Novel Variable-Field Machine With a Three-Dimensional Magnetic Circuit

We propose a novel variable-field machine with toroidal windings to achieve both miniaturization and high efficiency. The proposed machine is characterized by a structure that uses three-dimensional (3-D) magnetic flux to increase the number of torque-generation faces. The 3-D structure prevents an increase in the machine volume due to the addition of variable-field coils. We investigated the principle of variable-field function using finite-element analysis and experimentation. We verified that the induced voltage and torque can be changed by regulating the direct current in the variable-field coil. Moreover, the field current revealed the effect of the no-load loss.