A Self-Closed Magnetic Circuit Based Power-Frequency Three-Phase Electromagnetic Heating System: Design and Performance Optimization

Authors:
  • YLYunhao Liang
    Yunhao Liang
  • QCQuanyou Cheng
    Quanyou Cheng
  • BSBaoye Song
    Baoye Song
  • HBHuakun Bi
    Huakun Bi
  • THTing Hao
    Ting Hao
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Abstract
Traditional electromagnetic heaters typically close the magnetic circuit through the connection of a core and yoke, which can lead to issues such as material redundancy and increased costs. This paper proposes a design concept centered on a self-closed magnetic circuit, eliminating the core and yoke structure while ensuring no increase in magnetic leakage and maintaining optimal system performance. Based on the structure of a three-phase three-column transformer, a 10kV/600kW coreless and yoke-less self-closed magnetic circuit three-phase spatial structure Dual-Pipe electromagnetic heater was designed. The heating efficiency reached 98.05%, demonstrating the effectiveness of the proposed structure. To address the issue of partial magnetic leakage at the junction between the inner pipe core and elbows, an inner pipe self-closed magnetic circuit structure was introduced. As a result, the heating efficiency increased to 98.26%, and the waveform distortion rate of the primary winding back electromotive force was reduced from 1.813% to 0.813%. The influence of key structural parameters, including the inner pipe hollow radius, the spacing between the three-phase closed pipelines, and the outer pipe wall thickness of the secondary winding, on performance is systematically studied and analyzed to identify the corresponding influence patterns. It was observed that as the hollow radius of the inner pipe increased, the heating power of the electromagnetic heater tended to stabilize. However, the waveform distortion rate of the primary winding back electromotive force increased accordingly. As the spacing between the closed pipes increased, the waveform distortion rate of the primary back electromotive force also increased, and the magnetic flux density decreased. It was observed that only at a certain distance would the magnetic field distribution become more uniform. As the wall thickness of the outer pipe increased, the maximum magnetic flux density in the inner pipe showed a decreasing trend. Based on the above observations, further optimization of the structural parameters was performed. Finally, a three-phase planar structure self-closed electromagnetic heater was designed, achieving a heating efficiency of 98.02%. Clearly, the three-phase spatial structure is capable of achieving higher efficiency. The design concept proposed in this paper, which centers on a self-closed magnetic circuit, effectively reduces magnetic leakage and minimizes the use of core materials. Powered by a power frequency source, it eliminates the need for high-frequency power electronic devices, thereby ensuring system reliability. This design is particularly suitable for medium- and small-sized, low-cost industrial and residential electromagnetic heating systems.

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