Analysis of the shading coil magnet

THE MAGNETIC FORCE of attraction on the armature of a shading coil magnet varies at double the frequency of the impressed voltage. A chattering noise begins when an externally applied force, tending to pull the armature away, increases to the point where it is about equal to the minimum value of the variable magnetic force. The main purpose of this paper is to develop a simple method of design that will make the minimum value of the variable magnetic force as large as possible, for a given magnet.