Fans and pumps are widely used in industrial field. Huge power is consumed by them and much energy is wasted. The energy-saving method is to regulate their speed. If the speed adjustment technology is popularization, large benefits will be achieved.In this dissertation, many kinds of speed adjustable technology are analyzed and the situation of our country is considered. In these methods, two better speed drive technologies are cascade speed drive technology and high voltage vary frequency technology. So the two speed drive technologies will be deeply studied in the dissertation.In addition to the principle of cascade speed drive system and inner-feed motor basic framework are introduced. The engineering application of cascade speed drive system and control strategy and topology based on PWM converter are emphatically studied in novel cascade speed drive system. The main content and research results include:(1) Digital double closed-loop control strategy on boost chopper of cascade speed drive system is applied in the industrial field for the first time and large benefits have been achieved.. The reliability and dynamic performance of the equipment also can be improved.(2)The mathematical model of inner-feed chopper cascade speed drive system is presented by state space average method, the author design speed and current regulator according to engineering method based on the mathematical model. At the same time, it is found that the boost chopper of inner-feed cascade speed drive system is different from the conventional boost circuit. It is reverse process, its DC bus capacitance voltage is stabile, the motor speed will be changed by changing the occupation, the change relation between speed and occupation is linear.(3)If the SCR inverter is substituted with the PWM converter, it can not only improve power factor but also decrease harmonic. Inverter failure can be avoided, too. The power factor compensation principle is analyzed based on the instantaneous reactive power theory.