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Safety and prevention of galvanic corrosion
A complete galvanic isolation between the ship and the shore network is achieved with an isolating transformer. It increases safety, eliminates the need for galvanic isolators and eliminates polarity problems.
Safety is taken for granted in onshore power grids. In the event of a short circuit or a ground fault, a fuse blows or a residual current device (GFCI) disconnects the circuit. The connection of the shore power ground wire to the metal parts of the vessel will cause galvanic corrosion as described below. If the earth conductor is omitted and only the live and neutral conductors are carried on board, all of the mentioned fuses on board are ineffective and there is no longer any short circuit protection.
Galvanic corrosion always occurs when two dissimilar metals that are electrically connected to each other are immersed in a conductive liquid (an electrolyte) such as sea water or polluted fresh water. In principle, the more galvanically active metal (the less noble) will corrode while the more noble is cathodically protected. The corrosion rate depends, among other things, on the type of
metals involved, the size of the surfaces involved or the water temperature.
It is a mistake to think that galvanic corrosion can only occur on aluminum or steel ships. In reality, it affects all ships as soon as metal parts such as the propeller and shaft, or metal hull penetrations come into contact with water and the ship is grounded via the shore connection. It may be tempting to do without the protective conductor for the shore connection: however, this is extremely dangerous for the people on board, since the protective devices then no longer respond (see above).
The best solution to prevent galvanic corrosion while maintaining all safety aspects is to install an isolation transformer. This ensures complete galvanic isolation from the land network. The shore power is on the primary winding and the on-board power supply on the secondary winding. The transmission ratio is of course 1:1. All safety systems of the on-board network work separately and independently of the shore power.
Soft start function or an inrush current limiter is a matter of course with the Victron isolating transformer so that problems with high inrush currents are avoided. It is recommended to connect the grounding of the secondary winding also when storing on land (e.g. in winter storage) in order to ensure maximum safety even then.
| isolation transformers | 7000W |
|
input voltage
|
230V |
| output voltage | 230V |
| frequency |
50/60Hz
|
| perfomance | 32A |
| soft start | YES |
|
transformer design
|
Toroidal core (low noise level, light weight) |
| entrance security | YES |
| CASING | |
| material & colour | aluminum blue (RAL 5012) |
|
protection class |
IP21 |
| weight | 28kg |
| Dimensions (H x W x D) |
362 x 258 x 218m
|
| STANDARDS | |
| protection class | VDE 0530 |