Effects of conducting shields on the performance of pulsed rotating machines

Conducting shields are often used in pulsed rotating machines to protect the surrounding electronic devices and humans from exposure to high oscillating magnetic fields. These conducting shields are subjected to rotating magnetic fields due to excitation currents in rotor windings. This induces eddy currents, which reduce the magnitude of the operating component of magnetic fields (radial component in drum machine and axial component in disk machine), and thus reduce the mutual inductance between rotor and stator windings. The eddy currents also induce drag torques on the rotor windings, which results in a degradation of machine performance. In this paper, both disk and drum pulsed alternators are investigated by the finite element code EMAP3D. The effects of conducting shields on drag torques and the operating components of the magnetic field are studied, and the results are presented as functions of the gap between the rotor and the shield