Comparison Of Active Magnetic Bearings With And Without Permanent Magnet Bias

A review of publications dealing with the design of active magnetic bearings reveals that some tend to a design with permanent magnets to create the bias flux, and others prefer a purely electric bias and control flux generation. The main scope of the paper is to compare both design principles, exemplarily for radial bearings. Interesting criterions are the negative stiffness, the coupling between the two radial force directions, the force/ volume ratio and the number and complexity of necessary parts.