Thermal analysis of high-speed permanent magnet motor with cooling flows supported on gas foil bearings: part II - bearing modeling and case studies

This paper presents the modeling of mechanical loss in Gas foil bearings (GFBs) that support a Permanent magnet (PM) motor. This paper also presents parametric studies to evaluate the effects of carrier harmonics in the input current and cooling-air supply on the motor thermal performance. Because GFB functions not only as a heat source but also as a thermal resistance, we model it as an equivalent element comprising a thermal conductor. The calculation of the bearing loss from the hydrodynamic analysis shows one-order-ofmagnitude smaller values than the electromagnetic losses, thus indicating a slight effect on the PM motor performance. A case study shows the strong effects of the carrier harmonics and cooling-air supply on the motor thermal performance at a rotor speed of 35 krpm. A further study at an increased speed of 60 krpm shows significant increases in the motor losses and temperatures.