A new simultaneous gating GTO dual converter-fed DC motor drive without circulating current

A dual converter comprised of two three-phase AC-DC pulse width-modulated (PWM) gate-turn-off (GTO) thyristor converters is proposed. The gating pulse pattern of the converters is chosen so that no circulating current flows between the converters when they are operated simultaneously. A good input power factor is obtained with less ripple in the output current. A symmetrical type of gating is worked out in which all the GTOs in the converter are switched an equal number of times during each cycle of the source voltage. The motor current is free to reverse naturally at any moment, hence discontinuous conduction of the motor current can not occur. A four-quadrant closed-loop speed-controlled DC motor drive fed from the proposed dual converter has been designed, constructed, and tested. The experimental results obtained are shown to be in good agreement with theory.<>