Patent ID: 6700400
Filing Date: 2004-03-02
Classification: B60L,H02P,Y02T

Abstract:
A constant detecting apparatus for a brushless DC motor for detecting an inductance of a brushless DC motor which includes a rotor provided with a permanent magnet and a multiphase stator which includes a plurality of stator wirings for generating a rotating magnetic field to cause rotation of the rotor, comprising:a phase voltage detecting device for detecting a phase angle and an effective value of a phase voltage of said brushless DC motor, a phase current detecting device for detecting a phase angle and an effective value of a phase current, a position detecting device for detecting a phase angle of an induced voltage from the magnetic pole position of said rotor, and a rotation number detecting device for detecting a number of rotations; a phase resistance value calculating device for calculating the phase resistance value and an induced voltage constant calculating device for calculating an induced voltage constant respectively based on the temperature of said brushless DC motor; a phase difference calculating device for calculating a voltage phase difference between the induced voltage and the phase voltage and a current phase difference between phases of the induced voltage and said phase current; a phase compensation value calculating device for calculating a phase compensation value which is used for compensating said voltage phase difference and said current phase difference based on said number of rotations; an iron loss calculating device for calculating an iron loss of said brushless DC motor; an effective phase current calculating device for calculating the effective phase current by subtracting the iron loss component from said phase current; and an inductance calculating device for calculating a magnetic field axis inductance and a torque axis inductance based on said phase resistance value, said number of rotations, said induced voltage constant, said voltage phase difference, said current phase difference, said phase compensating value, and said effective phase current.