Variable voltage transformer


#1

Do we have anything that will step up dc voltage by set amounts?


#2

We have DC power supplies that you can change the voltage on.


#3

Sounds like you’re looking for a dc to dc boost converter/switcher.
We don’t have one in the ELab


#4

@artg_dms , do we have what @TBJK is talking about? That might work.


#5

Yes, the ELab has DC pwr splys.
What are your voltage and current requirements?


#6

I am hoping to answer a question though empirical evidence. I have a piece of aluminum and I would like to see how the amperage changes with the voltage applied.


#7

Can you be more specific? Al will look like a short across the pwr sply. Run the voltage up and the current will go up with it and the pwr sply will immediately go into current limit mode to protect itself.


#8

If upping the voltage will increase the amperage through the aluminum rod then this answers my question.


#9

It will. Through aluminum and anything else. I wouldn’t recommend trying it with E-lab’s DC power supplies, but I don’t really hang out in there, so others can weigh in on that idea.


#10

By Ohm’s Law, increasing the voltage will increase the current through a conductor. Aluminum is a very good conductor.

I do not get what you are trying to prove.


#11

I’m trying to calculate the magnetic field generated by the flowing current. If I know the resistance, raise the voltage of a battery using a transformer, I can calculate the amperage and thus the magnetic field.


#12

That’s backwards. If you increase the voltage the amperage would go down given the same resistance. This is why 480 is better than 208/230 3 phase. You can get more power though the same size conductor. P=I x V


#13

Now I am really confused about your experiment. You made no mention about measuring a magnetic field.

To calculate it,

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magcur.html

Secondly, a transformer only works with alternating current. A battery puts out direct current.


#14

Thanks everyone for your answers. It looks like I need to do some more research.


#15

That applies for a constant power load, the P term in your equation. We’re talking about an aluminium rod, which mainly acts like a resistor.

For a resistor, raising the voltage across it will increase the current flowing through it, assuming the power supply can support the higher current. That’s Ohm’s Law, V=IR.


#16

Correct. An aluminum rod resistance will be very low resistance. I’d venture to bet that likely the leads or the power supply would burn (fuse or breaker) up before the rod would. At the diameter our power supplies could support, it would be wire & not rod. Additionally magnetically speaking, it would be extremely in-efficient for induced magnetism as opposed to iron/steel.

I’d like to see the results just out of curiosity. I thought it was pretty neat seeing a neodymium magnet slow down when dropped through an aluminum tube.


#17

In a straight current carrying rod, the material doesn’t matter much. The magnetic field is outside the conductor. Run the rod thru or near some iron ( but insulated from it ) - then you have concerns.


#18

variable transformer is called a Variac


#19

Yeah, here the material if the rod doesn’t effect the magnetic field created, the only factor is the permeability of the surrounding material, air in this case.

It’s not too difficult to use a compass and see this in action, while the compass will normally point north, when you run current through the straight wire the compass will begin to point tangent to the wire and keep that relation while its moved around. I’m not aware of any benefit of this effect (in the straight wire case of course), but iirc it does get factored in when designing high current bus runs, it will require extra bracing to prevent the busses from flexing under fault conditions.