High-quality electrical servo drives can only be designed and manufactured by using especially compatible and sophisticated components. A typical control actuator system is described consisting of a brushless synchronous motor and a transistor chopper inverter. Important aspects of the design and rating of a three-phase motor with rare-earth permanent magnets are pointed out. Several types of construction are described. The machine control system used is the familiar method of cascade control. By application of "space vectors" two special methods for fast response current control are developed. In the first case, inverter control signals are derived only from measured quantities. In the second case, the optimum controller output can be calculated if additional information about the controlled system exists. Finally, experimental results prove the excellent performance of this drive system.