| 摘要 |
PURPOSE:To prevent the occurrence of damage to a direct current motor, by obviating the failures of commutation at the thyristors of three phase thyristor bridge circuits, which are connected in reverse parallel, for driving the direct current motor by controlling a field magnet by direct current signals proportional to input line voltage. CONSTITUTION:A phase control circuit 23 controls thyristor bridge circuits 2A, 2B in response to deviation between speed command signals and speed feedback signals and deviation between said command signals and current feedback signals, and controls voltage supplied to an armature 4 of a direct current motor. An armature voltage detecting circuit 50 puts out negative signals when armature voltage Ea exceeds rates voltage Eo, and a phase control circuit 70 controls a thyristor bridge circuit 8 in response to a field magnet current set point proportional to alternating current input voltage Vac and deviation between field magnet currents and the output of the armature voltage detecting circuit 50, and controls field magnet currents.
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