Plasma Cutting - selecting the best start type
Little thought is given by most purchasers of plasma cutting systems about the starting of the arc, and how it is accomplished within the unit. But this is an important issue that the purchaser should be aware of, because each of the three major start types offer distinct advantages and disadvantages. Below are a list of the three basic types, and what you need to know to make the best choice for you when selecting a plasma cutter.
1) “Blowback” start. This start type uses air pressure supplied to the cutter to force a small piston or cartridge inside the torch head back to create a small start between the inside surface of the consumable, ionizing the air, and creating a small plasma flame. This also creates a “pilot arc” that provides a plasma flame that stays on, whether in contact with the metal or not. This is a very good start type that is now used by several manufacturers. It’s advantage is that it requires somewhat less circuitry, and is a fairly reliable.
2) High Frequency start. This start type is widely employed, and has been around the longest. Although it is older technology, it works well, and starts quickly. But, because of the high frequency high voltage power that is required generated to ionize the air, it has some drawbacks. It often interferes with surrounding electronic circuitry, and can even damage components. Also a special circuit is needed to create a Pilot arc. Inexpensive models will not have a pilot arc, and require touching the consumable to the work to start. Employing a HF circuit also can increase maintenance issues, as there are usually adjustable points that must be cleaned and readjusted from time to time.
3) A much less, common and more expensive start time, is an inductor circuit start. This uses a high voltage, lower frequency current to ionize the air. Torches are similar to the HF torches, if not identical. The start is very quick, and interference is minimal. However, it is a more costly design, due to the component requirements to make such a design. This start would seem ideal compared to HF and blowback, if the cost was more reasonable. Very few companies use this design, because of it.