Isolation Transformer-- Does Anybody Use One?

[pbbmorton]

Hi K_V_B

You are correct it is ac-dc-ac. The challenge with a charger/inverter is two fold. First the charger may not provided an isolated ground (as you mentioned some do). Second is the number of DC amps needed. If I am using it as the main supply for my AC (which is required for isolation) then I need 40 amps at 120 volts. This translates to a very large number of amps at 12 volts going into the inverter.

This is possible but the cost is high and is equivalent to units like the ABSopulse.

Now if your AC requirements are much smaller then it is much less problematic

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[K_V_B]

Originally Posted by pbbmorton

Hi K_V_B

You are correct it is ac-dc-ac. The challenge with a charger/inverter is two fold. First the charger may not provided an isolated ground (as you mentioned some do). Second is the number of DC amps needed. If I am using it as the main supply for my AC (which is required for isolation) then I need 40 amps at 120 volts. This translates to a very large number of amps at 12 volts going into the inverter.

40A at 120 V is a lot. That's still 20A at 240V which is more than my whole house had in The Netherlands. In Europe you'd probably need a three phase outlet. I understand this is a completely different challenge.
However on many boats peak loads are a lot higher than average loads, so a high power inverter can be coupled with a much lower power charger.


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[DotDun]

Originally Posted by K_V_B

40A at 120 V is a lot. That's still 20A at 240V which is more than my whole house had in The Netherlands. In Europe you'd probably need a three phase outlet. I understand this is a completely different challenge.
However on many boats peak loads are a lot higher than average loads, so a high power inverter can be coupled with a much lower power charger.


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Really? 4.8kva requires 3 phase in Europe? That doesn't sound right.

A typical 16a 230v/50hz outlet is 3.6kva.

My house has a 48kva entrance/panel.

[K_V_B]

Originally Posted by DotDun

Really? 4.8kva requires 3 phase in Europe? That doesn't sound right.

A typical 16a 230v/50hz outlet is 3.6kva.

My house has a 48kva entrance/panel.

A shore power outlet in a marina here is usually a blue CEE socket, and if it's done properly you might get 16a. But often it's less, which is why victron sells charger/inverter combis with power assist and a set table limit on the inputs.
But 16a is less than the 20a referred earlier. If you need more than 16a that you'll probably have to hook up to a beefier shore connection, and the next size up is usually a red CEE 400v/32a or 63a socket.

My house in Holland was an old house, and I could not switch on all appliances in the kitchen at the same time. Heating, cooking and hot water was all natural gas though, so electrical needs weren't that high, and thus the main circuit not the powerful.
Where I live now, in Switzerland the systems are different, as here houses where everything is electric are more common. 400V 3 phase sockets even exist in houses. I had one of these in my bathroom in my previous flat to run my washing machine off...





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[DotDun]

Originally Posted by K_V_B

A shore power outlet in a marina here is usually a blue CEE socket, and if it's done properly you might get 16a. But often it's less, which is why victron sells charger/inverter combis with power assist and a set table limit on the inputs.
But 16a is less than the 20a referred earlier. If you need more than 16a that you'll probably have to hook up to a beefier shore connection, and the next size up is usually a red CEE 400v/32a or 63a socket.

Amps are only half the story, it's all about power.

EU Marina 16A shorepower = 3.68kva
US Marina 30A shorepower = 3.6kva
US Marina 50A shorepower = 12kva

[GrowleyMonster]

Originally Posted by pbbmorton

ABSopulse has a transformer that handles both voltage and frequency. It is light weight and fairly compact.

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A transformer CANNOT change frequency. That would be impossible. The primary coil induces a voltage in the secondary coil. If the voltage in the primary switches polarity at 60hz, the output of the secondary will also be 60Hz. If the unit you speak of changes frequency, then it is not a transformer.

[pbbmorton]

GrowlyMonster

It is a transformer in name. It converts AC to DC to AC. Therefore it can and does convert both voltage and frequency.

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[pbbmorton]

Hi K_V_B,

Point is well taken it is a function the total kva needed. If you don't have any amp hungry appliances (AC, heaters, coffee makers) then it is an easy configuration. However, as soon as you start moving north of 1.8kva then the DC charger will require a good level of amps at 12 volts. Just wanted to point out one should do the math before purchasing the equipment.

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[GrowleyMonster]

Originally Posted by pbbmorton

GrowlyMonster

It is a transformer in name. It converts AC to DC to AC. Therefore it can and does convert both voltage and frequency.

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That's not a transformer. That's a converter. A transformer can't do that. A transformer is simply a core and some windings.

[captain58sailin]

This is the unit that came with my vessel, and it is big and heavy, (130 lbs). I think it still works, at least it hums when ever I plug in shore power. Sadly, I have not had time to investigate it for its different qualities.

[GrowleyMonster]

Originally Posted by captain58sailin

This is the unit that came with my vessel, and it is big and heavy, (130 lbs). I think it still works, at least it hums when ever I plug in shore power. Sadly, I have not had time to investigate it for its different qualities.

Wow looks serious. What is the KVA rating? I can't read the data plate.

[captain58sailin]

I tried blowing up the photo and I can't read the plate either, I'll have to check it out next time I get to the boat.