NON-TRANSFORMER FREQUENCY CONVERTER FOR CONTROLLED MEDIUM VOLTAGE ELECTRIC DRIVE Russian patent published in 2011 - IPC H02M5/452 H02M7/5387 H02M7/5395 H02M1/12 H02P27/08 H02J3/36 

FIELD: electricity.

SUBSTANCE: non-transformer frequency converter for controlled electric drive for networks with insulated neutral of class 6, 10 kV and more includes rectifier, three-phase voltage inverter with control unit of width modulation, capacitor connected to the direct current link of inverter, output LC filter, sensor of phase-to-phase voltages and control of phase-to-phase voltages, capacitor bank of LC filter, which is divided into two unequal parts. The main part (95% of total capacity or more) consists of capacitors connected between output phases of inverter and ungrounded. Small part is connected to output phases of inverter as per star circuit the neutral of which is grounded; to direct current link of inverter there connected are two magnetically connected windings arranged on common ferromagnetic core. Outputs of the above windings are connected so that when operating current of frequency converter flows via windings, magnetomotive forces of windings are opposite directed. To non-transformer frequency converter there introduced is voltage sensor of the above small part of capacitor bank of LC filter, damping neutral displacement control and adder, which are connected as it is specified in the request materials.

EFFECT: reducing the costs for current operational service, enlarging service life of converter, drive electric motor and supply main cables.

2 cl, 6 dwg