Domestic Vs Industrial

[Ryan_Moore]

Hi Sparks!
I am hoping to become an apprentice very soon and I have a question for you all,
What is the difference between the 230v single phase used in domestic buildings and the 415v used in commercial/industrial buildings. Also why is it necessary for there to be a difference, what are the pros and cons of each.


Also I have heard rumours of all new builds now having electric heating, does this mean less work for plumbers and gas fitters and more work for us....or you I should say at the moment, give me a few years

 

[Des 56]

Voltage at point in time t

Isn't "Instantaneous value",easier for us to say when we are drunk

 

[topquark]

Voltage at point in time t

Isn't "Instantaneous value",easier for us to say when we are drunk

But, but I haven't had a drink for ages sir

 

[Des 56]

But, but I haven't had a drink for ages sir

I trust for the benefit of Ryan J Moore,that was the only post you made that was a little short on the truth :8:

 

[Ryan_Moore]

Or very true, a drunken spark giving me advice might not be the best thing

 

[topquark]

I trust for the benefit of Ryan J Moore,that was the only post you made that was a little short on the truth :8:

I have to say I've been good ... haven't posted any obviously misleading information for a long time. (It's been alleged I have a wicked sense of humour ... don't know where anyone would get that idea from).

 

[Ryan_Moore]

Maths question: the sine graph passes through 0 and peaks at 1 and -1 on the y axis, applying this to our electricy stuff, it would pass through 0 ( ie no volts at no time) and peak at 240 and -240 right?

On a single phase this is fine, you have 1 sinx graph and that is that, however when you have 3 phases you end up with 2 translations of the sine graph along with the original, if you translate sin by (-90,0) (I think it my translations arent great) you get the graph of cosx so on 1 axis you have sinx,sin(x+a) and cosx. and each of these represents a phase? At any time(any x value) you have 3 possible solutions(one per graph)

you know what I am gettin too much into this, I need to be patiant and wait til I am actually a apprentice, I am too damn excited now!

 

[Ryan_Moore]

I have to say I've been good ... haven't posted any obviously misleading information for a long time. (It's been alleged I have a wicked sense of humour ... don't know where anyone would get that idea from).

With a tag that says "children on backseats cause accidents, accidents on backseats cause children" I think that is an awesome sense of humour

 

[topquark]

Maths question: the sine graph passes through 0 and peaks at 1 and -1 on the y axis, applying this to our electricy stuff, it would pass through 0 ( ie no volts at no time) and peak at 240 and -240 right?

Yes, but remember that's just a voltage that's present. It has to be measured between that point and somewhere else, either 0 volts or one of the phases to derive the potential difference and hence be able to drive a current (remember it's Alternating Current we're interested in, not the voltage).

On a single phase this is fine, you have 1 sinx graph and that is that, however when you have 3 phases you end up with 2 translations of the sine graph along with the original, if you translate sin by (-90,0) (I think it my translations arent great) you get the graph of cosx so on 1 axis you have sinx,sin(x+a) and cosx. and each of these represents a phase? At any time(any x value) you have 3 possible solutions(one per graph)

Stick to using Sin, that's all you need. The phases are 120 degrees out of phase with each other. If we label them P1 P2 and P3 then when P1 is at 0 degrees, P2 will be at 120 degrees and P3 at 240 degrees.


you know what I am gettin too much into this, I need to be patiant and wait til I am actually a apprentice, I am too damn excited now!

Keen is good ... just don't come across as hyper or impatient in the interview

 

[Ryan_Moore]

So for a fraction of a second, 1/50 of a second I think, according to the sin graph, something can have 0v?

 

[malcolmsanford]

Nope. Just a poor domestic/commercial spark.

To quote a Western movie Idiom.

" You speak with fork tongue" Just a poor domestic/commercial spark,:devilish:

 

[topquark]

So for a fraction of a second, 1/50 of a second I think, according to the sin graph, something can have 0v?

I'm being cautious with my wording now, as it wouldn't be for a whole 1/50 of a second (as it's continually changing and will complete one complete cycle from 0 to +240 to -240 and back to 0 in 1/50th of a second). The accuracy of the time period at which it is 0V would also be reliant on (but not depend on) the sampling rate you use and accuracy of voltage measurement when measuring it. IE the more samples you make in a given time period the more accurate the result.

Lets agree that at a point in time, for a period of time, each phase can be at 0V. So between that phase and 0V, then YES (no potential for work on that phase, at that point in time, between that phase and 0V).

However, if you see where the other two phases are at that point in time, then there is potential between that phase (currently at 0V) and either of the other two phases (+120degrees and -120degrees ... you can work out the voltage).

 

[Paul.M]

I hated motor calculations back at school, find them not too taxing now but its been a long day, im off for a drink :21:

 

[Ryan_Moore]

First draft of my 2-3 minute presentation.

Q. Find out what Voltage is used for the following:
a. Domestic electricity supply
b. Commercial/industrial electricity supply

Ans.
a. 230v single phase.
b. 400v 3 phase.

Q. Why is there a difference between these types of supply?

Ans.

Domestic- Because of the appliances, the most demanding of which being cooker, shower etc(requiring 6mm/10mm T&E 40A breaker) single phase, neutral and earth is sufficient for the demands of a domestic home.
However in a commercial or industrial environment a much greater voltage is required to power machines and equipment(such as one with a motor, the shutter in an electrical wholesalers) this therefore requires 2 phase, neutral and earth system, which allows the machine to draw upon 3 phases in order to gain the required voltage for it to operate. *graph handout and explanation*


note: I have a small question regarding the 3 phase graph, which is 3 sin graphs with a space of 6.4 ms between them(I think)
If you consider the graph and say you need 300v at time x, you can add the 3 values(one on each curve) to achieve this correct? However the single phase graph is just the sinx graph, so if at time x you only have a very small amount of volts the appliance wont work, so if my maths is correct, I am obviously missing something can anyone see what it is?
I understand it is very difficult to explain what I am talking about without a graph to see, tell me if I am not making sense and I will try an think of a better way to word it.

 

[topquark]

Here's something I produced a while ago. You'll need to smarten it up and ensure that the voltages and units of time are appropriate to your usage.
It should give you a start.

 

[topquark]

Have a look at the data under the graph that the graph is plotted from. Remember it's the current that we are interested in (ie a flow of electrons past a point) not the voltage. The voltage is simply there to overcome the resistance and produce the current that we need. For example to drive out motor.