Why has DIYNOT got a electrics forum?

[Big_Spark]

........................

Oilman, you are correct that the PD across phases is 415V, but your forgetting that you would also be in contact with the general mass of earth, unless levitating, as a result you would be susceptible to the fact that each phase IS 120 degrees out of phase with respect to each other (240V phase-Earth or Neutral) and in this situation it is the effect of the frequency oscillations on the heart, so I am led to understand, that does the damage.

Of course 415V coursing through your body is not going to be a pleasant experience, but the effect of three or even two serices that are both at 50Hz and 120 degrees out of phase will not be good for the heart.

You cannot go around making statements like this and expect to get away with it. Unless you stand on damp earth, in bare feet, you will probably be in reasonably well insulating shoes or boots, and on a floor which will be a poor conductor. In that case the connection to earth will be capacative, and the impedance will mean the phases will be something other than 120 degrees, AND the current and voltage will not be in-phase.

415V does not course anywhere, it is merely the pressure which causes the coulombs to move.

Oil, for a start you being pedantic on some of your comments...and also the supply frequency is set at 50Hz and 120 degrees apart by the generator set..now I agree and accept that circuit condition will alter aspects of the way the circuit works....however the smple fact is the heart will still be subjected to three different voltages at alternating frequencies...Yes the phase to phase voltage will be 415V, but the frequencies of the supply are still there, and they will effect the heart...unless you change the laws of physics that is incontravertible....now I am no doctor so what the exact effect on the heart would be I have no idea, but a single phase supply has a single frequency of 50Hz, and the heart cannot beat at this frequency, now imagine it attempting to enter sync with two or three services 120 degrees apart....as it tries to beat one way it would also be trying in another...it would likely stop....

 

[oilman]

.......Anyway..the reason you will recieve a shock greater than the resistance of the body is due to resistance in series. If your in parallel with the supply, as you and I have agreed on, it is your body resistance that counts, but if your in series with the circuit, and your not grounded out elswhere, then you will be a resistor of 1500 Ohms in series with the supply...and this will be added to the resitance of the rest of that circuit, so you will recieve a shock at the full load of that circuit....which will be the resistance of the circuit added to the resistance of the body...

As the great one says "FFS"

What laws of physics do you use? Resistance of body is 1500 ohms. Gives rise to a current. Yes? Resistance of body plus motor is 1530 ohms. Gives rise to less than first current. Yes?

Either your writings are a bit confused after a long day causing road accidents, or your understanding of physics is lacking. Which is it?

[/quote]

 

[ban-all-sheds]

Anyway..the reason you will recieve a shock greater than the resistance of the body is due to resistance in series. If your in parallel with the supply, as you and I have agreed on, it is your body resistance that counts, but if your in series with the circuit, and your not grounded out elswhere, then you will be a resistor of 1500 Ohms in series with the supply...and this will be added to the resitance of the rest of that circuit, so you will recieve a shock at the full load of that circuit....which will be the resistance of the circuit added to the resistance of the body....

The calculation for resistors in series is Ra + Rb + Rc +...

So let us assume that the circuit resistance is 5 ohms? We can use another figure if you like, either higher or lower, it's up to you.

But staying with 5 ohms, we have, therefore:

---- L
|
|
>
<
> 5 ohms
<
>
|
|
|
>
<
> 1500 ohms
<
>
|
|
---- N

So unless you want to claim that I = V/R is no longer true, that means:

I = 230/(5 + 1500) = 230/1505 = 152.8mA.

Enough to spoil your day, but not "the full load of the circuit" (if I understand correctly what you mean by that).

And 0.5mA less then what you'd get if you put yourself directly across L-N....

 

[Big_Spark]

Are you two being deliberately stupid or simply being obtuse?

The FULL LOAD OF THE CIRCUIT IS THE TOTAL OF ALL RESISTANCES (ETC) FORMING THAT CIRCUIT...

So the body resistance PLUS the normal circuit resistance IS THE FULL LOAD CURRENT OF THE CIRCUIT...remember you have become part of the circuit....by completing the circuit you are becoming part of the circuit..as I have said...thus the full load is as I have said... I have not said that you would necessarilly recieve a shock greater than normal..I simply said the full load current of the circuit...

...Which language do you want it in FFS....

I thought I was typing it wrong, but I am not, it is you lot not reading what I am typing...

 

[oilman]

........................

Oilman, you are correct that the PD across phases is 415V, but your forgetting that you would also be in contact with the general mass of earth, unless levitating, as a result you would be susceptible to the fact that each phase IS 120 degrees out of phase with respect to each other (240V phase-Earth or Neutral) and in this situation it is the effect of the frequency oscillations on the heart, so I am led to understand, that does the damage.

Of course 415V coursing through your body is not going to be a pleasant experience, but the effect of three or even two serices that are both at 50Hz and 120 degrees out of phase will not be good for the heart.

You cannot go around making statements like this and expect to get away with it. Unless you stand on damp earth, in bare feet, you will probably be in reasonably well insulating shoes or boots, and on a floor which will be a poor conductor. In that case the connection to earth will be capacative, and the impedance will mean the phases will be something other than 120 degrees, AND the current and voltage will not be in-phase.

415V does not course anywhere, it is merely the pressure which causes the coulombs to move.

Oil, for a start you being pedantic on some of your comments...and also the supply frequency is set at 50Hz and 120 degrees apart by the generator set..now I agree and accept that circuit condition will alter aspects of the way the circuit works....however the smple fact is the heart will still be subjected to three different voltages at alternating frequencies...Yes the phase to phase voltage will be 415V, but the frequencies of the supply are still there, and they will effect the heart...unless you change the laws of physics that is incontravertible....now I am no doctor so what the exact effect on the heart would be I have no idea, but a single phase supply has a single frequency of 50Hz, and the heart cannot beat at this frequency, now imagine it attempting to enter sync with two or three services 120 degrees apart....as it tries to beat one way it would also be trying in another...it would likely stop....

It can't beat at 50Hz either.

For "pedantic", read accurate.

How is it there is Big-sparks version of physics, which differs from everyone elses (you know, all the luddites posting here)?

 

[Big_Spark]

Oil, are being deliberatly obtuse? I said the heart cannot beat at 50Hz...FFS READ the post as I wrote it, not as you wish it to read..

Heart Failure caused by this action is called Ventricular fibrillation...I do believe I said this in an earlier post...

http://www.americanheart.org/presenter.jhtml?identifier=4784

 

[Big_Spark]

.......Anyway..the reason you will recieve a shock greater than the resistance of the body is due to resistance in series. If your in parallel with the supply, as you and I have agreed on, it is your body resistance that counts, but if your in series with the circuit, and your not grounded out elswhere, then you will be a resistor of 1500 Ohms in series with the supply...and this will be added to the resitance of the rest of that circuit, so you will recieve a shock at the full load of that circuit....which will be the resistance of the circuit added to the resistance of the body...

As the great one says "FFS"

What laws of physics do you use? Resistance of body is 1500 ohms. Gives rise to a current. Yes? Resistance of body plus motor is 1530 ohms. Gives rise to less than first current. Yes?

Either your writings are a bit confused after a long day causing road accidents, or your understanding of physics is lacking. Which is it?

[/quote]

Niether Fella..it's the way you have read my posts..read the one with the example in it.. and read the second from last post of mine...

I never said the current would be more, I simply said the full load current of the circuit...It was simply how you chose to read it...

 

[oilman]

Oil, are being deliberatly obtuse? I said the heart cannot beat at 50Hz...FFS READ the post as I wrote it, not as you wish it to read..

Heart Failure caused by this action is called Ventricular fibrillation...I do believe I said this in an earlier post...

http://www.americanheart.org/presenter.jhtml?identifier=4784[/QUOTE]

So what's the relevance of the three phases then? Answer= none. It's just another red herring.

 

[Big_Spark]

Oil..it's not a Red Herring...

You should remember that a three phase supply is three potential differences (in respect of Earth) that are 120 degrees out of phase as determined by the method of generation. Each of these Pd's has a frequency of 50Hz, again as determined by the alternator at the origin of the supply. Now if you connect yourself across two or three of these phases, the heart will recieve not one PD, but three, all operating at 50Hz but 120 degree apart. Instead of attempting to beat at 50 times a second (which it cannot), it will try to react to all three of the seperate frequencies caused by the individual phases..these individual phases will attempt to cause the heart to beat or whtever to their "rythmn", but it will be trying to do two or three motions at the same time..and it generally causes massive damage to the heart tissue..

 

[slippyr4]

Look, re-read my post from yesterday, and your own.

You were saying that if you completed a circuit which originally had say, 5 amps going through it, you'd get 5 amps through you. Which is crap.

I pointed out that it was crap, using ohms law.

You disputed that,

Now you come out with an example to "prove yourself right", which is basically exactly the same as my argument in the first place.

You're trying to twist the wording of what you wrote to stop yourself looking like an idiot, and it's not working.

 

[Big_Spark]

Slippy..I apologise..I was about to have a pop but thought I would re-read my other posts first...I see what you mean..I posted a message which certainly gave that impression and the statement is totally incorrect..bad checking by me.....

Had I gone back and checked earlier I think we would have not have got to a confused position with us both saying the same thing but confused by my bad post...

Please accept my apologies for that..I think you can see we actually agree, I understand why you seemed to be arguing against what I said...

 

[oilman]

Alleluia

 

[Big_Spark]

Oil..I am big enough to apologise when I make a mistake...perhaps others in this thread might like too as well...

 

[slippyr4]

smashing, all sorted then, and ohm's law still applies.

I think that calls for a celebration, so I shall crack open another tin of bitter juice, as we all should.

 

[ban-all-sheds]

Are you two being deliberately stupid or simply being obtuse?

I, and I expect a number of others, have noticed something. I wonder if you have?

I wonder if you have noticed how many times over the years you've come out with stuff that a lot of others have argued with (as in saying you are factually wrong rather than arguing over opinions and beliefs) and you've ended up complaining that everyone has deliberately misunderstood or misinterpreted what you've said?

The FULL LOAD OF THE CIRCUIT IS THE TOTAL OF ALL RESISTANCES (ETC) FORMING THAT CIRCUIT...

So the body resistance PLUS the normal circuit resistance IS THE FULL LOAD CURRENT OF THE CIRCUIT...remember you have become part of the circuit....by completing the circuit you are becoming part of the circuit..as I have said...thus the full load is as I have said...

Yes, and you've consistently said it in a way that meant you were claiming that this "full load current" was the current that would have flowed in the circuit if there'd been the normal conductor connection to complete it:

But your forgetting that electrical circuits do not exist in a state of zero current. Usually when people recieve a shock, the circuit is under load and when you short that circuit you recieve a full shock equivilent to the load on the circuit and some.

What I should have pointed out is that the majority of fatal shocks occur not from touching the phase conductor, but from creating a circuit across the neutral or acroos the load of an appliance, so that the person recieves the full load shock....

however if the circuit is energised, connecting the neutral would allow the full load being drawn to flow

IF YOU connected the neutral across your body then you have completed an electrical circuit, the circuit would energise as if you were not forming the bridge (assuming the neutral was intact) and at that time the load of the circuit would flow through you, just as if you were a piece of wire in the circuit..albeit with a lot higher resistance than wire...

I have not said that you would necessarilly recieve a shock greater than normal..I simply said the full load current of the circuit...

You may try to wriggle out of it now, but I doubt that anyone will believe that you were not at the time intending to claim that completing a circuit by joining a broken neutral would result in a more severe shock than you'd get if you bridged P-N or P-E.

This disbelief stems from two things.

1) The fact that when you initially claimed it, and people said "no it doesn't work that way, it's just ohms law, and the resistance of your body will determine the current", at no time did you say "that's what I meant, the full resistance of the normal load plus the resistance of the body", you kept on arguing and going on about this "full load current".

2) Your assertion that there is some different mechanism:

I appreciate that this situation is one most people never find themselves in, 95% of electric shocks are phase to earth and in that situation, as everyone agrees, the current flowing would be determined by the resistance of your own body and the potential difference flowing across it, this is the same for Phase to neutral shocks.

It's also the same for shocks that you get if you join a broken neutral or a broken phase. But you would not have written what you did if you didn't think it was different.

In neither situation do you become part of the electrical circuit, you ARE the electrical circuit,

In all situations you become part of the circuit. You may become the only path or you may become a parallel path, but you are part of the circuit.

but if you bridge the neutral via your body, and the circuit is energised, at the moment of energisation, the full potential current of the circuit will flow across you

There you go again with this "full potential current" as if it is something wholly different to the current that you'd receive via some other way of connecting yourself into the circuit.

I thought I was typing it wrong, but I am not, it is you lot not reading what I am typing...

Sometimes you remind me of the soldier in a column of marching men who thought that he was the only one in step, and all the others were out of it...

I never said the current would be more, I simply said the full load current of the circuit...

You did say it would be more:

It is often not realised by many that the shock hazard of the neutral conductor is far higher than that of the phase conductor.

To my way of thinking a higher shock hazard means that you'll get more current flowing in you when you touch the neutral than if you touch the phase, not less.

BAS..the point I was making is that there is a significant difference between a shock from Phase to earth, where the current flowing in your body will be determined by your body's resistance, as for any electrical circuit, BUT if you complete a circuit by making the connection ACROSS A BROKEN NEUTRAL, then the shock you recieve will be the current flowing in the circuit at that time..you will effectively become part of the circuit rather than a seperate circuit..(as with a Phase to neutral or Phase to earth shock)

An explicit statement to the effect that if you make yourself "part of the circuit" by putting yourself across a broken neutral, that there will be a significant difference between the shock you get, and the shock you would get if you put yourself between phase and earth. Given that you've said the shock hazard is higher, you are saying that the current that would flow in you would be significantly higher than the current that would flow in a phase-neutral or phase-earth shock.

Why did you say "a shock from Phase to earth, where the current flowing in your body will be determined by your body's resistance, as for any electrical circuit, BUT if you complete a circuit by making the connection ACROSS A BROKEN NEUTRAL, then the shock you recieve will be the current flowing in the circuit at that time" if you didn't mean to say that the current flowing would not be determined by your body's resistance but would be determined by some other mechanism?

Even your example contradicts what you were claiming.

First a quick re-cap:

95% of electric shocks are phase to earth and in that situation, as everyone agrees, the current flowing would be determined by the resistance of your own body and the potential difference flowing across it, this is the same for Phase to neutral shocks.

OK - in your motor example, a body at 1500 ohms:

Phase to earth (do you mind if I ignore Ze??) 230/1500 = 153.3mA
Phase to neutral 230/1500 = 153.3mA

Completing a broken neutral in series with the motor 230/1530 = 150.3mA

3mA less

It is often not realised by many that the shock hazard of the neutral conductor is far higher than that of the phase conductor.

I've just realised that you were right all along - that indeed is not realised by many...