DC/DC converter question

[Marcus]

Howdy!

DesignIng my first ROV at the moment and I am currently looking at different options for power supply. I want to make my ROV as cheap as possible and thick wires are expensive, so here is my idea:

- 16 gauge (1.5mm2) wire
- 24v/36v power supply
- 12v DC/DC converter

So, 16 gauge wire works fine up to about 10A. If I send 10A at 36v down my tether I should have about 27A at 12v after the converter (90% efficiency seems to be standard).

My question is: Do converters convert the voltage back to 36v on its way back or do I need to buy another converter or a wire that can handle about 30A to close the circuit?

Best regards

[martinw]

Hi Marcus,

If you have 10 amps of current going in at the top on a 24V/36V power supply you will have 10 amps coming back up the other way on the 0V (return) of the 24V/36V power supply.

http://en.wikipedia.org/wiki/Kirchhoff's_circuit_laws

You will have to be careful that your DC/DC converter can handle the swing in voltage, at no load it will see nearly 24V/36V, whereas at full load it will see 24V/36V minus the voltage drop through your umbilical.

http://en.wikipedia.org/wiki/Ohm's_law

Hope this helps.

Martin

[reHosea]

Marcus, you won't see an increase in the amperage on the output side of your converter. It will regulate the voltage, but not increase the output amerage. The 90% effeciancy is an indication of how much power is used (and wasted) by the converter itself, just to do it's job. To get an increase in amerage you will need to run 24/36 volts AC down to a step-down transformer, which can increase the amperage, (but it can also be very heavy) and then put a DC rectifier/regulator circuit on it's output. All of the information that martinw pointed out will also apply to this scenario as well. I hope this helps.

[martinw]

Hi Marcus,

And anyone else that may be interested for that matter, personally I think this is very good resource that can be used to understand the basics of electricity and electronics.

http://www.williamson-labs.com/

A picture paints a thousand words ........ so an animation must paint at least two thousand

Martin