Galvanic Corrosion - Galvanic Isolator vs Isolation Transformer

There are many reasons for corrosion problems on; a bå and by corrosion we mean that metals on the boat is raised and started. This can happen on; a range of different metals but the most common are propellers, drives, rigging etc. which in the worst case can be taken up on a couple of weeks.

In this blog post we focus onå the galvanic currents that arise when connecting shore currents and how you can protect yourself against them.

Galvanic currents
Galvanic AC currents m is created between ground/pe on land vs ground/pe on board, i.e. when land ground meets the boat's ground/water. Galvanic DC current is created by due to different materials on board together with the boat's DC current.

A voltage difference (potential difference) exists between the boat's 230V ground, at the connection to shore, and the transformer station's ground. This can have several causes, often the resistance of the ground which gives rise to potential differences då uncontrolled currents flow in the ground.

The electric station is often a good distance away (km or miles), and the potential differences can be significant and it is not uncommon with 20-50V even if the most common are smaller differences below about 2V. This can firstly differ from one port to another, depending entirely on; for the countries.

We cannot affect the potential difference between the boat and the transformer station like this; what we need to do is to break the earth circuit between the bar and the shore contact, which is done with the help of a Galvanic Isolator or an Isolation Transformer.

Solving this by removing the incoming protective ground connection is absolutely not suitable or permitted, dark; personal protection äventured!

Galvanic Isolator
The galvanic isolator blocks low AC currents 

The galvanic isolator consists internally of two; diodes that are connected via an antiparallel way. When they are connected by this way the diodes let the current through on both sides but only if a certain voltage drop.

The isolator ä is installed directly behind the boat's 230 V socket. The forward voltage from the galvanic isolator is higher than the potential difference between metals. This means that this voltage will not allow conduction and the galvanic isolator as such will prevent all electrolyte current. However, if there is a (higher) fault voltage in the AC circuit, the diodes will conduct and the RCD will break the circuit.

See us range of Galvanic Isolators

Isolation transformer
Indispensable in professional marine power systems. Prevents electrolytic corrosion and serves above all as a guarantee for a safe electrical system. Toroid winding technology for quiet operation and high efficiency. The soft-start circuit ensures that the fuse does not trip when it is connected.

The isolation transformer separates ground, neutral and phase, which means that it also protects against Shocks, power spikes, etc. on the shore current side at the same time as it can withstand high potential differences, which creates complete protection. Some isolation transformers can also transform the current between 230/115V.

See our range of Isolation transformers.