Experimental Evaluation of Force-Current Characteristics of a Radial Electromagnetic Bearing

Radial electromagnetic bearings (EMBs) provide a friction-free and lubrication-free support to high-speed rotors. The electromagnetic force generated by a radial EMB is controlled through its excitation coil currents. The force-current characteristics are strongly influenced by numerous factors related to magnetic fields (eg., leakage, fringing, local saturation), core material properties, and geometry. This paper reports the prototyping of a radial EMB designed for a load capacity of 180 N; that can be produced without saturation of the magnetic core. An experimental setup is developed for static force-current characterization of the EMB at different values of airgap. While existing setups require a lathe or milling machine, the developed setup is simple and cost-effective. The force-current characteristics of the EMB prototype are measured and compared with the finite element-based results. The EMB prototype is able to deliver the desired load capacity of 180 N at the nominal airgap of 0.5 mm. The variation of measured force with coil current is mostly quadratic, indicating no magnetic saturation, except at high coil currents and low airgaps.