Why Can Transformer No-load Tests Detect Core Defects?

In transformer manufacturing, the quality of the core is critical to equipment performance and energy efficiency. The primary role of the core is to transfer magnetic flux, and its performance directly affects the transformer's no-load loss and operational efficiency. During the Factory Acceptance Test (FAT) of transformers, no-load testing effectively identifies potential defects in the core, ensuring that its quality meets design standards.

The main purpose of the transformer no-load test is to measure the transformer's losses and current during operation at rated voltage without any load. No-load loss primarily consists of core hysteresis loss and eddy current loss, while the resistive loss caused by no-load current flowing through the winding is minimal. Therefore, variations in no-load loss primarily reflect defects in the core. For example, poor-quality insulation varnish between silicon steel sheets, causing local short circuits, can increase no-load loss by 10% to 15%. Additionally, insulation damage in core bolts or yoke beams can lead to increased eddy currents, localized overheating, and further loss increases.

To ensure core quality, transformer manufacturers should implement the following measures:

1. Accurate Measurement of No-Load Loss: Utilize high-precision measuring equipment to monitor no-load loss values and analyze deviations from design specifications to identify potential core defects.  
2.Core Temperature Rise Detection: Use infrared thermal imaging or other temperature sensors to check for localized temperature rises in the core, enabling quick identification of defect areas.  
3. Material and Process Control: Conduct rigorous quality inspections on silicon steel sheet materials and adopt automated stacking technology to ensure precision and consistency in core assembly.  

4. Enhanced Insulation Treatment: Apply high-quality insulation varnish to silicon steel sheets and strengthen the insulation of core bolts and clamps to prevent local short circuits during operation.

JYW6100 Transformer No-loads and On-loads Tester