A rotor driven by an ideal source, i.e., a source capable of delivering unlimited amount of power, becomes unstable beyond a certain threshold spin speed due to non-conservative circulatory forces. The circulatory forces considered in this paper arise out of rotating internal damping. If the drive is non-ideal then the rotor spin speed cannot exceed the stability threshold. This phenomenon is a type of the Sommerfeld effect. In this work, a DC motor driving four-degrees-of-freedom rotor with internal damping and gyroscopic effects is considered and the corresponding steady-state spin frequency and the whirl orbit amplitude are analytically derived as functions of the parameters of the drive and the rotor system.