a control system is disclosed for a cascade control of a dynamic compressor having a variable speed of rotation to maintain a constant pressure to a process . the method consists of a successive junction of control loops for controlling the speed of rotation , the flow rate of a compressor , the pressure in the delivery or in suction ; the output signal of each outer loop being the input signal for the inner loop and each of the loops containing a compensating element to reduce the effects of large time constants of all inner loops . an automatic control system based on using the above method , distinguished by its great transient and steady state precision in maintaining a main controlled parameter , and by the high reliability of protection of the compressor from surge and from a dangerous increase of the speed of rotation .