| 摘要 |
PURPOSE:To alleviate stress in a component by predicting demagnetization of rotor magnet from the ratio between r.p.m. of motor and output voltage thereof and making a decision that the magnet is damagnetized when the predicted value drops below a predetermined value thereby limiting maximum r.p.m. CONSTITUTION:A pattern determining section 11 determines a 120 deg. conduction pattern output corresponding to current operational mode. A speed operating section 12 determines a motor speed. A comparing section 13 compares a speed command fed from a speed command section 21 with an actual speed to produce an error which is employed in a PI control section 14 for determining a duty. A duty ratio with respect to an r.p.m. omega is then operated at a ratio calculating section 15 and demagnetization of rotor magnet is predicted if thus operated ratio is lower than a predetermined value. At that time, a life prolonging operation mode for limiting maximum r.p.m. takes place and a corresponding chopping signal is outputted for controlling an inverter circuit 2. When a decision is made that the rotor magnet is not demagnetized, a chopping signal is outputted in normal operation mode and the inverter circuit 2 can be controlled. |
