End region three-dimensional magnetic flux calculation and error influence on small slenderness ratio AC exciter

Traditional state-space equation method can not accurately calculate transient inductances considering of magnetic field saturation and leakage, while two-dimensional finite element method (FEM) is not applicable for small slenderness ratio AC exciter in aeronautic power. Therefore, one end region three-dimension magnetic flux calculation method is proposed. With arbitrary six-node pentahedron structure in local coordinate, three-dimension end region magnetic flux equation is deduced to calculate end armature inductance. Simulations on a certain AC exciter fully prove magnetic leakage can not be ignored if slenderness ratio is below than 0.3. Moreover, it proves that the method is more precise than state-space equation and direct two-dimensional FEM and less time-consuming than direct three-dimension FEM, so it gives good reference for transient inductances analysis especially for smaller slenderness ratio synchronous generator.