An electric machine, to a motor vehicle with such an electric machine, and to a method for operating such an electric machine. The electric machine includes at least one sliding contact which is formed by a slip ring connected to a rotor and by at least one brush and via which an operating current flows during an operation of the electric machine. A control unit is configured to control the operation of the electric machine. The control unit is configured to verify a predetermined operating criterion of the electric machine and, if said operating criterion is met, to inject a cleaning current according to a predetermined scheme, which then flows independently of the operating current via the sliding contact and cleans said sliding contact in order to maintain or improve a current transfer capability of the sliding contact.