Importance

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Abstract

A brushless DC motor is disclosed. In the motor, an axial vibration limit unit is provided on a bearing and electromagnetically attracts a rotor, thus preventing the rotor from being centrifugally lifted during a high speed rotation of the rotor. In the operation of the motor, an axial displacement of the rotor is sensed by an induction coil of a sensor. The induction coil generates a variable induction current indicative of an axial displacement of the rotor, and outputs the current to a controller through an amplifier, thus controlling the vibration limit unit. The electromagnetic bearing of this invention thus supports the shaft and rotor in an axial direction and almost completely prevents any axial vibrations of the rotor, thereby reducing operational vibrations and noises and improving the axial dynamic characteristics of the brushless DC motor.

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First Claim