Abstract
Eddy currents are generated by the relative motion of a conducting plate and a magnet. Magnetic damper is a device that utilizes the magnetic drag force produced by the eddy current. The author call the magnetic damper moving parallel to the conducting disk the parallel-motion type magnetic damper. The author previously proposed the vector potential method for magnetic damper. The method has a good point that magnetic damping force can be calculated accuracy when a parallel-motion type magnetic damper is composed of rectangular magnets with alternating directional magnetic poles and a conducting plate. Generally ferromagnetic metal, for example a steel plate (S45C), has a property known as concentrating magnetic flux into itself. In this paper, using image method, we propose the new vector potential method for the magnetic damper with steel plates outside the rectangular magnets with alternating directional magnetic poles. The image method is a method for calculating a magnetic field by adding image currents in order to satisfy the boundary conditions between a magnetic material area and an air area in the magnetic field and the vector potential field. Damping ratios calculated by the new vector potential method are compared to the tests. As a result, analytical results are in good agreement with the experimental results.
