Patent ID: 8248013

Claim:
A plural fan system constructed by a plurality of fan devices, with each fan device comprising: a stator having a magnetizing member with a plurality of coils, and a driving unit electrically connecting with the coils; a rotor having a shaft with an end rotatably coupling to the stator, an impeller fixed to another end of the shaft, and an annular magnet mounted to an inner periphery of the impeller and facing the magnetizing member; and a speed control module having a control unit and a speed adjusting circuit, with the control unit providing a signal input port connecting to a pulse width modulation signal terminal, a signal output port connecting to the speed adjusting circuit, and a command output port connecting with the driving unit, with the speed adjusting circuit connecting between the signal output port and the pulse width modulation signal terminal, wherein the pulse width modulation signal terminal is for receiving a pulse width modulation signal, and the control unit sends a command signal to the driving unit and generates a state signal for the speed adjusting circuit to determine whether the pulse width modulation signal enters the control unit or not, with the signal output ports of the control units of the fan devices electrically connecting with each other, wherein, in which, upon entry into an abnormal state of any of the fan devices, the speed control module of each normally functioning fan device outputs an accelerating command signal to its driving unit, thereby setting the rotational speed of the remaining functional fan devices to a predetermined speed.