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Thread: Single phase / three phase
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21st July 2023, 10:17 AM #1
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Single phase / three phase
I've generally assumed that a device is single phase when I see "240 V" on the item's plate. Similarly, whenever I see "415 V" on the spec plate I assume the device requires three phase power. The following struck me as odd. Any thoughts?
I was taken by the spec plate on the side of this welder (415/440v single phase), which kind of destroyed my previous assumption. Facebook Another thing about this one, that you'd notice, is that the input current is very high.
welder.JPG
For example, here's another welder and the spec plate makes perfect sense to me: Cigweld Transmig 320SP Welder Auction (0021-7045932) | Grays Australia The plate shows 415 V, and it notes three phase, and the final giveaway is the plug design. Simple and clear.
welder2.JPG
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21st July 2023, 10:23 AM #2
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I'm going to guess the first one is designed to run off one phase of a three phase power supply. There's 415V between phases and 240V between each phase and neutral.
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21st July 2023, 10:32 AM #3
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Welders have a coil that makes them a step up transformer so while you get say 415 volts out from 240 volts in it's still only a single 415 volts you need 2 more of those to make a 3 phase machine run and then they would need to be balanced
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21st July 2023, 10:46 AM #4
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I'm just curious about this. I contacted the guy that's selling it, asking what kind of plug hangs off the end of it. That would have been a clue. But he said the plug had been removed. Damn.
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21st July 2023, 10:53 AM #5
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It may have been hard-wired.
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21st July 2023, 10:56 AM #6
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Can you clarify this please? All welders I have used are step-down. I.e. voltage out is lower than voltage in. Typically 70V. I don't think 415V at the welding rod would be safe!
Originally Posted by Camelot
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21st July 2023, 12:05 PM #7
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There are also 3 phase welders, so they will have 415 volts to deal with, the coil in a transformer type welder as a shunt which you move closer or further away from the primary and secondary windings (coils) to select the required Amperes which can range from 55 to 590 Originally Posted by jack620
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