US 7,531,982 B2
Motor drive apparatus capable of accurately estimating demagnetization of permanent magnet motor
Masaki Okamura, Toyota (Japan); and Takashi Yamashita, Nagoya (Japan)
Assigned to Toyota Jidosha Kabushiki Kaisha, Toyota (Japan)
Appl. No. 10/559,932
PCT Filed Jul. 08, 2004, PCT No. PCT/JP2004/010091
§ 371(c)(1), (2), (4) Date Dec. 08, 2005,
PCT Pub. No. WO2005/025047, PCT Pub. Date Mar. 17, 2005.
Claims priority of application No. 2003-204733 (JP), filed on Jul. 31, 2003.
Prior Publication US 2006/0119312 A1, Jun. 08, 2006
Int. Cl. H02P 27/00 (2006.01)
U.S. Cl. 318—701  [318/807; 318/700; 318/432] 10 Claims
OG exemplary drawing
 
1. A motor drive apparatus comprising:
a permanent magnet motor; and
a controller that:
estimates an amount of demagnetization of the permanent magnet motor based on a voltage control amount of a q axis applied under control of the permanent magnet motor using a d-q axis transformation; and
limits an output of the permanent magnet motor when the estimated amount of demagnetization is larger than a predetermined value, wherein
the controller (i) obtains a reference value that is the voltage control amount of only the q axis among the respective voltage control amount of the q axis and a d axis in a case where the permanent magnet motor is not demagnetized, according to a current and a motor revolution number of the permanent magnet motor being controlled, and (ii) estimates the amount of demagnetization based on a comparison between the reference value and an actual value under the control of the voltage control amount of only the q axis among the respective voltage control amount of the q axis and the d axis.