You are correct Larry. I designed my own isolation transformer, because I
couldn't find one that met all my needs, but even building it myslf was not
inexpensive. My xformer is capable of both 50 and 60 Hz, is capable of
handling input power from 100 to 280 Volts. Input is phase and neutral, no
safety earth. The output has 5 voltage steps manually selectable. The output
winding is 230 volts with a center tapped neutral. Neutral is then tied to
ships earth along with both generator neutrals. Its rating is 10 KW. My
biggest problem was inrush current. This was resolved by employing a 300 W,
220 V light bulb in series with the primary and a 100 amp shunt around the
lamp. This works perfectly where the user starts the xformer with the shunt
disconnected and after secondary voltage is detected then engaging the
shunt. Primary idle current, with no secondary load and without ferro
resonant caps on the primary is .3 amps with 230 Volt input, so it is very
efficient. The xformer case measures 25" W, 15" H and 17" D and it weighs 94
Kgs. This size was necessary because the galley and hot water is all
electric. I carry only diesel fuel for safety reasons. I have to repeat
myself here. There is absolutely no way to protect your hull from other
boater's electrical faults if you connect shore safety earth to your boat.
Of course there are safety risks, but they can be mitigated. Here is an
interesting note. I designed two Isolation Transformers, this 10 KW model
and an automatic 5 KW model. They were shown at the London Boat Show a few
years back. I received "0" interest. People will not invest a dime to
correct a problem they do not understand. Stupidity has its just rewards.
Steve


"Larry" wrote in message
...
Andina Marie wrote in news:8810ac1d-6d25-48fb-b03f-
:

A Galvanic isolator consists of back to back diodes which still
provide an electrical path for AC current but block DC voltages up to
about 1 volt. So the ground protection for electrical faults is
retained but the small DC voltages that cause electrolysis are
blocked.

Assuming, of course, that nothing in the boat hooked to the AC line, like
AC compressors, fan motors, battery chargers, AC-powered refridgeration
and lighting has absolute NO LEAKAGE that will forward bias any of those
diodes.

This dirty little secret has trashed many boats I know of with diode
galvanic isolators. Even the slightest AC leakage, not even enough to
trip a good GFCI, forward biases the diodes in both directions 60 times a
second, allowing galvanic current to flow through the forward biased
diodes during every AC peak in the same direction.....completely negating
the flow-stop protection the diodes were supposed to provide.

Almost ANY motor sitting for years in the marine seawater environment has
some small leakage, more than enough to forward bias galvanic isolator
diodes without causing any noticable GFCI trips or any kind of shocking
experience because of the working circuit grounds. The DC galvanic
current flows right along with the leakage current to marina grounds and
to the other boats, completing the circuits.

The cure isn't cheap....but is cheaper than new propulsion, rudders,
posts, shafts, through hull fittings and labor...ISOLATION TRANSFORMERS
to take the boat completely out of the AC line loop. Now only
magnetically coupled to the power grid, the boat IS isolated....but not
cheaply with high profit diodes.

http://www.charlesindustries.com/main/iso_guard.html
http://www.defender.com/product.jsp?path=-1|328|303336&id=614209 $567
(120/240VAC 30A)
http://tinyurl.com/yus7an (West Marine but probably only 120VAC) $495

30A of isolated AC certified for boats. How much is a new shaft and
screw, installed?

It's a fair trade....

Shhhh.....don't tell anyone....You can also use it to boost 120VAC to
120VAC/240VAC to run the European equipment the boat came
with!.....shhhh. Did I say that?

Shhhh....you can also use it to run 120VAC outlets off 240VAC supplies
outside the USA, too, if you use the 120/240 models. They make great
boost drop transformers, properly breakered in/out.


Larry
--
As the price of Monopoly money rises, at some point it will equal
Federal Reserve Private Bank fake banknotes in value!