Fully laminated shell-type three-phase rotating transformer for brushless applications

A fully laminated shell-type three-phase rotating transformer, appropriate for the most brushless applications, is proposed. The stationary and rotary parts of the proposed machine include both radially and axially laminated magnetic cores. Thanks to the special construction, the mechanical assembling of the proposed device in an integrated three-phase unit is very simple. In addition, a high permeance, low eddy current magnetic path is provided for the magnetic flux in the machine volume. However, to limit the core eddy currents in a normal range, a special geometry is selected for the radially laminated parts. Using the transformer magnetic equivalent circuit, the self and mutual inductances are obtained analytically. Based on the developed analytical model, geometrical dimensions are selected such that, a balanced three-phase machine is provided. Finally, finite-element analysis and experimental results are used to verify the obtained analytical model.