# How much power is needed to melt aluminum using induction heating?

1. Feb 4, 2012

### mustafa01991

How much power is needed to be able to melt aluminum using induction heating?

So I have coil of copper wire around an aluminum cylinder.
The aluminum is NOT touching the copper wire.

the copper wire have a thickness of 0.5 cm.
d = 0.5cm
the copper wire is looped 20 times around.
N = 20
each loop is 10 cm wide
d= 10cm

m = 20g
Aluminum melting point is about 933 K
T = 933K

Feel free to change anything you like here like the mass and number of loops of the wire .. etc.

Is it possible to calculate this?

I looking for the formulas and how to use them to solve this, so i can tweak my design and recalculate.

2. Feb 4, 2012

### Staff: Mentor

Welcome to the PF.

Looks like you should be using copper tubing and liquid cooling of your coil:

http://en.wikipedia.org/wiki/Induction_heating

.

3. Feb 4, 2012

### mustafa01991

Thanks,
I've never built something like this before.
I didn't know that i will need cooling for the wire.
How hot will the copper get if don't cool it?
of course i need to know how much power i will run through it to calculate that.
so any idea about how much power is needed to melt aluminum?

Then I can work on the cooling method for it, if needed.
I live in Sweden so the temperature out side is about -10C now so is it cool enough for my experiment? :)

4. Feb 4, 2012

### Staff: Mentor

I only skimmed the wikipedia article, but it seemed to give some information about frequencies and powers to melt different things (I could be wrong). Have you been able to find any other power calculation resources with a Google search?

5. Feb 5, 2012

### technician

One thing you need to calculate is the energy needed to melt the aluminium.
The SHC of aluminium is roughly 1000 K/kgC so to raise the temp to melting point of about 700C for a 20g piece requires about 13000 to 14000 joules
The power needed depends on the time needed to supply this energy

6. Feb 14, 2012

### Greg-ulate

I found a really good explanation of many details required for an induction heater here

http://www.mindchallenger.com/inductionheater/

This guy goes into every aspect of the design. I want one!

edit: He says he made two, one 3kw and the other was 10kw and also levitated the work peice (awesome)

Last edited: Feb 14, 2012
7. Feb 14, 2012

### Mech_Engineer

For such a small sample, you'll probably only need a couple of KW, maybe less depending on how well insulated the aluminum is. You haven't mentioned anything about what kind of power supply you plan to use though; for aluminum your best bet would be an AC current in the hundred kHz range to help take advantage of the skin depth in the sample.

Do you have an understanding of the fundamentals behind different inductive heaters? The reason I ask is usually they're pumping hundreds of amps through the coil to get significant heating, and the coil in turn gets hot and must be cooled (water or maybe even LN2).

8. Feb 18, 2012

### Mike_In_Plano

There's a value termed work coil efficeincy which very dependent on the material. For example, the highest theoretical work coil efficeincy for copper is .5 since the work coil is made of the same material as the load. Thus, if your heating copper, you need forced cooling of the coil.
Aluminum is simular in that it is a non-magnetic material with a good conductivity. I don't recall off hand, but this number will likely be in the 55-60% range for aluminum.
For magnetic materials, you can get wonderful efficeincies since the field is typically confined to the surface by skin effect. Thus you do see some of these machines operating without cooling of the coils.