Patent ID: 7340791

Claim:
A washing machine, comprising: a rotary tub; a motor linked to the rotary tub to be supplied with drive power and rotating to rotate the rotary tub; a vibration detector to detect a vibration level of the rotary tub during a rotation of the rotary tub using a variation of the drive power supplied to the motor when the motor rotates; and a controller to control a current rotational speed of the motor to be increased, maintained or decreased according to the vibration level of the rotary tub detected by the vibration detector, to attenuate the vibration level of the rotary tub, wherein the variation of the drive power supplied to the motor corresponds to a plurality of different reference ranges which determine the vibration level of the rotary tub, and wherein the plurality of different reference ranges include: a first reference range representing when a rotating state of the rotary tub is stable; a second reference range representing when the rotating state of the rotary tub is desirable; and a third reference range representing when the rotating state of the rotary tub is unstable.