In this paper a measurement technique for synchronous machines is presented that allows the experimental identification of stator flux linkage as well as iron and friction losses in each operation point. The technique can be applied to all kinds of synchronous electric machines, even to machines showing magnetic anisotropy, iron saturation and cross-coupling. Influences of spatial harmonics, inverter switching and temperature transients are considered. The method uses steady-state measurements at constant motor speed. It is based on a combined evaluation of two operation points with corresponding magnetic states, one being in the motor and the other in the generator mode. The method is demonstrated by characterization of an automotive permanent magnet synchronous traction motor.