Investigations on Magnetization Characteristics of Transformer Models with Single-Phase Four-limb Core Composed of Different Grades of Steel Sheets

An experimental investigation of magnetization characteristics of single-phase four-limb transformer in laboratory is presented in this work. The waveform distortion properties of induced voltages and exciting currents during magnetization process are discussed. Using recursive least squares method, the adverse effects of trend term on flux calculation are effectively eliminated. The comparisons of magnetization characteristics of eight transformer models with single-phase four-limb cores which are produced by various grades of steel sheets are performed. In addition, the characteristics of hysteresis curves and basic magnetization characteristics of different transformer models relevant to various grades of steel sheets are analyzed. The experimental results show that odd harmonic is the main factor causing the distortion of exciting current and induced voltage. Additionally, the transformers composed of steel sheets with high magnetic induction such as 27RK090, 27SQGD090, etc. have better magnetization characteristic than of steel sheets with large no-load loss coefficient such as B27P100, 30QG105, 30SQG105, etc. The obtained results can provide valuable information for transformer core design.