| 摘要 |
PURPOSE:To always retain the terminal voltage of a self-excited induction motor constant by controlling the firing phase angle of a thyristor in a power converter in response to the magnitude of an error signal of the terminal voltage and a set voltage value. CONSTITUTION:A comparator amplifier 11 compares the terminal voltage of an induction motor 6 detected by a transformer 7 with the set voltage value of a voltage setting potentiometer 12 to detect and amplify the difference therebetween to produce an error signal to a phase controller 8. The controller 8 and a logic arithmetic firing circuit 9 control the thyristor firing phase angle of a power converter 4 in response to the magnitude of the error signal to alter the magnitude of reactive power. That is, when the load of the induction motor 6 is reduced to reduce the delayed reactive power, a capacitor 5 generates excessive lead reactive power to increase the exciting current to thereby increase the terminal voltage of the induction motor 6. Accordingly, the phase of the firing signal is controlled to flow large current at the reactor 3 to thereby reduce the lead reactive power by the capacitor. Thus, the terminal voltage of the induction motor can be always retained constant. |
