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| Method to Measure and Weaken the Residual Flux of the Power Transformer Core |
| Ge Wenqi,Wang Youhua,Chen Xueguang,Xiao Shuxin,Yang Xiaoguang,lü Dianli |
1. School of Mechanical Engineering Hebei University of Technology Tianjin 300130 China;
2. Province-Ministry Joint Key Laboratory of Electromagnetic Field and Electrical Apparatus Reliability Tianjin 300130 China |
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Abstract When the power transformer is de-energized, there will be a certain amount of residual magnetic flux due to the inherent hysteresis in the ferromagnetic material and the closed structure of the transformer core. The residual flux may increase saturation of the iron core and lead to high transient magnetizing inrush current. This paper presents a novel method to measure the residual flux. Starting from analyzing the principle of residual magnetic flux, the transient electromagnetic simulation for the power transformer is analyzed and a formula of the residual magnetic flux and the current is established based on the results. A toroidal transformer iron core has been selected. Through analyzing the transient measurement current signals observed from the oscilloscope, the analyzed signals were substituted into the relational formula obtained by simulation. The DC (direct current) current method were identified, through a literature review to weaken the residual flux and set the demagnetization current according to the obtained residual flux. The comparison of the measurement current waveforms before and after demagnetization shows that this method can effectively weaken the residual flux and achieve the goal of weakening the inrush current, which finally proves the effectiveness of the demagnetizing method.
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Received: 21 November 2013
Published: 14 September 2015
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2015, Vol. 30 
