I. Introduction
Homopolar hybrid active magnetic bearings (HH-AMB) make use of permanent magnet (PM) to generate a homopolar bias magnetic flux density [1]. This configuration allows for reducing both the Joule losses in the armature winding since it only supports the control current, and the iron losses in the rotor as the bias airgap magnetic flux density is mainly constant. These iron losses can be further decreased by removing the slots in which the winding is placed because this suppresses the local variations of the bias magnetic field due to the slot opening. Such slotless homopolar hybrid active magnetic bearing (SHH-AMB) has been studied in [2], based on a MEC model that was used to evaluate two characteristics of the SHH-AMB, namely the position stiffness and the current stiffness, with the aim of comparing them to slotted HHAMB. This MEC model directly accounts for the eccentricity of the rotor, necessary to evaluate the two stiffnesses, in the permeance function of the airgap. However, this MEC model neglects the leakage flux between the rotor and the PM, leading to a poor estimation of these two characteristics.