Electric rotary machine having a slip-ring arrangement , having a rotor , a sliding-contact device which is arranged on the rotor and has a slip ring and a sliding-contact element with which the slip ring can make electrical contact, a radial impeller wheel which is arranged on the rotor and has an intake device, wherein the intake device is embodied in such a way that during the operation of the radial impeller wheel a cooling fluid, which can be expelled, can be drawn into the radial impeller wheel by the intake device along the sliding-contact device , and a spiral housing which is of spiral design and surrounds a radial circumference of the radial impeller wheel , wherein the spiral housing has a spiral region and an outflow region which is arranged downstream of the spiral region and has an outflow opening , wherein in the spiral region an inner wall of the spiral housing is spaced apart from a rotational axis of the rotor in a way corresponding essentially to a spiral function, wherein in a junction region between the spiral region and the outflow region a tongue is formed by the inner wall in such a way that on the tongue , in a sectional plane perpendicular to the rotational axis, there is a tongue gap between the inner wall and an outer circumference of the radial impeller wheel , which tongue gap is the minimum distance between the inner wall and the outer circumference of the radial impeller wheel , wherein in the spiral region a maximum value of a distance between the outer circumference of the radial impeller wheel and the inner wall, said distance being measured proceeding radially from the rotational axis of the rotor , corresponds to six times to eight times the tongue gap , characterized in that the tongue is dull angled. having a rotor , a sliding-contact device which is arranged on the rotor and has a slip ring and a sliding-contact element with which the slip ring can make electrical contact, a radial impeller wheel which is arranged on the rotor and has an intake device, wherein the intake device is embodied in such a way that during the operation of the radial impeller wheel a cooling fluid, which can be expelled, can be drawn into the radial impeller wheel by the intake device along the sliding-contact device , and a spiral housing which is of spiral design and surrounds a radial circumference of the radial impeller wheel , wherein the spiral housing has a spiral region and an outflow region which is arranged downstream of the spiral region and has an outflow opening , wherein in the spiral region an inner wall of the spiral housing is spaced apart from a rotational axis of the rotor in a way corresponding essentially to a spiral function, wherein in a junction region between the spiral region and the outflow region a tongue is formed by the inner wall in such a way that on the tongue , in a sectional plane perpendicular to the rotational axis, there is a tongue gap between the inner wall and an outer circumference of the radial impeller wheel , which tongue gap is the minimum distance between the inner wall and the outer circumference of the radial impeller wheel , wherein in the spiral region a maximum value of a distance between the outer circumference of the radial impeller wheel and the inner wall, said distance being measured proceeding radially from the rotational axis of the rotor , corresponds to six times to eight times the tongue gap , characterized in that the tongue is dull angled. <EOS>