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Q & A: mu-metal transformer core

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Most recent answer: 07/21/2013
Q:
Can mu-metal be used as an iron core? It is a soft iron, with a lot of amazing properties, a very high relative permeability, low coercive force, workable etc... But it has one problem, it saturates at low magnetic fields. How could this be solved?
- Moe (age 20)
Fort Collins,CO
A:

Mu-metal has another drawback for use as transformer cores. It is electrically conducting. That means that one needs to be careful about the geometry of the core to avoid losing energy to eddy currents. Still, by using suitably arranged strips, "laminations", that problem can be avoided.

The easy-saturation problem requires transformers in which the magnetic field never gets very large. With a big enough core cross-section, and lots of coils, one can still manage to get big magnetic flux and hence big EMF's. However, combining these constraints means that it's a nuisance to use mu-metal cores for most applications. They are used, however, for good transformers for low-level signals.

Mike W.


(published on 07/20/2013)

Follow-Up #1: mu-metal cores

Q:
If Mu-Metal was used as a core for an electromagnet, how could it possibly create huge EMFS? I believe it can potentially increase the magnetic field strength. I understand that I can avoid Mu-metal energy losses using laminations. My whole point, using Mu-Metal is an core, to amplify the magnetic field by the ten's of thousands(since its relative permeability is 10,000+). The saturation issue, I think it can be solved not only by limiting the external magnetic field, but also increasing the "size" of the mu-metal to handle more of the external B.
- Moe (age 20)
Fort Collins
A:

It sounds like we're in agreement. You may end up with excellent transformers, but they will be bulkier and more expensive than typical ones for routine use.

Mike W.


(published on 07/21/2013)

Follow-up on this answer.