Bare 50Hz AC 3 Phase Bus bars...what is safe voltage to use

[treezleef]

Hi Hi,
We will have isolated three phase bus bars. Fully Mains transformer isolated. (mains input is 240VAC phase to neutral)
We're going to step down the 3 phase mains to the bus bars using a 50Hz 3 phase transformer.
What is the highest VAC level that these bare bus bars can be at and not be a danger to humans touching them?
(ie touching one bus bar, and also touching between two bus bars with each hand)

Also, i presume we have to have the neutral output of the three phase transformer earthed...otherwise the 3 phase output will be floating and could potentially float up to a dangerous level?

 

[westward10]

50vac is considered to be safe electric shock wise however it can still subject you to pain and possible injury, maybe not an electrical injury but from the result of falling for example. You must provide basic protection.

 

[Pete999]

Hi Hi,
We will have isolated three phase bus bars. Fully Mains transformer isolated. (mains input is 240VAC phase to neutral)
We're going to step down the 3 phase mains to the bus bars using a 50Hz 3 phase transformer.
What is the highest VAC level that these bare bus bars can be at and not be a danger to humans touching them?
(ie touching one bus bar, and also touching between two bus bars with each hand)

Also, i presume we have to have the neutral output of the three phase transformer earthed...otherwise the 3 phase output will be floating and could potentially float up to a dangerous level?

Depends on the rating of the BBs

 

[snowhead]

Way too many questions.
I'll try one.
Are these Bus bars in a building in the U.K? (I know it says Southampton on the O.P profile)

 

[Lucien Nunes]

Whatever the voltage, there is a risk of burns or arc flash if the source impedance is low enough. Even at say 5V, a high current supply could cause life-changing injury if metal jewellery shorted the busbars together. As already stated, if these are a supply of energy, rather than perhaps a signal source referenced to the AC mains through a high impedance, then it will not generally be acceptable for them to be exposed. What is the application?

 

[treezleef]

The application is an "art" gallery displaying multiple exhibits of interest.
Also, we are in UK.
So if we keep the bus bars below 50VAC then we will be OK? They are after all, isolated from the mains.

 

[DPG]

Why not just stick to 12V? Is it just to light lamps? Give us some more info.

 

[pc1966]

As above, 50V AC is considered "safe" for situations where contact is not expected and water is not present, but high current can cause serious burns. For at-risk areas like swimming pools it is usually taken as 25V or less.

If it is simply for some art display then go for 12-24V or similar but make damn sure it is current limited to a could of amps at most, that should still allow some reasonablt amount of lights or small motors to be run from it.

 

[freddo]

I'm intrigued by the need for 3 phase?

 

[DPG]

I'm intrigued by the need for 3 phase?

Same here. The OP seems reluctant to give much info.

 

[ipf]

Sounds dicey to me. Not enough info and whiffs of DIY.

 

[StephenRowley]

What do mean for a art gallery display?

Is it for lighting?
Power items in Said display?

I'm intrigued

 

[ipf]

What do mean for a art gallery display?

Is it for lighting?
Power items in Said display?

I'm intrigued

Maybe it's just available...can't think of any other reason.

 

[ElectroChem]

I'm thinking some kind of silly interactive 'modern art' exhibit. "Grab the busbars, it's perfectly safe!" No thanks, I've seen the autopsy reports from electrocutions.

 

[Wilko]

For what it’s worth, Class lll appliance design might be of interest. A suspended bare cable light system might be designed for this class and they are usually 12V, supplied by certified isolation transformer etc.