Magnetic levitation at low rotation frequencies using an on-axis magnetic field

Abstract

The Ucar effect is a simple yet astonishing phenomenon where a permanent magnet can be levitated by placing it in the vicinity of another permanent magnet that rotates sufficiently fast. The few previous works on this type of magnetic levitation all required magnets rotating on the order of 200 Hz. Here we investigate the influence of applying a static magnetic field on the rotation axis and show that this can lower the needed rotation frequency to below 50 Hz. We explain this by a detailed analysis of the force producing levitation, which is a superposition of a repelling force caused by the off-axis (rotating) magnetic field and an attractive force due to the on-axis field. We study this force and resulting levitation experimentally, analytically and numerically for three different rotor magnet configurations, showing that trends in the levitation distance and frequency range can be accurately predicted from both the numerical and analytical models.