Calculation Methods for the Self-inductance of Electromagnets with a Wide Air Gap

The objective of this study is the discussion of a simple calculation method for the magnetic reluctance and self-inductance of electromagnets with a wide air gap. Generally, the self-inductance of electromagnets with an air gap is calculated by the magnetic circuit theorem. However, it is difficult to calculate the reluctance of wide air-gaps because the magnetic flux spread cannot be ignored. In this study, the authors propose a simple calculation method for the magnetic reluctance of wide air gaps using the Nagaoka coefficient and investigate the self-inductance of electromagnets with a wide air gap using the magnetic circuit theorem. The proposed model was tested in comparison to the experimentally measured self-inductance of the test electromagnet. The results showed that the proposed calculation method can be used in the engineering design of electromagnets with a wide air gap.