A new speed-control system suitable for a wound-rotor induction motor is introduced. This system is a combination of two schemes: primary voltage control by means of bias voltage control and Scherbius control. The performance characteristics of the system are obtained and compared for the two types of speed control (new speed control system against hybrid system and Scherbius system). The investigations are verified by the concurring data of theoretical and experimental results. The possibility exists for these systems to operate independently of each speed control over a wide range for the 3-phase wound-rotor induction motor, such as is sometimes used in pump driving systems. Both schemes have some inherent advantages and disadvantages. On balance, it appears that combined usage of the two systems is practical and convenient