JPS5537838A - Terminal voltage controller for self-excited induction motor - Google Patents

Abstract

PURPOSE: To always retain the terminal voltage of a self-excited induction motor constant by absorbing the excessive lead reactive power by a capacitor by a reactive power control reactor connected in parallel therewith.

CONSTITUTION: Assuming that the AC line voltage and line current of a power converter 4 are represented by E, I, and thyristor firing phase angle by γ, delayed reactive power Win becomes Win=3^1/2.E.I×sin γ. Accordingly, if the terminal voltage of the induction motor 6 becomes larger than the set value of a voltage setting potentiometer 12, the value of the phase angle γ becomes larger in response to the difference therebetween, and the delayed reactive power further becomes larger. When the load of the motor 6 is reduced to produce excessive lead reactive power of the capacitor 5 to cause the terminal voltage of the motor to tend to raise, a comparator amplifier 14 detects it to thereby increase the phase angle γ by a phase control circuit 8 to increase the current flowing though a reactor 11 to thus absorb the excessive lead reactive power. Thus, it can retain the terminal voltage of the motor constant regardless of the variations of the load.

COPYRIGHT: (C)1980,JPO&Japio