Pekko Jaatinen

Design of a bearingless 100 kW electric motor for high-speed applications

In this work a design optimization of the high-speed buried-type interior permanent magnet bearingless motor with significant power for such machines is presented. The geometry, windings arrangement and magnets are adjusted from the non-levitated motor design to avoid the significant magnetic saturation and achieve the performance target without oversizing the machine. The analytical design is optimized in finite element method analysis. The effect of stator skew on machine performance is thoroughly investigated.

Optimization of the rotor geometry of a high-speed interior permanent magnet bearingless motor with segmented magnets

Bearingless motors combine the torque generation of electrical motors and the radial suspension force capabilities of traditional magnetic bearings. The magnetomotive force (MMF) distribution in the motor generates radial force interference. The interference force affects the angle between the actual and desired radial force. This angle is called the force error angle. For stable levitation of the rotor of the bearingless motor the force error angle must be minimized in the design phase of the machine. This paper presents an optimal rotor structure for minimization of the error angle in a high-speed interior permanent magnet bearingless motor with magnets embedded in the rotor surface.

Laboratory testing of an active magnetic bearing supported permanent magnet 3.5 kW blower prototype

A commissioning and laboratory tests of an active magnetic bearing supported PM 3kW blower are presented. The motor operation is evaluated in no-load and load tests. An identification of AMB-rotor system, testing of H∞ centralized control and mass-flow of the blower for recirculation of anode gas in a SOFC are discussed. The key results include comparison between analytical and measured values of an output sensitivity function of different MIMO controllers, measured efficiency and output motor power, and blower measurements.

Design of 6-slot inset PM bearingless motor for high-speed and higher than 100kW applications

This paper presents design optimization of high-speed and high-power bearingless motor/generator. Because of absence of separate suspension windings, in addition to the motor windings, and tooth coil arrangement a compact and axially short actuator can be achieved. A surface PM and inset PM rotor geometries are compared. The twin bearingless solution with separate axial active magnetic bearing delivers 6 degrees of freedom self-bearing motor system suitable for pumps, compressors and blower applications with considerable loads and precise clearance control in every direction. Both torque and suspension radial forces are induced with superimposed bearing and motor currents. Optimal design in terms of motor and suspension performances is investigated using finite element method and time stepping simulations.

Improving of bearingless 6-slot IPM motor radial force characteristics using rotor skew

Bearingless machine technology is well-suited for high-speed applications as it removes the mechanical friction by supporting the rotor with electromagnetic force. For electrical machine, which is operating in high-speed region, a short rotor length is beneficial to avoid the rotor vibration caused by structural properties of long rotor. A 6-slot tooth-coil wound bearingless machine is well suited for high-speed applications as it shortens the rotor length compared to more traditional distributed winding configuration. Drawback of the tooth-coil wound machine is the higher space harmonic content which decrease the radial force performance characteristics including ripple and disturbance forces. In this paper, the rotor skew is introduced to improve the radial force characteristics of IPM bearingless machine.

Modelling and evaluation of radial-axial PCB capacitive position sensor prototype

This work presents the compact radial-axial 3D PCB capacitive position sensor. The FEM model, numerical analysis and prototype verification are presented. The capacitances of circuit are estimated using 3D model and are verified based on spectral analysis. The open and closed-loop measurements prove feasibility in applications related to rotating machinery.

Implementation of a flux-based controller for active magnetic bearing system

The traditional control method for active magnetic bearings uses a bias current to linearize control at the operation point. In this paper a flux-based controller with the zero bias current for radial magnetic bearings is presented. The controller is implemented in FPGA and functionality is verified with the co-simulation.