Power factor improving apparatus for power converter

A power factor improving apparatus for power converter comprising:

• a transformer having a primary winding connected to an AC power supply and a plurality of secondary windings;
• a power converter having a plurality of controlled rectifying circuits, the AC sides of which are each connected to said respective secondary windings and the DC sides of which are connected in cascade with respect to a DC load;
• control means for phase-controlling a predetermined one of said plurality of controlled rectifying circuits and selectively fixing the other ones of the controlled rectifying circuits to either of the minimum and maximum output states;
• and
• capacitor banks for improving the power factor of said power converter;
• wherein means is provided for connecting said capacitor banks to the only one of said secondary windings to which a predetermined one of said controlled rectifying circuits is connected.

A power factor improving apparatus for power converter comprising:

• a transformer having a primary winding connected to an AC power supply and a plurality of secondary windings,
• a power converter having a plurality of controlled rectifying circuits, the AC sides of which are each connected to said secondary windings and the DC sides of which are connected in cascade with respect to a DC load;
• control means for phase-controlling said plurality of controlled rectifying circuits stage by stage then, after the output of a currently phase-controlled rectifying circuit has reached the maximum value, fixing this controlled rectifying circuit to that condition, and then phase-controlling the next controlled rectifying circuit;
• and
• capacitor banks for improving the power factor of said power converter;
• wherein means is provided for connecting said capacitor bank to only one of said secondary windings which is connected to a controlled rectifying circuit finally phase-controlled when the output of the power converter is increased by said control means.

A power factor improving apparatus for power converter comprising:

• a transformer having a primary winding connected to an AC power supply and a plurality of secondary windings;
• a plurality of power converters connected to the secondary windings of said transformer;
• and
• capacitor banks for improving the power factor of said power converters;
• each of said plurality of power converters comprising:
• a plurality of controlled rectifying circuits, the AC sides of which are each connected to said respective plural secondary windings and the DC sides of which are connected in cascade with respect to a DC load;
• and
• control means for phase-controlling only one of said plural controlled rectifying circuit so that two or more of said plural controlled rectifying circuits are never phase-controlled at the same time and for selectively fixing the other ones to either of the minimum and maximum output states;
• wherein means having a plural number of said capacitor banks corresponding to the number of said power converters is provided for connecting said capacitor banks to the secondary windings which are connected to said rectifying circuits in the power converters, respectively, and means for actuating only part of said plural number of connecting means when said power converters are at a relatively low output state.