Comparison of Induction Heaters

[some bloke]

TL;DR Summary

I have 2 induction heaters which are exhibiting different results when heating the same product. The 2 are different, having different sized coils, and I would like to work out the strength of the induced field in each of them (with a common item being heated) to establish whether they are actually even close to one another.
These are old machines which no-one really understands. This is my first step in trying to understand them better!

As the summary says:
I have 2 induction heaters which are exhibiting different results when heating the same product. The 2 are different, having different sized coils, and I would like to work out the strength of the induced field in each of them (with a common item being heated) to establish whether they are actually even close to one another.

The coil is a single coil, which is aligned perfectly flat. the item being heated is a ring shape, and in theory is a consistent distance from the coil. The coils both have a gap of circa 10mm where they enter and leave, forming the majority of a circle.

The information I am looking for is:

1: What data will I need to collect about the coils? I am assuming:

• Diameter of the coil
• thickness of the coil (they have a square cross section)
• wall thickness of the coil (they are pipes filled with cooling water) to then calculate;
• Cross sectional area of the coil.
• Distance from the coil to the ring to be heated (which is inside the coil, in the same orientation; 2 concentric loops)
• Power inputted into the coil
• Frequency should be the same as this is relevant to the material to be heated, would this affect the intensity difference if both coils are the same?

2: What formulae do I need to perform this comparison?

I have done some research but nothing seems to quite match what I am trying to establish!

Much Appreciated!

 

[Baluncore]

I would investigate...
The size and geometry of the coils, which will decide the coupling of the coil to the workpiece.
The frequency of the field, decides skin depth in the heated material.
The impedance matching of the generators to the coils, while the workpiece is present.
The forward power to the coil, while heating.

Are you able to swap the coils between the generators and matching networks?

 

[some bloke]

I can have a measure of the coils today and get their dimensions, that's no issue.
The frequency (from what I've been told) is the same (I will verify) as this is directly related to the item being heated, which is universal.
Not sure how to measure the impedance matching of the coils, I will need some guidance on that one.
Power to the coil I can get easily enough.

The machines are entirely different makes, so no, unfortunately I cannot swap the coils out.

Ultimately what I need are some equations which I can gather the information for, there's a lot about inductance but nothing about single coils which heat a concentric ring inside them.