The purpose of this paper is to present an experimental method to separate losses components due to the rotation of the rotor in very-high-speed permanent magnet machines with ball bearings. In addition, it presents and validates an analytical model for the computation of induced eddy current losses in rectangular section conductors due to a rotating magnetic field. It also validates an empirical windage losses model. The measurements are performed on a very-high-speed miniaturized permanent magnet motor up to 400 krpm. To the authors’ knowledge it is one of the smallest and fastest electrical motor ever operated.