Development of DC power supply for electrochemical machining

At present, most of the electrolytic machining production at home and abroad still uses DC power supply. Electrochemical machining DC power supply early use of DC generator set, its advantages are stepless voltage regulation, stable performance, reliable use, its disadvantages are large footprint, large noise, low efficiency, poor sensitivity to adjust the mind, resulting in low voltage stability accuracy, short circuit protection time. With the development of high-power silicon diodes, silicon rectifier power supplies have gradually replaced ECM DC power supplies DC generator sets. Its main advantages are high reliability, good stability, high efficiency and high power factor. The simple type of silicon rectifier adopts autotransformer voltage regulation, no voltage regulation control and short circuit protection, and can also use saturated reactor voltage regulation and voltage regulation, but its adjustment sensitivity is low, short circuit protection time is longer (about 25ms), the voltage regulation accuracy is not high enough, only about 5%, and the consumption of copper and iron is large, and the economy is not good enough. With the development of high-power thyristor devices, the DC power supply of thyristor voltage regulation and voltage regulation has gradually replaced the silicon rectifier power supply of ECM DC power supply. Now all foreign countries have adopted this kind of power supply, and the domestic high-current power supply also adopts this scheme. Its main advantages are high sensitivity, voltage stability accuracy up to 1%, short circuit protection time up to 10mS. If the fast thyristor protection device is configured, the protection time can reach the microsecond level. The failure rate of the early SCR power supply is high because of the unstable performance of the high-power SCR tube, the small capacity, the complicated problem of multi-channel parallel current sharing, and the unstable performance of the triggering system of discrete components. In recent years, the large-capacity modular thyristor, GTO (turn-off thyristor) and the trigger unit of the integrated block have better solved the reliability and stability of the power supply. Another advantage of SCR rectifier power supply is high efficiency, saving copper, saving iron, good economy, but in the deep control of the opening Angle is small, the equivalent power factor is low.

Large capacity SCR power supply mostly uses water cooling, water quality must be controlled to prevent dirt blocking the cooling channel. The small volume Limulus thyristor power supply can still be air-cooled. The main circuit is divided into two categories: primary side controllable and secondary side controllable. The primary side loop can be started by Y/A step-down, the secondary side loop of the small unit power supply uses three-phase bridge rectifier, and the double star inverse parallel loop is used for large capacity.