Multi-frequency converter speed-adjusting system for low-voltage high-power multi-branch AC motor

Abstract

The invention discloses a multi-inverter speed adjusting system of a low-voltage high-power multi-branch alternating current (AC) motor and pertains to the technical field of electrical engineering and relates to the electric transmission and the motor control of large machinery equipment. The system comprises a low-voltage high-power AC motor and at least two frequency converters, wherein, the low-voltage high-power multi-branch AC motor combines output ends of windings of a plurality of branches in parallel connection to form at least two three-phase output terminal groups each of which is connected with the frequency converters. Each three-phase output terminal group of the low-voltage high-power AC motor and the general low-voltage frequency converter connected with the motor form a separate circuit, thus avoiding the disadvantages of a driving system in which a high-voltage frequency converter supplies power to a high-voltage asynchronous motor. In addition, the general low-voltage frequency converter can adopt an SPWM control method with good output voltage waveforms and meanwhile, the price of the frequency converter is reduced and the reliability of the operation of the frequency converter is guaranteed.

Description

Technical field [0001] The invention belongs to the technical field of electrical engineering, relates to the electrical transmission and motor control of large-scale mechanical equipment, and is further said to be a multi-frequency converter speed regulation system of low-voltage high-power AC motors. Background technique [0002] Medium and large AC motors, such as high-voltage asynchronous motors, are mainly used as the main drive motors for mechanical equipment in mining, petroleum, chemical, power, and water supply and drainage systems. In order to reduce the current, voltage levels above 1kV are usually used. This voltage level not only brings many problems to the design, manufacturing and maintenance of the motor, but more importantly, for the transmission system that requires variable speed and energy saving, the corresponding high-voltage inverter is very expensive. Compared with the low-voltage inverter, the price per kilowatt is about It is about 2.5:1. Moreover, its...

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Problems solved by technology

Patent No.: 03126473.5, the name is an improved high-voltage high-power inverter. There is a buffer circuit connected in series between the primary side of the multi-side winding rectifier transformer and the high-voltage switch of the grid. The above buffer circuit limits the charging current and reduces the power-on impact of the grid on the inverter, but essentially does not change the original shortcomings of the high-voltage inverter

Patent No.: 200610169615.2, the name is a medium-power low-voltage inverter based on insulated gate bipolar transistors. Although it has a compact structure, high power density, easy installation, and the stray inductance between lines is small, its own cooling problem is still difficult. solve

To a certain extent, the performance of the inverter has been improved, but it is fundamentally unable to solve the problems that the cost performance, reliability and performance of the high-voltage inverter are not as good as those of the low-voltage inverter, as well as the problem of the limit current of the low-voltage high-power inverter and its own cooling problems. Broad application is limited

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