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!

"Steve Lusardi" wrote in news:fma6k9$ijg$00$1
@news.t-online.com:

People will not invest a dime to
correct a problem they do not understand. Stupidity has its just rewards.
Steve


This is absolutely true. Trying to explain it to them only makes them
angry. Unlike usenet, I keep it shut on the docks...(c;

On Feb 2, 6:23*am, Larry wrote:
"Steve Lusardi" wrote in news:fma6k9$ijg$00$1
@news.t-online.com:

People will not invest a dime to
correct a problem they do not understand. Stupidity has its just rewards..
Steve

This is absolutely true. *Trying to explain it to them only makes them
angry. *Unlike usenet, I keep it shut on the docks...(c;

Just a comment/question about GFCIs.

The typical North American GFCI operates when there is an unbalance
beteen the amount of AC flowing in the live and flowing in the neutral
wire. That unbalance may be due a potentially dangerous leakage to
ground (or in this case the boat/water) but not necessarily. That
unbalance operation is the reason that GFCIs are not recommneded for
use in domestic situations for fridges and freezers. You can come home
to a fridge of bad food!

Not that we should not use them and also understand how and why they
operate to provide safety, but it's almost as if the designation
'Ground Fault Current ...... ' is a misnomer. In Europe and elswhere
understand they are called RCDs.

I liked the discussion about isolation transformers. What sort of
wattage ratings would be typical; realizing that when the boat is at
the wharf unused there may be a minimum load, due to a little bit of
battery top up, maybe a fridge and a small bilge pump (itself often on
12 or 24 volt DC boat supply) that may cut in occasionally. Perhaps
intermittently 500 watts?????

We have on hand, for example several hefty transformers (basically one
to one ratio, with a few extra volt taps) each capable of at least 250
watts or more. Have often considered using them as isolation and minor
voltage adjustment devices. Also as mentioned, properly arranged,
transformer/transformers can be used to 'match' land voltages of
around 230v OR 115v to the boat.

Terry,
Your questions are right on target. In Germany, the main breaker must be
GFI. Therefore all loads within the distribution will be GF protected. In my
experience, there are only two types in Europe a .030 Amp and a .3 Amp
breaker. They do measure that load current matches return current. If there
is an imbalance, then there must be another return path to safety earth. In
Europe you will never see those in-line AC filters whose case is screwed to
the equipment frame exactly for that reason, as they bleed to frame(safety
earth). On a boat, they are very useful and if a more sensitive was
available, I would use that.

Isolation transformers can be made very elaborately or very inexpensively,
depending on the application. Most importantly is the way you connect the
safety earth wire from the shore outlet to your boat. I will not ever
connect it, but to do that is illegal. If you must connect it, it must
connect only to the transformer frame and NOT anywhere else. Your ship
ground is from the centertap of the secondary winding. To determine how
large the transformer should be, add all the loads that could be
simultaneously connected and add 20%.

Isolation transformer problems and there are a few. One, when connecting the
boat to the shore connection and the transformer is larger than 1KW, you
will very likely pop the ckt breaker for the feed because of inrush current.
Two, efficiency can be a big issue, so electric use can be significantly
higher. You cannot use an Auto Transformer for an isolation role. They are
the typical step down transformers used to reduce 220 volt power for 110
volts loads. Another problem that I encountered is that the ones that I
found were not suitable for marine use, even the ones so labeled.

Problem solutions: In rush can be contained by using a common incandescent
light bulb in series with the primary and after start, shorting past the
lamp. Two, if idle current is higher than you wish, make the primary winding
Ferro-resonant, by adding the appropriate capacitance in parallel with the
winding. If you want to know how, contact me off-line and I will tell you. I
decided to design and build my own, because I could not find one that met
all my requirements. I am very happy to state that my transformer met all my
requirements, is easy to use and very economical.

My requirements:
Accept input voltage between 100 Volts and 260 Volts (Japan = 100 V / UK =
260 Volts).
Adjustable output voltage = (end of dock low voltage syndrome)
Single phase only, output = 115 Volt secondary end to center tap and 230
Volt secondary end to end.
Power needed = 10 KW
Ferro Resonant primary selectable for both 50 Hz and 60 Hz.

Steve

"terry" wrote in message
...
On Feb 2, 6:23 am, Larry wrote:
"Steve Lusardi" wrote in news:fma6k9$ijg$00$1
@news.t-online.com:

People will not invest a dime to
correct a problem they do not understand. Stupidity has its just
rewards.
Steve

This is absolutely true. Trying to explain it to them only makes them
angry. Unlike usenet, I keep it shut on the docks...(c;

Just a comment/question about GFCIs.

The typical North American GFCI operates when there is an unbalance
beteen the amount of AC flowing in the live and flowing in the neutral
wire. That unbalance may be due a potentially dangerous leakage to
ground (or in this case the boat/water) but not necessarily. That
unbalance operation is the reason that GFCIs are not recommneded for
use in domestic situations for fridges and freezers. You can come home
to a fridge of bad food!

Not that we should not use them and also understand how and why they
operate to provide safety, but it's almost as if the designation
'Ground Fault Current ...... ' is a misnomer. In Europe and elswhere
understand they are called RCDs.

I liked the discussion about isolation transformers. What sort of
wattage ratings would be typical; realizing that when the boat is at
the wharf unused there may be a minimum load, due to a little bit of
battery top up, maybe a fridge and a small bilge pump (itself often on
12 or 24 volt DC boat supply) that may cut in occasionally. Perhaps
intermittently 500 watts?????

We have on hand, for example several hefty transformers (basically one
to one ratio, with a few extra volt taps) each capable of at least 250
watts or more. Have often considered using them as isolation and minor
voltage adjustment devices. Also as mentioned, properly arranged,
transformer/transformers can be used to 'match' land voltages of
around 230v OR 115v to the boat.