Powdery particle conveying system and roots blower operating method

A powdery particle conveying system is provided in which electric power consumption can be saved when powdery particles are conveyed by use of a roots blower (2). In the case where the powdery particles are conveyed to a reservoir tank (A1-A4) near the roots blower (2), the frequency of a power source of a roots blower (2) driving motor (4) is reduced, thereby reducing an output of the roots blower (2). In contrast, in the case where the powdery particles are conveyed to a remote reservoir tank (B1,B2), a voltage of a commercial frequency is applied to the motor (4).