a drive control means 12 which specifies drive order and timing in accordance with a priority ranking for the machines and a drive instruction producing means 13 which sends drive instructions to the machines which are to be actuated the drive control means 12 delays the timing of start of actuation for the machine having lower priority when the voltage drop exceeds the predetermined allowable value next the operation will be described with reference to the flowchart of fig2 first the notices of actuation that are produced by the actuation notice producing devices 6a to 6c a predetermined period of time beforehand are received step s21 the total amount of voltage drops in the machines to which the notices have already been issued is calculated and the judgement means 11 operate to judge whether or not the total amount thereof that is the voltage drop in the power source is within the predetermined allowable range step s22 if it is within the range the drive control means 12 and the drive instruction producing means 13 sets the actuation timing for the machines and give permission to actuate them step 23 if the total amount of the voltage drop exceeds the predetermined allowable value the start timing of actuation of the machines having lower priorities that are relatively low in working are selectively delayed by the drive control means 12 so as to bring the total amount of the voltage drops to be.