| 摘要 |
PURPOSE:To prevent fluctuation of torque at the time of switching of control by storing the slip frequency at the time of slip frequency control and employing thus stored slip frequency, in place of a reference slip frequency, when transition is made to modulation factor control. CONSTITUTION:When control of slip frequency (fs) higher than about 5 km/h is carried out through a master controller 3, a current pattern IMP is operated 4 and then a slip frequency Fs, which varies based on the difference IMP-IM between the current pattern IMP and an actual IM, is operated and stored 5. Thus operated slip frequency FS is added to a rotor frequency RS determined at an operating section 2 to produce an inverter frequency command FINV which is then employed, together with outputs from an operating section 6 and a modulating section 7, for driving of a PWM modulating section 8. Upon speed decrease of an electric car, switches 9a, 9b are switched from (fs) side to Vc side and transition is made to variable voltage Vc control. Consequently, the difference IMP-IM is fed to the modulation factor operating section 7, output Fs from the operating section 5 returns on a signal line 10 to the operating section 5 and the final Fs stored therein is employed. By such arrangement, transition takes place smoothly from (fs) control to Vc control. |
