A slip-ring unit for transmitting an electric current includes a first component group and a second component group arranged in a manner allowing rotation relative to each other. The slip-ring unit has a first track and a second track, a brush and a slip ring contacting each other over different rotational positions along one of the tracks. The first component group has a first connection terminal and an electric circuit for monitoring conditions, while the second component group has a second connection terminal The electric current is transmittable from the first connection terminal to the second connection terminal over the first track, and an electric voltage is transmittable over the second track to the circuit. The slip-ring unit is configured such that the first track and the second track are connected electrically.