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mestafin avatar image
mestafin asked

Isolation Transformer Overvoltage

I have a Victron 230V / 3600W isolation transformer connected to a Quattro on my boat.

The isolation transformer regularly delivers 250V - 259V AC due to the 1:1.05 winding ratio.

To protect the AC devices on the boat, the Quattro is configured to disconnect from the grid above 254V and reconnect again when the grid voltage dropped to 250V.

This happens multiple times per day and the Quattro can be disconnected for hours.

I understand the reason for the 1:1.05 voltage boost, but in my home marina (the Netherlands), the voltage supply is very good and does not need the voltage boost.


From the documentation, there does not seem to be extra taps on the transformer to bypass the voltage boost.

Any ideas on how to fix or mitigate this problem?

Isolation Tranformer
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1 Answer
pwfarnell avatar image
pwfarnell answered ·

There are quite a few threads on here about this if you search. These say that you can swap the primary and secondary coils around so you get a 1:0.95 ratio at idle but 1:0.89 or slightly lower under load. They also state that this is a service centre modification. Nobody has posted any details of how this is done to allow diy swapping of the coils or any results of having done it.

In my marina, I get the same issue but live with it because we are rarely hooked up having a good solar setup.

The downside to changing around is if you hook up in other locations when you travel and find yourself in a low voltage marina.

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