Patent ID: 6469461
Filing Date: 2002-10-22
Classification: H02H,H02P

Abstract:
An apparatus for detecting a motor current flowing through delta-connected armature windings of a three-phase brushless dc motor when the motor is operated through a motor driver, comprising:a neutral voltage detecting circuit including three resistors which are connected at one end to the armature windings of the motor, respectively, and at the other end to a common junction, said neutral voltage detecting circuit measuring a voltage developed at the common junction as a neutral voltage V1 of the motor; a speed proportional voltage generator generating a voltage V2 proportional to a speed N of the motor according to an equation (1) below; and V2=AÂ·Nâ€ƒâ€ƒ(1) where A is a constant of proportion which is given by a relation of A =kÂ·&phgr;/2 where k is a constant of electromotive force and &phgr; is magnetic flux over one of the armature windingsa current determining circuit determining a voltage Vo according to an equation (2) below which indicates the motor current flowing through the motor Vo=VBâˆ’V1âˆ’V2â€ƒâ€ƒ(2) where VB is a voltage supplied to the motor driver to operate the motor.