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It takes high voltage to start the arc. Once started, the air is ionized, and becomes fairly conductive. It then takes much less voltage to keep the current flowing to sustain the arc. This also...
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#2: Post edited
by
Olin Lathrop
·
2023-01-15T14:50:23Z (almost 2 years ago)
- It takes high voltage to <i>start</i> the arc. Once started, the air is ionized, and becomes fairly conductive. It then takes much less voltage to keep the current flowing to sustain the arc.
- This also explains why you have to touch the terminals together to start the arc. Touching shorts the output, which gets the current flowing to the desired level. At that point the voltage is basically 0. The welder has a large inductor in series, so that the current continues to flow immediately after the terminals are moved apart. That causes the high voltage, which ionizes the air, which allows the voltage to go down again.
This is a case where inductive kickback is actually harnessed to do something useful. Usually we design circuits so that the inductive kickback from abruptly disconnecting a coil flows somewhere harmlessly to avoid making high voltage.
- It takes high voltage to <i>start</i> the arc. Once started, the air is ionized, and becomes fairly conductive. It then takes much less voltage to keep the current flowing to sustain the arc.
- This also explains why you have to touch the terminals together to start the arc. Touching shorts the output, which gets the current flowing to the desired level. At that point the voltage is basically 0. The welder has a large inductor in series, so that the current continues to flow immediately after the terminals are moved apart. That causes the high voltage, which ionizes the air, which allows the voltage to go down again.
- This is a case where inductive kickback is actually harnessed to do something useful. As Andy pointed out in a comment, other examples are switching power supplies like boost and flyback converters. Otherwise, we design circuits so that the inductive kickback from abruptly disconnecting a coil flows harmlessly to avoid making high voltage and damaging something.
#1: Initial revision
by
Olin Lathrop
·
2023-01-15T14:16:52Z (almost 2 years ago)
It takes high voltage to <i>start</i> the arc. Once started, the air is ionized, and becomes fairly conductive. It then takes much less voltage to keep the current flowing to sustain the arc. This also explains why you have to touch the terminals together to start the arc. Touching shorts the output, which gets the current flowing to the desired level. At that point the voltage is basically 0. The welder has a large inductor in series, so that the current continues to flow immediately after the terminals are moved apart. That causes the high voltage, which ionizes the air, which allows the voltage to go down again. This is a case where inductive kickback is actually harnessed to do something useful. Usually we design circuits so that the inductive kickback from abruptly disconnecting a coil flows somewhere harmlessly to avoid making high voltage.