Inverter power sources utilize thyristor circuits to convert direct current (DC) into alternating current (AC), which is the reverse process of rectification and is defined as inversion. For instance, in electric locomotives equipped with thyristors, when descending a hill, the DC motor operates as a generator to brake, converting the locomotive's potential energy into electrical energy, which is then returned to the AC power grid. Similarly, a running DC motor can be made to quickly brake by operating it as a generator, transforming the motor's kinetic energy into electrical energy and returning it to the power grid.
The Principle of Inverter Power Supply: A circuit that converts direct current (DC) into alternating current (AC) is called an inverter circuit. In certain situations, the same thyristor conversion circuit can function as both a rectifier and an inverter. When the converter operates in inverter mode, if the AC side of the converter is connected to an AC power source and the DC power is converted into AC power of the same frequency to be fed back into the grid, it is called active inverter.
If the AC side of an inverter is not connected to the grid but directly connected to the load, i.e., it converts DC power into an AC power of a certain frequency or adjustable frequency to supply the load, it is called passive inverting. AC variable-frequency speed control operates based on this principle. Active inverting is not only used in DC reversible speed control systems but also in cascade speed control of AC squirrel-cage induction motors and high-voltage DC transmission systems.
