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TECHNICAL BACKGROUND

Using an isolation transformer

The risk of corrosion may mean you do not wish to

fit your protective earth onto the hull of your boat.

However, to ensure your power system is safe you will

need to install an isolation transformer.

With an isolation transformer, the earth wire remains

within the power cable for safety reasons but is not

connected to the boat. The phase and the neutral of

the power connection will instead be connected to

the primary (shore) side of the transformer, which will

‘convert’ the voltage to the same or, if necessary, a

different voltage.

A new phase and neutral, galvanically separated from

the shore, will be available on the secondary (boat) side

of the transformer.

The neutral will be connected to the onboard protective

earth system, which will now have nothing to do,

electrically, with the protective earth of the power

connection. This way the connection between two

different metals (or two different types of the same

metal) is blocked, eliminating the risk of electrolytic

corrosion.

The neutral connection of the other power suppliers

onboard, such as the generator and the inverter, also

needs to be linked to the onboard protective earth

system. An earth leakage switch is prescribed by directive

ISO 13297 for recreational craft up to 24 metres. The

various options for earth leakage switches and isolation

monitoring are subject to this directive.

Consult an expert for more details.

By the proper use of an isolation transformer, galvanic corrosion can be avoided.

ISOLATION

TRANSFORMER

ISOLATION

TRANSFORMER

AC GROUND WIRE

NO CURRENT FLOW

GROUND

ALUMINIUM

STERNDRIVE

BRONZE AND STAINLESS

STEEL HARDWARE

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