Hitachi, Ltd.

Katsuaki Suzuki

Kiyoshi Nakamura

Kiyoshi Nakata

Tokunosuke Tanamachi

Yoshio Tsutsui

Wataru Miyake

Hisakatsu Kiwaki

Kyozo Tachibana

Tatsuo Horie

Yoshimitsu Onoda

Shozuchi Miura

An electric railway vehicle control system including a converter for converting a single-phase a.c. voltage to a d.c. voltage, a PWM inverter for inverting the d.c. output of the converter to a variable voltage, variable frequency a.c. voltage, and a three-phase induction motor supplied with the a.c. output voltage of the inverter to drive electric railway vehicles. The control system further includes a unit for controlling the output voltage of the inverter in a variable voltage, variable frequency mode for changing the output voltage substantially relative to a change in the output frequency thereof and in a constant voltage, variable frequency control mode for fixing the output voltage to a substantially constant value, and a unit for detecting a rectification ripple in a frequency band including a frequency double the frequency of the single-phase a.c. voltage included in the d.c. input voltage to the inverter.

Inverter control apparatus

In an inverter control apparatus including a pulse width modulation inverter supplied with power from a d.c. power source to generate an a.c. output, a frequency control unit controlling the output frequency of the inverter, and a voltage control unit controlling the output voltage of the inverter, a frequency adjusting unit is provided to adjust the operating frequency of the inverter so that the product of voltage and time in each positive half cycle of the output voltage of the inverter becomes equal to that in the next adjacent negative half cycle of the output voltage of the inverter. When the inverter is used in an apparatus for controlling an induction motor, the frequency adjusting unit adjusts the output frequency of the inverter according to the result of detection of a ripple factor of an input voltage of the inverter, and a frequency adjusting-factor correcting unit corrects the frequency adjusting factor of the frequency adjusting unit according to at least one of the output of an induction-motor rotation frequency detector and the output of the voltage control unit.

The two secondary windings of a transformer the primary winding of which is connected to an AC power supply are each provided with a controlled rectifying circuit. The DC sides of the rectifying circuits are connected in series to supply power to DC motors. One of the secondary windings is detachably connected with a capacitor bank. The capacity of the capacitor bank is selected so that the power factor of the converter can be improved to a satisfactory value when the two rectifying circuits are both controlled to produce output voltages. The capacitor bank becomes connected in response to the fact that the current in the primary winding of a transformer has arrived at a predetermined value.

Power factor improving apparatus for power converter

Growing community of inventors

Kitaibaraki, Japan

Katsuaki Suzuki