Research on Three-Dimensional Stress Distribution of Reactor Core

Gapped iron-core reactors can obtain larger inductance, but they make larger vibration and noise than other kinds of reactors. On vibration dampers, many researchers kept their eyes on vibration isolation structures or vibration isolation materials. However, they did not compute reactor core vibration under fundamental frequency voltage or harmonic one. Because stress is the inherent reason of vibration and noise, this paper proposes a finite-element model for reactor core stress calculation based on the Maxwell stress theory. The model can handle reactor exciting currents, not only fundamental frequency but also superposition of fundamental frequency with different harmonics. Because core materials have different magnetic characteristics under different excitation conditions, this paper tested multigroup H-B curves to support the simulation. Then, the finite-element method is used to calculate the magnetic field and Maxwell stress distribution. Finally, the frequency spectrum of the stress is analyzed to provide a theory basis for further analysis of vibration and noise reduction in gapped iron-core reactors.

I. Introduction

In modern society, electrical energy is a kind of clean and convenient secondary energy. This kind of energy is widely used by people everywhere. Higher and higher quality electrical power supply is needed with the development of information technology. The development of smart power grids requires many kinds of electrical components to participate in. Reactors are important components in reactive power regulation of power system. Unlike transformers, reactors do not have secondary windings as demagnetizing coil, so reactor core is saturated easily. However, magnetic saturation of the gapped iron-core reactor is difficult to achieve because there are air gaps in it, and the gapped iron-core reactor has large inductance. Thus, this kind of reactors is widely used in many situations needing large inductance. Cores of gapped iron-core reactors are formed by stacking of core discs and marble. Marble is used as the insulator inserted in the gaps between the cores. In order to maintain the stability of the structure, core limb of the reactor is surrounded with an aluminum cylinder. Because of the alternating electromagnetic field, the periodical changed electromagnetic force is produced between the core discs. This electromagnetic force makes that gapped iron-core reactors have larger vibration and noise than other kinds of reactors.