The present disclosure proposes a resonant motor unit that has a resonant motor, a control unit for driving the resonant motor at a driving frequency, for short-circuiting the resonant motor during at least a first short-circuiting phase in successive driving cycles and for concluding the first short-circuiting phases by switching off the current flow through the resonant motor at least at a predetermined first time instant within the driving cycles, a measurement unit for successively measuring at least a first voltage signal provided by the resonant motor at the predetermined first time instant, and an evaluation unit for determining whether the first voltage signal has changed between successive measurements.
