OPERATION SYSTEM OF THREE-PHASE WOUND-ROTOR INDUCTION MOTOR

PURPOSE:To maintain normal speed control and power control by passing predetermined zero-phase current even under one phase missing state thereby supplying three-phase balanced current and voltage to a rotor winding. CONSTITUTION:Upon a fault of a phase-c reversible converter 30c, switches 7a, 7e are opened while switches 7d, 7h are closed. Then cos(thetas+2pi/3) and sin(thetas+2pi/3) are inputted to multipliers 5a, 5b and multiplication of a current command id2* and cos(thetas+2pi/3) and that of iq2* and sin(thetas+2pi/3) are carried out. As for id2*.cos(thetas+2pi/3 the sign is inverted through a sign inverter 6 while operation of -id2*.cos(thetas+2pi/3)+iq2*.sin(thetaS+2pi/3) is carried out through an adder 1c. Thereafter, the difference between -id2*.cos(thetas+2pi/3)+iq2*.sin(thetaS +2pi/3) as a zero-phase current command and an actual i02 is operated in an adder 1d. Then the difference is added to respective phase outputs from a two- phase/three-phase converter 4 in adders 1e, 1f, 1g through a zero-phase current regulator 2c thus producing voltage commands for phases a, b and c.