It depends on the size of the machine you choose. MOS tube DC welding machine is generally maximum to 315A. IGBT made from 200A. Generally 200A to 400A are using a single tube IGBT500A is using the module IGBT.
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Tell the truth. Now the technology of MOS tube is also very mature. So if your electrode is in 3.2. It is recommended to buy a machine with MOS tube. If you want to burn 4.0 electrode, buy IGBT. Now more than 315 machines are divided into industrial machines and civil machines. The amount is not large. Just use the civilian jet. High volume industrial machine.
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Put it this way. A 400A machine is basically composed of 20 MOS tubes and a single tube is 4. The module consists of two components. One of the bad ones. Machines break down.