PURPOSE: To enable direct current to be always controlled stably and preferably by automatically adjusting a control element according to the inductance fluctuation of a DC reactor in a main circuit, regarding an elevator equipped with a current inverter as the main circuit.
CONSTITUTION: Three-phase full wave direct current converted via a converter 1 is again converted to three-phase alternate current via an inverter 2 in an elevator current control system, and an induction motor 4 is driven using the three-phase alternate current. A capacitor 8 capable of changing capacitance in such a way as corresponding to an applied voltage value (e.g. junction capacitance of semiconductor) is used as the control element of the elevator current control system. Also, a constant control microcomputer 10 refers to a data table on the basis of the feedback voltage of direct current, and generates a capacitance instruction voltage for the capacitor 8. Then, a proportional integration circuit 11 integrates a deviation between a current instruction and direct current feedback, and this integrated value is amplified with an amplification circuit 12 to generate a control signal for controlling the converter 1.
MEGURO TOSHIO
ANDO TAKEYOSHI
HITACHI BUILDING SYST ENG
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