Australian electrical system



We have a power system that is 240 volts single phase or 415 volts 3 phase.

The mains in the street have 4 wires, 3 x 240 volts (active) and a neutral.
Between each of the 240 volt wires is 415 volts and between the 240 volt
active and the neutral is 240 volts.

Most modern homes are supplied with an 80 amp 2 cable system IE 240 volts.

If the current draw is greater than that and no 3 phase motors are installed
then they can run 2 actives (phases) in and a neutral.

There are no transformers in these homes for the power supply, they just run
some things off one active and some things off the other active.

If the load is too great for this 2 phase set up or you have one or more 3
phase motors then they will connect up 3 phases to your home (3 actives and
a neutral) The power outlets are to be balanced over the 2 or 3 phases.

Power outlets in the homes are rated at 10 amps (2,400 watts) there are also
available 15 amp outlets (3,600 watts) and 20 amp outlets (4,800 watts)
although most homes do only have the 10 amp outlets. All outlets are
earthed, and the current regulations require the earth and neutral to be
joined in the fuse box.

The way the power outlets are configures is that a 10 plug will fit into a
10 amp, a 15 amp and 20 amp outlet, a 15 amp plug will fit into a 15 amp and
a 20 outlet while 20 amp plug will only fit into a 20 outlet.

There are 30 amp outlets, but there are very rare and in general and
equipment using a lot of power, is wired direct into an isolation switch and
not an outlet.

Here on the 240 volt systems the active is red or brown, the neutral is
black or blue and the earth is green and yellow (striped).


That is what we have for most homes, however in a few parts of the country
where there are quite some distances between the homes and power supplies
they do have an alternative system. it is 480 volts and only one cable, it
is called SWER (Single Wire Earth Return) at the home on a pole they mount a
transformer to supply 240 volts to that home.




Ø Thanks for explanation! However I work across USA, Europe and Ireland
trouble shooting

Ø Environmental test chambers (Climate change units) but I have never
come across as

Ø ridicules set up as that. Good luck my friend.

Just curios, what part of the set-up do you find ridicules?

Daniel who wants to know

“Grumpy said:
You have indicated that you have 4 wires' ( two hot one neutral and one
I can not figure out how are you getting 240 and 415 from same source???
The same way we get 120/208 here in the USA, the 2 legs are phased 120°
apart, not 180°, hence the 2 don’t fully add together. Stealing from

First, consider single-phase 120/240 service like you would find in a house.
the two hot wires are said to be 'in phase'.
Think of it this way. Imagine a ruler 12 inches long. Put your finger on the
six inch mark, the center. How far to each end? Six inches. Both ends are on
the same line, just in opposite directions. So if you go six inches one way,
and six inches the other way, the total distance is 12 inches.
120/240 volt systems are like that voltage-wise. The middle of the ruler is
the neutral, and each end is a hot wire. When one hot leg is going positive,
at the exact same time (that's the 'in phase' part) the other leg is going
negative. Same line only opposite directions, like our ruler. So the two 120
volt legs just add up to 240.
Now, here's the important part. Since one leg goes positive while the other
leg goes negative, they are said to be 180 degrees apart, 360 degrees making
up one complete AC cycle (2 X 180 = 360). In three phase power, there are,
not two, but THREE hot wires. Since there are three, they can no longer be
180 degrees apart. They are 120 degrees apart (3 X 120 = 360). So, when
phase A peaks, phase B has not yet peaked. it is at some intermediate
voltage between zero and maximum. The two phases cannot just be added up
because of this fact.
Back to our ruler. Break the ruler in half. bend the two halves so the ruler
is no longer straight (180 degrees) but bent at an angle of 120 degrees.
Draw a line from end to end. See how we have formed a triangle? See also
that the line we drew is not 12 inches long, but is shorter (the two ends
are closer together)? That's why the voltages in a three phase system do not
appear to add up.
Lets make our ruler 240 inches long. If we bend it into the 120 degree angle
and measure end-to-end, we will find the length to be about 208 inches, not
240! In a 120/208 three-phase system, each hot leg (phase) measures 120
volts to ground, BUT phase-to-phase measures 208 volts. This is true whether
you measure A to B, B to C, or C to A.
The math guys call this a vector sum. The vector is the angle at which the
phases are in relation to each other (120 degrees) and the sum is the
distance between the two bent ends (phases).
To figure the phase-to-phase voltage, multiply the phase-to-neutral voltage
by 1.73 (the square root of 3). Thus: 120 X 1.73 = 208, 277 X 1.73 = 480,
To figure the reverse, divide the phase-to-phase voltage by 1.73. Thus: 480
/ 1.73 = 277, 208 / 1.73 = 120, etc.
You trig people see how this relates to our triangle example using the
cosine rule.

It should be noted that the use of the term phase above, as in "phase to
phase" is not strictly correct, although a common usage. Each hot conductor
in a 3-phase system is correctly called a "line", so the correct terminology
would be "line to line", "line to neutral", etc.

Congoleum Breckenridge

It seems that we have misunderstanding out side on the pol 4 wires 415 Voltage
Ground, neutral and two hot or (Active),
how do you get 120 from that without transformer?
They don't use 120v in Australia.


"Grumpy" wrote in message

OK how do you get 220 from 415

Read my reply again we use 240 volts in Australia for household current and
we use 415 volts for commercial and domestic 3 phase motors.

We do not use 110, 120, or 400 volts here.

We do not have mains transformers in the houses.

We run in either 240 volts or 415 volts (2 or 3 phase) into the homes, the
extra phases only if require by load or for use of 3 phase motors.

By far the majority of homes only have 240 volts, as these days the mains
coming in to a home have 80 amp cables coming in.

So 80 amps x 240 volts gives you around 19200 watts, quite a bit of power,
almost 20 Kw.

I explained to you about the sub station transformers that give you 240
volts., read it again.

This 3 phase system is also used in most of Europe and UK with a slight
variation in voltages.

Again a list of overseas voltages.

If you do not understand then it is beyond you capabilities or are you just


From a previous note to Grumpy

The voltage is generated and here we use delta to wye transformers for power
supply, which delivers 415 volts 3 phase and 240 volts single phase.

Delta-wye transformer

In this case I guess they are quoting some US voltages, but the single phase
to 3 phase is not doubled.

//Phase to neutral Phase to phase

120 208

230 400\\





Ø Problem is here you have 480/3/50 to get 240 each leg, this is what I am
sking where are you

Ø getting 415 from?

You ask where the 415 volts comes from, well it comes from generators and
transformers. That is street and sub station transformers, as we do not have
main transformers in the homes.

You have been told the transformers are delta to wye (star) to produce 415
volts 3 phase and 240 volts single phase.

Delta-wye transformer

In this case I guess they are quoting some US voltages, but the single phase
to 3 phase is not doubled.

Phase to neutral Phase to phase

120 208

230 400


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