| CPC H02P 29/20 (2016.02) [H02P 6/20 (2013.01); H02P 29/68 (2016.02)] | 19 Claims |

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1. A fan control system for controlling a fan motor that includes a rotor including blades, a stator, and an impregnated bearing impregnated with a lubricant and rotatably holds the rotor by the impregnated bearing,
the fan control system comprising:
a controller configured to select a control mode from a plurality of control modes including
a first mode to operate at a first rotation speed,
a second mode to operate at a second rotation speed lower than the first rotation speed, and
a third mode to operate at a third rotation speed higher than the second rotation speed and with a torque equal to or larger than a start torque that is a minimum torque necessary for starting the fan motor; and
a voltage conversion circuit for providing a first voltage to the fan motor in the first mode, a second voltage lower than the first voltage to the fan motor in the second mode and a third voltage higher than the second voltage to the fan motor in the third mode,
wherein the controller is configured to:
cause the voltage conversion circuit to provide the third voltage to the fan motor to start the fan motor,
after a predetermined time has passed, cause the voltage conversion circuit to switch the third voltage to the second voltage and provide the second voltage to the fan motor, and
after a predetermined condition is met, cause the voltage conversion circuit to switch the second voltage to the first voltage and provide the first voltage to the fan motor.
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