Patent ID: 7174731

Claim:
A rotational speed control system, comprising: at least one or more motor drive chains each comprising: rotational speed instructing means outputting a rotational speed instructing signal setting a motor rotational speed; a first motor driver receiving said rotational speed instructing signal from said rotational speed instructing means and driving a motor corresponding to itself based on said rotational speed instructing signal; and at least one second motor driver capable of communicating with said first motor driver in a digital value, receiving said rotational speed instructing signal from said first motor driver and driving a motor corresponding to itself based on said rotational speed instructing signal, and central monitoring means monitoring the operations of said first and second motor drivers in units of said motor drive chains by communicating with said first motor driver of each of said motor drive chains, wherein said motor drive chains include a plurality of motor drive chains, and said first motor driver of each of said plurality of motor drive chains interrupts communication with said central monitoring means when an abnormal condition occurs in the motor drive chain to which it belongs.