Abstract
A new quasi-Coulomb relation between magnetic force vs distance, magnetic flux density, and magnetic pole area is proposed in this paper based on the empirical analysis on the magnetic force vs distance measurements. A simple device is designed and fabricated to measure the repulsive/attractive magnetic force between two magnets. The measurement results show that the relationship between the magnetic force and distance is similar to Coulomb’s electrostatic law, but the attraction is greater than the repulsion. The magnetic force is proportional to the integral of the magnetic flux density with the areas of the magnetic pole. This quasi-Coulomb relationship is useful to evaluate the torque and speed of a rim-driven motor, which plays an important role in electrified propulsion in green aviation technology.
Highlights
The rim-driven permanent magnet motor (RDM) consists of two rings connected by bearings
The outer ring is a stator made of an electromagnet controlled by commutating AC electric power, the inner ring is a rotor made of a permanent magnet, and the fan blade is attached with the inner rotor to generate thrust
(b) When the permanent magnet is about to pass over electromagnet 2, the Hall sensor detects the incoming magnet and control electromagnet 2 reverses the South Pole and North Pole, so that the permanent magnet continues to receive a repulsive force from electromagnet 2 and continues to move forward, in the meantime receiving the attraction from electromagnet 3
Summary
(b) When the permanent magnet is about to pass over electromagnet 2, the Hall sensor detects the incoming magnet and control electromagnet 2 reverses the South Pole and North Pole, so that the permanent magnet continues to receive a repulsive force from electromagnet 2 and continues to move forward, in the meantime receiving the attraction from electromagnet 3. In this way, the permanent magnet together with the inner ring will continuously keep moving forward under the dual repulsive and attractive force from outer ring electromagnets. Attractive Repulsive is the dragging force, which can be equivalent to the thrust. ∫OP Fdx represents the work done from the starting point O to point P
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