"Sparks" wrote in message ...

You could use a step down tranni' as a supressed earth to give a decent
neutral potential to supply the house circuits, and reduce the fuel
consumption of the generator into the bargain, using the transformer
looped
from phase to primary winding, then on to the secondary winding and out
to
earth. But as I say, both connections on an AC genny are phase, so it
literally doesn't have a neutral and is dangerous if used with
capacitative
loads.

You could ruin your tele' or damage any IF filters in other appliances
if
they rely on a phase to neutral supply, so it then becomes a very
expensive
installation if you have replace everything. The grid itself is
literally
phase and earth connections, but an AC generator is alternating phase /
phase supply.

I have a "power conditioner" rated at 40A - this contains a bloody great
transformer
(it must weigh about 50KG!)

It is not a step-down transformer, as the generator's output is the
voltage
I require!

Excuse my ignorance, but how is a petrol generator different to the output
of the grid?
I was under the impression the grid's Neutral was connected to earth, so
they only need to run live cables - this being the reason people got
electrocuted - they touch the live, and this shorts to earth, or neutral!

We install isolation transformers in bathrooms, and on building sites, so
the neutral is no longer connected to earth, making electrocution
impossible
unless you touch both live and neutral together - surely a generator is
safer then the grid, due to the neutral/earth isolation?

Please correct me if I am wrong, it is just how it seems to work from my
point of view!



You're right about the grid supply being phase and neutral, but a generator
supply is phase / phase with no earth / neutral potential. This means that
any appliances you have in the house may not be switched off when you think
they are and may actually continue to heat even if you think they are
switched off.

Do this simple test with a meter.

Set your meter to the appropriate setting to take the AC Voltage of your
supply.

Place one test probe on the earth connection of your mains supply and the
other probe on the neutral connection. You should see that the test meter
doesn't show any or shows very, very little voltage flow. If anything does
show, then it more than likely it has no current large enough to run
anything other than a small torch bulb and would dissappear if any large
load were connected across them.

Now, keeping one probe on the earth terminal, place the other probe on the
live connection. Your meter should now be showing the full supply voltage
of your system and it will carry a very large current potential. This
allows you to run all your appliances.

Next, go and start up your generator and carry out the same tests as above.
You should see that both, what are known as live and neutral, are showing
half of the rated voltage to earth, that it is said to supply. This is
because an AC generator works on the principle of each phase being 180
degrees out of phase with the other, therefore, it supplies + phase on one
side and - phase on the other, and the phases alternate between supplying +
and - of the supply at the rated hertz frequency of the generator.

There is no neutral / earth potential from a generator and it must be
properly connected to the AC supply system, when and if the load has any
capacitative loads, i.e. televisions, IF filters in appliances, etc. etc.
Please be careful if you intend to use a generator as a backup supply for
your domestic system.

An isolation transfomer only works by bringing in different tapps on a
transfomer to supply an increasing current load. It is nothing fancy and
sure won't help in the situation of supplying a domestic AC electrical
supply.


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