  Future developments of lighter, more compact and powerful motors-driven by
environmental and sustainability considerations in the transportation
industry-involve higher stresses, currents and electromagnetic fields. Strong
couplings between mechanical, thermal and electromagnetic effects will
consequently arise and a consistent multiphysics modeling approach is required
for the motors' design. Typical simulations-the bulk of which are presented in
the electrical engineering literature-involve a stepwise process, where the
resolution of Maxwell's equations provides the Lorentz and magnetic forces
which are subsequently used as the external body forces for the resolution of
Newton's equations of motion. The work presented here proposes a multiphysics
setting for the boundary value problem of electric motors. Using the direct
approach of continuum mechanics, a general framework that couples the
electromagnetic , thermal and mechanical fields is derived using the basic
principles of thermodynamics. Particular attention is paid to the derivation of
the coupled constitutive equations for isotropic materials under small strain
but arbitrary magnetization. As a first application, the theory is employed for
the analytical mod-eling of an idealized asynchronous motor for which we
calculate the electric current, magnetic, stress and temperature fields as a
function of the applied current and slip parameter. The different components of
the stress tensor and body force vector are compared to their purely mechanical
counterparts due to inertia, quantifying the significant influence of
electromagnetic phenomena.
