Noise Reduction of a Three-Phase Reactor by Optimization of Gaps Between Cores Considering Electromagnetism and Magnetostriction

To reduce the noise of a reactor connected to an inverter power supply, we have already proposed an improved one-phase reactor, in which the hard materials are chosen as the insulators inserted in the gaps between the cores, and gaps are added in the yokes, using a three-dimensional (3-D) coupled magnetic field and vibration analyses taking account of both the electromagnetism and magnetostriction. The effectiveness was shown by experiment. In this paper, the design method is improved and applied to a three-phase reactor. First, the method of determining the optimal hardness of insulators inserted in gaps, so that both the displacements by electromagnetism and magnetostriction are canceled with each other, is proposed. In this method, the optimal hardness of gaps can be represented using a simple equation involving the lengths of the iron cores and the gaps, and a parameter concerned with magnetostriction. Moreover, the method of adding gaps in the yokes without changing the balance and reluctance of a three-phase reactor is also proposed. It is shown that the displacements of the reactor improved by using the proposed methods can be reduced to be 1/25 of the ordinary reactor in the 3-D coupled magnetic field and mechanical analyses taking account of both the electromagnetism and magnetostriction and laminated structure of the iron cores.