Low shore power voltage

It sure sounds like you have 2 phases out of 3, which shouldn't be used, but I've seen many marina's do it. Have you tried a 2-30amp to 50amp splitter and tested what the voltage is there? You also need to find the end of the shorepower cord (just follow it out of the glenndenning storage bin) and test what voltage is there. I'm more willing to bet it's on the marina's side, and the marina could even have a poor grounding issue or just a supply issue. You cannot go wrong with a voltage booster........

By definition, all transformers are "isolation transformers". The input wires never connect to the output wires. The electrons are moved across coils or plates by the magnetic fields. Its the ratio of input coils or plates to the output coils or plates that determines if their is a voltage drop or gain. If the ratio is the same the only reason for that is "isolation" of the input current from the output current, without a voltage increase or decrease.

The type of transformer that may be applicable to the issue under discussion (if the supply voltage is low) is a "buck-boost" transformer and like many other transformers, will most certainly have inputs that are electrically connected the output.

Low voltage, dry-type, buck-boost distribution transformer

The "dealing with" comment is in reference to the apparent fact that no one seems to know what the voltage on the dock or at the end of the shorepower cable really is. There has been no post stating that the voltage has been measured anywhere. It has been stated that a panel meter on the boat indicates low voltage but that reading has not been confirmed as accurate.

Until someone who knows what they are doing actually puts a meter on the pedestal, the shore power cord, and the switchboard, no one here, including me, has a clue what is going on with that boat or the marina where it lies.

Quite frankly, at this point I would just get a marine electrician on board. In an hour or two, he should be able to tell you where you stand.

"Quite frankly, at this point I would just get a marine electrician on board."

Finally ... 50 posts later!

If you just point him in the direction of where the glenndenning shorepower storage bins are, and the panel, it should take an hour or two to figure out what's going on. I feel it's on the dock end. It sounds to me like the marina is using 3 phase that they split up, and they should have a transformer and most likely the transformer is bad.......but without being there, meter in hand, it's just an assumption and all of us have idea's but are pissing in the wind. Whereas an hour or two of time and a multimeter will tell the entire tale.

If it's not on the marina side, it sounds like it's either the shorepower cord or end, or a bad ground.

From your link:

Buck-boost:
The name of a
standard, single-phase, two-winding
transformer application with the
low voltage secondary windings
connected as an autotransformer
for boosting (increasing) or bucking
(decreasing) voltages in small
amounts. Applications can either
be single-phase or three-phase



Autotransformer:
A transformer in
which part of the winding is common
to both the primary and the secondary
circuits.


The auto transformer has windings or plates common to the primary & secondary sides.

Common windings does not mean connected or (tapped) winding, IIRC. This is the part that changes the ratio to boost or buck the voltage.

I'll have to meter one to see if I can read a circuit (Polarity) from the primary to secondary sides of a non-energized one.

Why not just look at the wiring diagrams provided in the link I posted?

http://www.eaton.com/ecm/idcplg?Idc...veAs=0&Rendition=Primary&dDocName=TD00904001E

In my above post I was thinking Continuity but typed polarity. If a mod can make the change this post can be deleted.

Marmont your right on the auto transformer. but I didn't realize they are part of the buck/boost transformers. I looked for a diagram ,must have opened every pdf except the correct one.

But why not install isolation ones? cost is probably a factor.

Danger, Will Robinson!

Not all transformers isolate their primary from the secondary side!
Enter the autotransformer. Yes, that means that you can electrocute yourself if you touch the phase (aka the hot lead) on the output on these.

[Autotransformers are often used where isolation is not required because they use significantly less copper. They are smaller, lighter and cheaper. And guess what, a look at the technical data for the low voltage, dry-type, buck-boost distribution transformer linked by Marmot shows that they are autotransformers.]

Normal transformers indeed isolate primary from secondary side. But depending on the application stuff gets tied together again, say connecting neutral to the same ground.

Isolation transformers have a specific application, they are used to break ground connections. Characteristics are:
- Usually the input and output voltage are the same. They may include additional taps to compensate for to low (or high) input voltages for situations like the marina we are talking about in this thread. But those are only fringe benefits, not the reason to use one in the first place.
- They usually have a specified (and often proven) isolation voltage between primary and secondary windings. The actual requirement is depends on the application and can be found in the regulations. IIRC for medical equipment its exceeding 5000V. "Frying patients is bad, m'kay."


Why would you want to break the ground connection on a boat in the first place? Galvanic corrosion. [Tomorrows posting, too late today.]
Simply breaking the ground connection is bad™ for several reasons. It renders protective earthing moot, the missing potential equalization is an electrical hazard, etc.

Thus the use of an isolation transformer which allows to do such a thing safely.
But it is heavy. Expensive too.

So the marine industry galvanic isolator (aka ZincSaver) which is NOT an isolation transformer, nor any other type of transformer, was invented.
It is installed into the ground connection and basically consists of four diodes. Two anti-parallel diodes and two of those pairs in series. This adds a burden of about 1.4V to the ground connection.
AC current can still flow but the galvanic voltage between your ship and marina installation connected via the ground wire is usually not high enough, thus galvanic corrosion does not happen. (At least not that way.)

Galvanic isolators are quite robust but must be sized correctly and have to be protected by fuses and RCD.


I wanted to write more but is late and the misconception about transformers is too dangerous to let it stand.
Even in 120V country where the risk of lasting damage is a bit lower than elsewhere.

for starters...........

7 Function Multimeter