Good day, I am designing a circuit which I can use to magnetize an alnico core to turn it into a permanent magnet. The alnico I am using has a saturation field (Hsat) of 50,000 A/m, and I would like to magnetize it with a 10ms pulse.

From my understanding, that means that for an alnico cylinder of length 5 cm, if I surround the alnico with 10 turns of coil, I will need to provide a current of:

\[ 50,000 [A/m] = \frac {NI} {L} \\ I = \frac{(50,000)(0.05)}{10} = 250A \]

My plan is to use a capacitor (eg. SCCZ1EB308SCB ), and discharge it through a coil of reasonably thick copper (resistance ~ 1.9 mOhm). Based on this resistance I would be required to charge the capacitor to ~0.5V

In my mind, the circuit would basically involve a DC power supply to charge the capacitor, then turning on some kind of transistor to short the cap through the coil for my pulse duration. I am unsure what other components I would need in terms of diodes etc, and was wondering if anyone might be able to describe what other considerations are needed in designing my circuit, or provide a diagram of something that might work.

Thanks for the assistance.

 

It would seem to be easier to switch if you used a 100 turn coil, which would only require 25A.

 

Two questions based on how much I ignore about this:

Why to limit the duration to 10us?

What if you repeat the process, several times? I recall doing so with a crude manual layout to magnetize common needles to implement a simple compass rose. To a certain extent it seemed to work.

 

Thank you for your replies. A little more context, I am trying to make a small scale electropermanent magnet, such as those used in scrapyards to pick up metal. Essentially, these consist of permanent magnet arrangements which can be turned "on" and "off" by an electromagnet. My aim is to do this as efficiently as possible

@crutschow
I have considered this also but I am trying to minimize the inductance for faster switch times

@atferrari
From what I have read about these systems, efficiency is inversely proportional to pulse duration, as full saturation is not necessarily required to get the benefits of the effect. From a paper I have read, highest efficiencies were seen at even lower pulse durations (10μs).

 

It's not necessary to perfectly duplicate the operating principles of a real 4-ton Electro-Magnet to
get perfectly adequate, and "realistic" performance out of a scaled-down Model version.
Which, BTW, will be much easier to power and control.
What You are talking about doing is actually a very complex machine.
It will take much more than a few Math Equations to actually get it to the point where it might work.
.
.
.

 

It's not necessary to perfectly duplicate the operating principles of a real 4-ton Electro-Magnet to
get perfectly adequate, and "realistic" performance out of a scaled-down Model version.
Which, BTW, will be much easier to power and control.
What You are talking about doing is actually a very complex machine.
It will take much more than a few Math Equations to actually get it to the point where it might work.
.
.
.

Yes I do agree that a smaller scale model could have different engineered qualities to it. I am setting up a simulation of the system in COMSOL at the moment and will come up with better parameters to aid with decision making, as I understand what I have presented so far may not be specific enough to request advice with circuit design.