Electromagnetic Shielding Analysis of a Canned Permanent Magnet Motor

The use of metallic cans in airgap forms an electromagnetic shielding phenomenon that characterizes a canned electrical motor. Imposed in alternating airgap flux field, cans induct strong and distributive eddy current, the fundamental feature that interacts original flux and determines output features. In particular that induction leads to additional can-shielding loss that is considerably much higher than traditional copper or iron losses. In this article, the can effect in terms of eddy current and loss is studied, based on a state-of-the-art permanent magnet motor. First, distribution characteristics of eddy induction and loss are analyzed via a combination method that each magnetic excitation is separately and then integrally taken. Then, the can loss by magnetic excitation, rotor speed, flux harmonics, as well as the change of traditional losses due to the use of cans, is analyzed. Measurement is taken as verification.