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Peter Kennedy has been in  business since 1991 designing, installing and servicing marine electrical systems. The purpose of this blog is to offer support to both professional installers and  do-it-yourself boat owners who wish to undertake this work themselves.

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Peter Kennedy has been in  business since 1991 designing, installing and servicing marine electrical systems. The purpose of this blog is to offer support to both professional installers and  do-it-yourself boat owners who wish to undertake this work themselves.

Generating a 120/240 Volt split phase power supply from an inverter

Posted by Peter Kennedy on 3/7/2019 to Victron MultiPlus and Quatro
There are a couple of ways to set up a split phase 120/240 volt system using an inverter.  The drawing below shows the conventional way where two inverters are paired together in a back to back configuration to work in sync and produce 120/240 volts.  This works fine as long as you have inverters that can be ganged together like this to work in sync.  The main disadvantage of this arrangement is   1) You need two inverters and   2) You can only draw from inverter one to power leg A and inverter two to power Leg B.   If leg B has a lot of load and leg A has none there is no way to get the other inverter to help out, it just sits there.

Twin inverters

There is an alternative way of doing this that is more versatile.  It uses a 240 volt inverter in combination with an Autotransformer.  This is what it looks like.  

Autotransformer with 240V inverter

In this arrangement the Autotransformer can split the 240 volt output of the inverter into two legs and balance the loads between the legs in such a way that you can have all the load on one leg if you want.  Its a much better setup with greater functionality and it allows you to use the inverter to its full potential.

All Victron VE Bus Inverters, Multi Plus Inverter Chargers and Quattros are available in 230 volt 50 Hz and with a simple software tweak can be converted over to 240 Volt 60 Hz.  They are available for 12,24 or 48 volts DC and in outputs up to 15 KVA.  Take a look at our Inverter Charger page for more details.  If you dont see a 230 volt version just ask, we dont have them all listed on the site.  The Autotransformer is relatively inexpensive and comes in two sizes, 32 Amps and 100 Amps

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Comments

2 Comments

Andrew Addison
Date: 4/27/2019
Reply
Hi Peter, Does this give me a way to provide the same 50A supply that I get from the shore power and generator? I currently have an inverter that can provide 30A on each leg but it drives me nuts that I have to be careful what I run before popping the breakers, whereas on shore power I can run the lot - stove, AC, microwave, etc - without worrying. It would be great to be able to run the stove to boil the kettle without having to switch on the generator. Clearly the battery bank needs to be fairly large - we currently have 880ah of lead acid batteries but it is looking like when they need replacing lithiums are going to be a sensible price. I've been told that getting a separate charger to the inverter makes more sense especially if we take the boat from the US to the UK/Europe - is that still the case or can the inverter chargers cope with different input voltage/freq? Cheers, Andrew
Peter Kennedy
Date: 6/17/2019
Reply
This Autotransformer is for a special purpose only as described above. If you read the manual there are a few other specialized applications. It isnt intended for use to change the voltage of shore power for international voyages and it certainly isnt an isolation transformer.. In some applications it doesnt really behave as a transformer at all because the two input wires go straight through to two of the three output wires. Victron have two transformers that can be used for international voltage conversion, 120 to 230 volts and vice versa. They are both limited to 32 Amps at 120 volts, 16 Amps at 230 volts. Neither convert the frequency. One version has automatic voltage detect for the input and a predermined user adjusted output voltage. The other version has to be set up manually. You will find both of these in our SHORE POWER > TRANSFORMERS section.

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