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At an industrial plant, we have three electrolytic cells supplied with a 6 V Rectifier (max current 10 kA).

Each of the three cells is currently absorbing ~1000 A at 6 V through 8 240 mm² copper cables (for each one).

My concern is with safety because the connection points are now reachable by operators. We are thinking on how much effort should we put into insulating and securing the instalation but I am thinking, isn't 6 V safe for any human to touch a conductor (and not being earth protected) or even grab the two poles? I know the current can be high but as far as I know a human being would not absorb a dangerous amount of current at 6 V.

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    \$\begingroup\$ "10 kiloamperes." You need to consult the regulations for your industry and your country. This is the kind of thing that can go very bad, very quickly. When you get investigated after an accident and you tell the authorities "I asked some random people on the internet and they said it was OK," then you might get away with it - if the authorities laugh themselves to death before they lock you up and fine your company out of business. \$\endgroup\$
    – JRE
    Jan 11, 2021 at 12:30
  • \$\begingroup\$ Just as an example of things you haven't thought of: Did you know that the magnetic field around the bus bars and cables can magnetize equipment and cause failures? \$\endgroup\$
    – JRE
    Jan 11, 2021 at 12:31
  • \$\begingroup\$ You need to find the safety regulations and get in compliance before somebody gets hurt or killed - or your factory burns down and releases toxic smoke and chemicals into the environment. \$\endgroup\$
    – JRE
    Jan 11, 2021 at 12:33
  • \$\begingroup\$ 10000 amps is a lot of amps. What about the magnetic field? What happens if someone is wearing a watch? \$\endgroup\$
    – user253751
    Jan 11, 2021 at 13:01
  • \$\begingroup\$ I would not rely on Stack Exchange for safety. I would hire someone to do a safety assessment and implement their findings. Stack Exchange can give you an idea of what kind of things might happen, but you will need a professional to see what problems there are at your particular plant. \$\endgroup\$
    – user253751
    Jan 11, 2021 at 13:02

3 Answers 3

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Nothing much should happen from touching it, but you wouldn't want someone dropping a set of keys on it. Insulate it.

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6 V is well below the voltage reckoned to be 'touch safe' by most authorities.

However, it would make a real mess of a spanner or other metallic tool dropped across the terminals. You need to take steps to ensure that nothing metallic can accidentally contact them.

Insulation is one way. Constructing suitable guards is another.

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    \$\begingroup\$ @Jorge: Think of wrist-watches, rings, etc., and the amount of current that would flow in a short-circuit. \$\endgroup\$
    – Transistor
    Jan 11, 2021 at 9:54
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    \$\begingroup\$ You are all right, but when confronted with the 2 meters-high rectifier with a 10000A max current sticker no engineer in the plant has dared to grab + and -. We all know the theory, 6 V is nothing, but it scares a lot. \$\endgroup\$
    – Jorge
    Jan 11, 2021 at 10:11
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    \$\begingroup\$ @Jorge totally wrong approach! You're not securing this against what engineers do intentionally, but against what happens unintentionally. For example, through bad luck, an aluminium foil piece gets blown into this. No substantial damage done, it just evaporates in a bright flash of light, permanently damaging the janitor who was cleaning nearby. \$\endgroup\$
    – Marcus Müller
    Jan 11, 2021 at 10:26
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    \$\begingroup\$ @Jorge much more realistically, someone is working on something nearby, and a tool falls, hits the ground, and jumps into the contacts, then splattering molten tool steel all around. These things should be behind e.g. plexiglass thick enough to guard at least against likely hishaps. If this is a floor with forklifts, there needs to be enough protection against these. \$\endgroup\$
    – Marcus Müller
    Jan 11, 2021 at 10:27
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    \$\begingroup\$ I see, thanks all! \$\endgroup\$
    – Jorge
    Jan 11, 2021 at 10:31
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A screwdriver or wrench shorting the terminals will explode into gas and sputter hot particles into plastic safety lenses over a 2m distance easily.

Inductance will then create kV fly back when the current stops abruptly.

You decide what is safe and how to manage that with suitable protection.

MW DC busbars are made by my partner using thin laminates for low skin effects on arc loads up to 10kA with very high SRF.... let me know if you need this.

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  • \$\begingroup\$ Why do you need to avoid skin effect with DC? \$\endgroup\$
    – user253751
    Jan 11, 2021 at 14:40
  • \$\begingroup\$ DC is just a supply yet arc loads are extremely broad spectrum, so better power transfer \$\endgroup\$
    – Tony Stewart EE75
    Jan 11, 2021 at 16:39
  • \$\begingroup\$ Its quite difficult to short the terminals since they are 1,5m appart and separated by the cells liquid. \$\endgroup\$
    – Jorge
    Jan 11, 2021 at 21:34
  • \$\begingroup\$ Then update your question with the facts. Are they floating voltages? or shunted to safety ground with caps? \$\endgroup\$
    – Tony Stewart EE75
    Jan 11, 2021 at 22:02

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