Ampage formula when using an inverter, HELP!

[emmitdb]

Greetings,

I understand the formula for finding the ampage of a product by dividing the volts into the watts but I would like to know what happens when the product is converted from one voltage to another.

Please let me explain.

If I have a flourescent tube that is mains powered at 230volts with a nominal wattage of say 13watts then by dividing the volts into the watts I get an ampage of 0.056 amps.

What would happen if I powered that same tube via an inverter from my caravan battery to provide the 230volts.

Sorry if I am asking the obvious but it ain't obvious to me!

 

[gary]

Ohms law works the same regardless, a 13w load at 12v equals just over 1amp.

The problem with the inverter though is internal losses so output at 230v is not directly proportionate to the input at 12v

So all depends then on how well the inverter is designed and manufactured? but that's another law?!

 

[emmitdb]

Ohms law works the same regardless, a 13w load at 12v equals just over 1amp.

The problem with the inverter though is internal losses so output at 230v is not directly proportionate to the input at 12v

So all depends then on how well the inverter is designed and manufactured? but that's another law?!

Gary,

Thank you.

Regards

del

 

[RonD]

Gary,

Thank you.

Regards

del

Del,

Just to add to Gary's comments, an inverter will still take current from a 12v battery even if it's not providing any power at 230v. Nothing is 100% efficient and an inverter is no exeption.

Ron

 

[ChrisUK]

I would take the mains rated wattage and divide by 12 to get the current into the inverter from the battery, then add at least 20% for the losses in the inverter.

 

[JeremyClarksson]

You will draw slightly more than expected because of the inefficiencies of using and connecting a converter.

If you already know the current rating at 240V multiply by 20 - most transformers have a max current draw on their plate, and that is not a bad thing to use for an estimate.

Before I get picked up on using 240v, that is what we get in the UK the 230v is a European standard with tolerances to include the 240v system we have had in the UK for years, nothing has been changed in the UK infrastructure to change that.