EAF transformer quality appraisal

electric furnace transformer is based on the core principle of high-load power conversion and thermal stability synergy. By optimizing short-circuit impedance, load loss and cooling efficiency, it achieves the synergy of large current output, voltage regulation accuracy and long-term operation reliability. It is widely used in power supply systems for electric arc furnaces, submerged arc furnaces and special metal smelting. In steel smelting, it is used to accurately control the electrode current of electric arc furnaces; in ferrosilicon/carbide production, it meets the continuous high-load demand of submerged arc furnaces; in vacuum smelting, it ensures the stable output of high-frequency power supply. Compared with conventional power transformers, electric furnace transformers have strong short-circuit resistance, high overload capacity and excellent harmonic suppression. They are the core energy equipment of the metallurgical industry.

Zhongke Testing is a product quality appraisal service organization registered with the court. It can provide quality appraisal services for electric furnace transformers. It has a professional appraisal team and advanced instruments and equipment to provide fair and accurate appraisal results for the quality appraisal of electric furnace transformers.

With the upgrade of energy efficiency standards in the metallurgical industry, related quality dispute cases have increased significantly. The judicial dispute focuses on:

1, performance index dispute: load loss exceeds standard, temperature rise exceeds standard;

2, material defects: silicon steel sheet iron loss exceeds standard, winding copper purity is insufficient;

3, process problems: uneven insulation between winding turns, excessive cooling oil dielectric loss;

4, contract performance dispute: core configuration (such as imported silicon steel sheet brand, on-load tap-changer type) does not comply with the technical agreement.

The litigation quality appraisal technical methods of electric furnace transformers include:

1. Appearance inspection: Check the overall appearance, nameplate information, surface defects, etc. of the electric furnace transformer.

2. Insulation performance test: Use insulation resistance tester and high-voltage DC withstand voltage test device to conduct insulation performance test on the winding and insulation system of electric furnace transformer.

3. Short circuit impedance test: Use the transformer short circuit impedance tester to measure the short circuit impedance of the electric furnace transformer and evaluate the quality of its magnetic circuit and winding structure.

4. Load characteristic test: simulate the actual load conditions of the electric arc furnace, conduct a load characteristic test on the electric furnace transformer, and evaluate its voltage stability, temperature rise, loss and other performances.

A steel plant of the applicant signed an "80MVA Electric Arc Furnace Transformer Procurement Contract" with a manufacturer of the respondent, and it was agreed that the load loss should be ≤0.5%. After being put into operation, the measured loss reached 0.9%. The manufacturer argued that it was caused by the harmonic interference of the power grid.

identification analysis results:

The quality analysis expert group discussed and comprehensively analyzed the relevant information, contract technical agreements, on-site inspection case materials and other data of "Electric Furnace Transformer" and made the following quality scores Analytical opinion:

The iron loss of the silicon steel sheet of the electric furnace transformer involved in the case is 1.4W/kg (agreement ≤ 0.8W/kg), the winding DC resistance deviation is +8% (agreement ±3%); the tan δ value of the cooling oil is 0.6% (agreement ≤ 0.3%), and the dielectric loss exceeds the standard and the temperature rise reaches 78K.

The appraisal conclusion determined that defects in materials and insulation systems were the main cause of insufficient energy efficiency.

The electric furnace transformer quality appraisal report should include:

1, appraisal purpose (such as energy efficiency dispute attribution, safety compliance verification) and cited standards;

2, equipment model involved, technical agreement, operation and maintenance records;

3, testing method and equipment list ( Such as short circuit impedance tester, gas chromatograph);

4, detection data and failure correlation analysis (such as the impact of iron loss on load loss);