Axial type flat PM motor with large air gap

An axial type flat permanent magnet motor (AFPM motor) is used for audio visual equipment, information actuators, etc. However it is limited to a small capacity with a small air gap. In this paper, the characteristics of the AFPM motor with a large air gap to protect and/or separate between the rotor and the stator for new applications are examined. The tested motor has an 8 mm air gap length and a 170 W output capacity. Maximum efficiency of the tested motor is about 80%, and if the air gap length is spread to 12 mm, the tested motor keeps 66% efficiency. Moreover, it is shown that the steady-state characteristics of the AFPM motor driven by a 6-step inverter can be estimated using d-q coordinates modeling.