Mechanical strength of the rotor with internal permanent magnets

A magnetically excited synchronous machine is a potential candidate for use as a starter generator (STG) in gas turbine drives due to its inherent advantages such as high torque and power densities, good energy efficiency and controllability. This article discusses the design of a STG with an internal inductor, the permanent magnets of which are located inside the rotor core (IPM). However, with an increase in the diameter of the inductor, the centrifugal force acting on the permanent magnet (PM) and the pole piece increases strongly, which causes large deformations of the saturation bridges. The magnitude of mechanical stresses in the most loaded rotor elements is investigated by analytical and numerical methods. Variants of the inductor design are proposed, which reduce mechanical loads in the bridges while maintaining the PM volume. Dividing the PM in width into segments with the formation of central bridges made of soft magnetic material between them made it possible to balance the centrifugal force and reduce mechanical stresses to an acceptable level.