ELV electric shock

[Dambo]

With ELV is there enough current generated to give a person an electric shock? ?:|

 

[Apache]

**load of tripe**

:coat

 

[Riggy]

No!

ELV = Extra Low Voltage (<50Vac)

Not enough voltage to generate a "shock" current through the resistance of a human body.

 

[SPECIAL LOCATION]

Erm...

Is not ELV isolated by a transformer...

there is NO return path to complete a circuit through the body..

Thus No path for an electric shock,

e.g.

same principal as an isolating transformer used on shaver sockets..

Although a typical shaver output is at 240v/110v It is NOT part of the earthing system that the supply come from.

The physical cables are completely isolated.

ELV transformer as well as dropping the voltage will also provide Isolation.



{unless o course you've done something daft like use an Autotransformer and/or tied one leg down to earth potential! :_| ] }

 

[Riggy]

Erm...

Who said to earth? ROTFWL

 

[SPECIAL LOCATION]

Erm...Who said to earth? ROTFWL

I thought you were going to say...

Erm "ELV" Not "SELV" {sharp intake of breath}:OBlushing:^O

Guinness

 

[Andy™]

even at SELV, if you touch both lives at the same time, current can flow through you. however, due to resistances etc, current flow will be very low, so no damage, and chances are you wont feel anything

 

[Dambo]

Just a couple of things I don't completely understand:

1) It only taken 1mA for a person to be aware of electric current - Surely there must be more current flowing than this i.e. an electric shock could occur?

2) Special Location mentioned above that with the transformer there is no return path to complete a shock through the body - Does a transformer completely isolate the circuit in question?

 

[roys]

Although you may be able to just about feel 1mA there is not enough voltage there to 'drive' it through your body (resistance of your body), hence the reason for low voltage. That is why you can touch the positive and neg of a car battery and not feel it, as there is only 12V there. However there is tons of amps available in order to turn the engine over.

 

[Dambo]

I thought it was the amps that did the damage though and not the volts?

 

[Andy™]

I thought it was the amps that did the damage though and not the volts?

it is the amps. but unless you get the voltage, you wont get enough current to flow.

 

[Andy™]

Just a couple of things I don't completely understand:2) Special Location mentioned above that with the transformer there is no return path to complete a shock through the body - Does a transformer completely isolate the circuit in question?

an isolation transformer has no reference to earth. there is only a voltage between both lives. unless your touching both lives, there isnt a return path, so no shock

 

[aptsys]

If the skin is broken at both contact points, then yes.

 

[sellers]

I thought it was the amps that did the damage though and not the volts?

Yes, but without enough voltage the amps wont be passing through your body to kill you.

You could have a car battery at 12v 70A, touch both terminals and your a-ok.

Now go back into your house touch a live cable at 230v but only 50mA and you could be a dead man. Up the ampage, stand in a field (less resistance) holding a live cable and you'll be well through thos pearly gates.

 

[Andy™]

Yes, but without enough voltage the amps wont be passing through your body to kill you.You could have a car battery at 12v 70A, touch both terminals and your a-ok.

Now go back into your house touch a live cable at 230v but only 50mA and you could be a dead man. Up the ampage, stand in a field (less resistance) holding a live cable and you'll be well through thos pearly gates.

the amps that something can supply doesnt have anything to do with this. your just adding to confusion by saying a car battery is at 70A but your fine, and then 230v is 50mA. a car battery may be able to supply 70A, but there wont be 70A flowing if you touch it. and a 230V supply is not always a 50mA shock

 

[Dambo]

[quote name='Andy

 

[Andy™]

So would it be fair to say that the resistance of your body is much higher than the ELV (50V)?

your body resistance is the same at ELV as it is any other voltage. difference being, less voltage means less current can flow

 

[Dambo]

[quote name='Andy

 

[Dambo]

[quote name='Andy

 

[Andy™]

So why if I only touch one live will nothing happen? Sorry to sound like an idiot, it's just that I can't get my head around how if you did that on a normal circuit the RCD would trip but in this instance nothing would happen. headbang

on a normal transformer feeding our house etc, one side is connected to ground and used as an earth throughout. this side is neutral. the other side is the live (ignoring it being 3 phase for now). this live is at 230v between neutral and earth. touch this, and you will complete the path through your body to ground and back to tansformer.

with an isolation transformer (such as SELV), nothing is 'earthed'. so voltage (and current) can only flow between both lives. if you touch one live, because the other side isnt earthed, you dont complete the circuit and stay alive