting, the sheet edges are carefully deburred and coated with insulating layers to minimize eddy current losses.

During stacking, a staggered lamination method is applied to reduce magnetic reluctance and core losses. In some designs, thin insulating materials are placed between layers to further enhance electrical isolation.

Core Fastening and Grounding

Once stacked, the core is secured using insulated fasteners. A dedicated grounding system is installed to prevent static charge accumulation and ensure safe operation during service.

Winding Production

Conductor Selection and Pre-Treatment

Based on transformer capacity and application, copper or aluminum conductors are selected. The conductors are coated with multiple layers of insulation materials, such as paper insulation, enamel coatings, or composite insulation systems, to ensure dielectric strength and thermal stability.

Winding Fabrication Process

Low-voltage windings are generally wound first, using spiral or layered structures to achieve compact design and uniform current distribution. High-voltage windings typically adopt disc or continuous winding structures to withstand higher electrical stress.

Automatic winding machines are employed to ensure precise tension control and consistent winding geometry, effectively reducing inter-turn gaps and mechanical stress.

Insulation and Curing Treatment

Additional insulation materials are applied between winding layers and turns. Vacuum pressure impregnation processes are then used to enhance insulation strength, improve heat dissipation, and increase overall winding durability.

Assembly and Accessory Installation

After core and winding production, the transformer enters the assembly stage, where dimensional accuracy and process control are strictly enforced. The windings are assembled onto the core to form the active part of the transformer.

For oil-immersed transformers, the active part is installed into the transformer tank, while dry-type transformers are fitted with protective enclosures. Key accessories such as bushings, tap changers, temperature monitoring devices, and protective components are installed according to design specifications.

Vacuum Oil Injection or Casting Treatment

Oil-immersed transformers undergo vacuum oil filling to eliminate internal air pockets and significantly enhance insulation performance. This process ensures uniform oil penetration throughout the insulation system.

Dry-type transformers are treated using epoxy resin vacuum casting or vacuum pressure impregnation techniques, improving resistance to moisture, dust, and environmental contamination. This stage has a direct impact on long-term operational stability.

Comprehensive Testing Procedures

Routine Factory Tests

Each transformer unit undergoes a series of routine tests, including turns ratio verification, winding resistance measurement, insulation resistance testing, no-load loss evaluation, and load loss measurement. These tests confirm compliance with design parameters and manufacturing standards.

Type Tests and Sampling Tests

Type tests are performed on selected units to validate design performance. These include temperature rise tests to simulate full-load operation, lightning impulse tests to assess surge withstand capability, and sound level measurements to evaluate operating noise.

Special Tests

For specific applications, additional tests may be conducted, such as short-circuit withstand tests to verify mechanical strength under fault conditions and partial discharge tests to detect potential insulation defects.

Final Inspection and Factory Preparation

Before delivery, each transformer undergoes final visual inspection and cleaning. Nameplates and identification markings are installed, and all technical documentation, including test reports, operation manuals, and installation guidelines, is compiled.

Protective packaging and transportation measures are then applied to ensure the transformer arrives at the installation site in optimal condition.

From core cutting to final testing, every stage of the transformer manufacturing process directly influences product quality and reliability. Standardized production procedures and strict quality control ensure transformers meet the demanding requirements of power utilities, industrial facilities, and renewable energy projects.

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