1.磁浮技术与磁浮列车教育部重点实验室 西南交通大学电气工程学院 成都 611756; 2.西南交通大学电气工程学院 成都 611756; 3.GeePs-CNRS Laboratory Centrale Supélec University of Paris-Saclay Gif-sur-Yvette 91192 法国;
Equivalent Circuit Modeling and Experimental Study on Current Output Characteristics of High-Temperature Superconducting Transformers for Flux Pumps
Gong Tianyong1,2,3, Loïc Quéval3, Ma Guangtong1,2
1.Key Laboratory of Magnetic Suspension Technology and Maglev Vehicle School of Electrical Engineering Southwest Jiaotong University Chengdu 611756 China; 2. School of Electrical Engineering Southwest Jiaotong University Chengdu 611756 China; 3. GeePs-CNRS Laboratory Centrale Supélec University of Paris-Saclay Gif-sur-Yvette 91192 France;
Abstract：As a low-voltage, high-current DC power supply device, the superconducting flux pump charges superconducting loads through contactless power transfer, offering significant advantages such as compact structure, low heat leakage, and high output current. It holds important application value in fields like magnetic resonance imaging (MRI), high-field magnet facilities, superconducting magnetic energy storage, and superconducting maglev. The transformer-rectifier type flux pump utilizes a superconducting switch to rectify the transformer’s AC current into DC, featuring benefits such as high charging voltage and flexible control over the charging process. Within a transformer-rectifier flux pump, the superconducting transformer plays a critical role. In typical designs, to achieve a high current amplification ratio, the primary winding turns are usually increased while the secondary winding is correspondingly reduced to a single-turn structure. This configuration leads to a significantly large primary self-inductance and an extremely small secondary self-inductance. Simultaneously, due to the very low resistance of the superconducting secondary, the reactive component dominates the secondary impedance, making the transformer current highly sensitive to changes in secondary inductance. Accurately obtaining the inductance parameters thus becomes key to precisely calculating the transformer’s current output and the flux pump’s charging performance. However, existing methods typically calculate parameters like transformer reluctance or inductance based on theoretical formulas, which struggle to accurately characterize the nonlinear permeability of the core and leakage flux effects, limiting computational accuracy. Furthermore, the circuit models commonly employed are mostly based on solving transient differential equations, leading to low computational efficiency when simulating the slow charging of large inductive loads, which hampers the timeliness of system optimization design. To address the aforementioned issues, this paper focuses on the current output characteristics of high-temperature superconducting (HTS) transformers used in flux pumps. Firstly, the transformer’s inductance parameters are determined experimentally, its equivalent circuit model is established, and its short-circuit characteristics are analyzed. Building upon this, an equivalent circuit model for the flux pump system is further constructed, and an HTS transformer with high output current capability is designed. Subsequently, the charging performance of the flux pump system for a superconducting electrodynamic suspension (EDS) magnet is investigated. The main conclusions are as follows: (1) Transformer short-circuit experiments show that as the primary voltage U1 increases, the short-circuit current variation can be divided into four stages: linear increase, nonlinear increase, nonlinear decrease, and sudden drop. These nonlinear changes originate from the increase in the resistance of the superconducting secondary winding. (2) Regarding the two equivalent circuit models of the transformer: the frequency-domain model can effectively predict the linear increase stage of the short-circuit current (when the peak secondary current is below its critical current); the time-domain model can accurately predict both the linear and nonlinear increase stages of the short-circuit current (when the peak secondary current exceeds its critical current but does not cause significant temperature rise). (3) By introducing the load charging curve equation into the frequency-domain model, the proposed model can quickly and fairly accurately reproduce the charging process of the flux pump. Compared with the time-domain model, its maximum relative error is 7.4%, but the computational efficiency is improved by three orders of magnitude, providing an efficient computational tool for transformer optimization design and flux pump charging performance analysis. (4) To improve the current output capability of the HTS transformer, a superconducting transformer based on a parallel secondary structure was designed. The flux pump system using this transformer can excite an HTS EDS magnet to its rated current of 250 A, but the required excitation time is as long as 30 hours, necessitating further optimization to shorten the excitation time.
龚天勇, Loïc Quéval, 马光同. 磁通泵用高温超导变压器电流输出特性的等效电路建模与实验研究[J]. 电工技术学报, 2026, 41(13): 4515-4526.
Gong Tianyong, Loïc Quéval, Ma Guangtong. Equivalent Circuit Modeling and Experimental Study on Current Output Characteristics of High-Temperature Superconducting Transformers for Flux Pumps. Transactions of China Electrotechnical Society, 2026, 41(13): 4515-4526.
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2026, Vol. 41 
