Editing Plasma cutting (section)

==Inverter plasma cutters==
[[Image:Cnc plasma cutting.jpg|thumb|left|Plasma cutting]]
Analog plasma cutters, typically requiring more than 2 kilowatts, use a heavy mains-frequency transformer. Inverter plasma cutters rectify the mains supply to DC, which is fed into a high-frequency transistor inverter between 10&nbsp;kHz to about 200&nbsp;kHz. Higher switching frequencies allow smaller transformers resulting in overall size and weight reduction.

The transistors used were initially [[MOSFET]]s, but are now increasingly using [[IGBT]]s. With paralleled MOSFETs, if one of the transistors activates prematurely it can lead to a [[cascading failure]] of one quarter of the inverter. A later invention, IGBTs, are not as subject to this failure mode. IGBTs can be generally found in high-current machines where it is not possible to parallel enough MOSFET transistors.

The [[Switched mode power supply|switch mode]] topology is referred to as a dual transistor off-line forward converter. Although lighter and more powerful, some inverter plasma cutters, especially those without [[power factor correction]], cannot be run from a generator (that means manufacturer of the inverter unit forbids doing so; it is only valid for small, light portable generators). However newer models have internal circuitry that allows units without power factor correction to run on light power generators.