Tingle from TIG Welder chassis (70V AC) - Page 1
Forum section: electronics / beginners

author: Jan Catrysse
author_rank: Contributor
timestamp: January 02, 2021, 03:25:56 pm
content: Hello,I am having an issue with a Chinese TIG welder, model: AC/DC 200P. I bought it new over 10 years ago, but now I am using it for the first time. We have 240V AC with two live phase wires (L + L and not N + L).When I touch the chassis I felt quite a nasty tingle, and it seems I am having some leakage current. I was wondering if this can be fixed or if this is just how it goes on this kind of welders?The voltage is about 70V AC, the current to ground is between 0.85 and 1.25 mA AC, all 50Hz. The chassis ground and the power line earth are not connected inside the machine. I have added some pictures of the unit.I suppose this is due to some (to large) Y capacitors coupling the secondary side to the primary side. Would that be a plausible explanation? I am not sure where to find them, it's quite a complex machine at first glance and I don't have schematics.When the machine is turned on (but not welding) I measure the same 70V AC to ground on all secondary side components like the chassis, the - terminal, the + terminal, ...Any advice on this situation? Is it a problem? How could I fix this? Would it suffice to find and replace the Y caps by smaller ones?Thank you.Jan

author: rstofer
author_rank: Super Contributor
timestamp: January 02, 2021, 05:41:07 pm
content: Quote from: Jan Catrysse on January 02, 2021, 03:25:56 pmOther than double insulated tools, like some drill motors, everything is supposed to be grounded to earth. The National Electric Code has a statement in Article 250 similar to: "All exposed non-current carrying metallic surfaces shall be grounded". I left my book behind when I retired...That cabinet is certainly a metallic surface and it isn't intended to carry current so it should be grounded.It will be important on the output as well. I would expect the ground clamp to be earth grounded as well.

author: The Soulman
author_rank: Super Contributor
timestamp: January 02, 2021, 06:11:27 pm
content: Quote from: Jan Catrysse on January 02, 2021, 03:25:56 pmThe yellow/green ground wire should always be connected on the metal chassis, that would cure any stray voltage on the outside andmakes sure your rcd trips when anything is wrong inside the welder (bad Y caps, moisture ingress etc etc.).The pictures do show some connections but they are only from chassis to panel?

author: Monkeh
author_rank: Super Contributor
timestamp: January 02, 2021, 06:33:20 pm
content: There's a gigantic earth terminal and a likely very pertinent label on the back you've carefully not taken a photo of in focus.Quite frankly you should throw it away and buy something properly built, along with anything else which gives you a belt when you touch it, before you end up dying of being cheap.

author: Jan Catrysse
author_rank: Contributor
timestamp: January 02, 2021, 06:54:55 pm
content: This is the label (attachment). I have grounded the unit with that terminal (and with the power cord ofcourse).BTW: it wasn't cheap!

author: Gregg
author_rank: Super Contributor
timestamp: January 02, 2021, 08:23:14 pm
content: In order to get a shock from the chassis, you have to be part of a circuit! What else are you connected to when you touch the chassis? If you are touching one of the electrodes and then the properly grounded chassis, you become part of the circuit.However your body can become a pole of a capacitor.If the welder has a high frequency start feature, you can get a nasty zap from the tig torch even though you are isolated from ground. Perhaps your ground connections are not adequately connected to real ground which can lead to really scary things.I still remember RF burns from ham radio days from just touching something metal not connected to the radio equipment.

author: CaptDon
author_rank: Super Contributor
timestamp: January 03, 2021, 12:17:43 am
content: The power cord should have a green or green/yellow wire connectedto chassis and of course 3 pins at your wall socket which includes theground back to real earth. Is this just a 2 pin power cord??? If so thatsucks. If it is a 3 pin and you still have 70 vac on the chassis then theground in your shop wiring is suspect!!

author: Jan Catrysse
author_rank: Contributor
timestamp: January 03, 2021, 09:37:08 am
content: Thank you for the comments.After some thoughrow investigation it seemed two of the three power outlets in the shop had a bad ground! The ground cable inside the outlet was not completely inserted and wasn't making a contact to the ground pin.It is fixed now and no more tingle.Thank you.

author: gcewing
author_rank: Regular Contributor
timestamp: January 03, 2021, 01:21:09 pm
content: Quote from: Jan Catrysse on January 03, 2021, 09:37:08 amLike the sticker says, your house needs to be reliable!