VP11-10 Performance of Oriented Si-steel and Fe-Based Amorphous Alloy Core Transformers under DC Bias
Creators: Mi Zou
Miaomiao Yang
Dong Yan
Tianhao Tang
Xianlun Tang
Publisher: name: IEEE
Year: 2025

Oriented silicon steel and Fe-based amorphous alloys are both widely used as iron core materials in power transformers. Silicon steel transformers (ST) offer good magnetic and electrical properties at a low cost. The amorphous transformer (AT) reduces 60% to 70% in no-load losses under sinusoidal excitation conditions compared to Si-steel core [1]. However, the performance of AT under DC bias remains less understood, despite the increasing occurrence of DC bias [2]. Existing literature primarily focuses on the magnetic and electrical properties of ST under DC bias [3]. Magnetic property research includes the frequency-dependent reluctance-based model [4], Preisach hysteresis modeling [5], and anisotropic magnetostriction measurements [6]. Conversely, the electrical properties have been explored through studies on transformer protection [7], mitigation strategies [8], and transformer modeling [9]. However, the AT has lower saturation flux density, iron loss and higher electrical resistance than the ST. These inherent differences significantly impact their performances under DC bias conditions. This paper analyzes the influencing factors of primary side currents in transformers under DC bias using analytical methods. DC bias experiments are conducted on AT and ST. The primary side currents under loaded and unloaded conditions are measured, and changes in harmonic amplitudes under DC bias are analyzed (Fig. 1). Reactive power variations among different transformers are also examined. Finally, finite element models (FEM) are implemented in ANSYS to compare differences in iron core losses under DC bias (Fig. 2). The results show the amplitude of the primary current in ST is 11.3% higher than in AT. The increase in harmonic amplitudes is more pronounced in ST compared to AT. Peak iron core losses in AT decrease by 85.4% compared to ST. DC bias exacerbates the disparity in iron core losses between AT and ST. Due to abstract length limitations, additional experimental and FEM results will be presented in the full paper.References: [1] Alexandrov N, Schulz R, Roberge R. Amorphous alloys for distribution transformers: design considerations and economic impact[J]. IEEE transactions on power delivery, 1987, 2(2): 420-424. [2] Harrison C W, Anderson P I. Characterization of grain-oriented electrical steels under high DC biased conditions[J]. IEEE Transactions on Magnetics, 2016, 52(5): 1-4. [3] Chen J, Wang D, Cheng S, et al. Influence of DC-biased magnetic induction on magnetic property of silicon steel[J]. IEEE Transactions on Magnetics, 2019, 55(5): 1-7. [4] Canturk S, Balci M E, Hocaoglu M H, et al. Investigation of the effects of DC bias on single-phase shell type transformers using frequency-dependent reluctance-based model[J]. IEEE Transactions on Magnetics, 2021, 57(9): 1-9. [5] Li Y, Zou J, Li Y, et al. Prediction of Core Loss in Transformer Laminated Core under DC Bias Based on Generalized Preisach Model[J]. IEEE Transactions on Magnetics, 2023. [6] Zhang Y, Wang J, Sun X, et al. Measurement and modeling of anisotropic magnetostriction characteristic of grain-oriented silicon steel sheet under DC bias[J]. IEEE transactions on magnetics, 2014, 50(2): 361-364. [7] Ahmadzadeh-Shooshtari B, Rezaei-Zare A. Advanced transformer differential protection under GIC conditions[J]. IEEE Transactions on Power Delivery, 2021, 37(3): 1433-1444. [8] Yang M, Deswal D, de Leon F. Mitigation of half-cycle saturation of adjacent transformers during HVDC monopolar operation—Part II: Detecting zero-sequence fault currents[J]. IEEE Transactions on Power Delivery, 2019, 35(1): 16-24. [9] Fuchs E F, You Y, Roesler D J. Modeling and simulation, and their validation of three-phase transformers with three legs under DC bias[J]. IEEE Transactions on Power Delivery, 1999, 14(2): 443-449.
Oriented silicon steel and Fe-based amorphous alloys are both widely used as iron core materials in power transformers. Silicon steel transformers (ST) offer good magnetic and electrical properties at a low cost. The amorphous transformer (AT) reduces 60% to 70% in no-load losses under sinusoidal excitation conditions compared to Si-steel core [1]. However, the performance of AT under DC bias remains less understood, despite the increasing occurrence of DC bias [2]. Existing literature primarily focuses on the magnetic and electrical properties of ST under DC bias [3]. Magnetic property research includes the frequency-dependent reluctance-based model [4], Preisach hysteresis modeling [5], and anisotropic magnetostriction measurements [6]. Conversely, the electrical properties have been explored through studies on transformer protection [7], mitigation strategies [8], and transformer modeling [9]. However, the AT has lower saturation flux density, iron loss and higher electrical resistance than the ST. These inherent differences significantly impact their performances under DC bias conditions. This paper analyzes the influencing factors of primary side currents in transformers under DC bias using analytical methods. DC bias experiments are conducted on AT and ST. The primary side currents under loaded and unloaded conditions are measured, and changes in harmonic amplitudes under DC bias are analyzed (Fig. 1). Reactive power variations among different transformers are also examined. Finally, finite element models (FEM) are implemented in ANSYS to compare differences in iron core losses under DC bias (Fig. 2). The results show the amplitude of the primary current in ST is 11.3% higher than in AT. The increase in harmonic amplitudes is more pronounced in ST compared to AT. Peak iron core losses in AT decrease by 85.4% compared to ST. DC bias exacerbates the disparity in iron core losses between AT and ST. Due to abstract length limitations, additional experimental and FEM results will be presented in the full paper.References: [1] Alexandrov N, Schulz R, Roberge R. Amorphous alloys for distribution transformers: design considerations and economic impact[J]. IEEE transactions on power delivery, 1987, 2(2): 420-424. [2] Harrison C W, Anderson P I. Characterization of grain-oriented electrical steels under high DC biased conditions[J]. IEEE Transactions on Magnetics, 2016, 52(5): 1-4. [3] Chen J, Wang D, Cheng S, et al. Influence of DC-biased magnetic induction on magnetic property of silicon steel[J]. IEEE Transactions on Magnetics, 2019, 55(5): 1-7. [4] Canturk S, Balci M E, Hocaoglu M H, et al. Investigation of the effects of DC bias on single-phase shell type transformers using frequency-dependent reluctance-based model[J]. IEEE Transactions on Magnetics, 2021, 57(9): 1-9. [5] Li Y, Zou J, Li Y, et al. Prediction of Core Loss in Transformer Laminated Core under DC Bias Based on Generalized Preisach Model[J]. IEEE Transactions on Magnetics, 2023. [6] Zhang Y, Wang J, Sun X, et al. Measurement and modeling of anisotropic magnetostriction characteristic of grain-oriented silicon steel sheet under DC bias[J]. IEEE transactions on magnetics, 2014, 50(2): 361-364. [7] Ahmadzadeh-Shooshtari B, Rezaei-Zare A. Advanced transformer differential protection under GIC conditions[J]. IEEE Transactions on Power Delivery, 2021, 37(3): 1433-1444. [8] Yang M, Deswal D, de Leon F. Mitigation of half-cycle saturation of adjacent transformers during HVDC monopolar operation—Part II: Detecting zero-sequence fault currents[J]. IEEE Transactions on Power Delivery, 2019, 35(1): 16-24. [9] Fuchs E F, You Y, Roesler D J. Modeling and simulation, and their validation of three-phase transformers with three legs under DC bias[J]. IEEE Transactions on Power Delivery, 1999, 14(2): 443-449.