Power supply question - my kid is making a super-magnet !! Yeah, non audio but electrical.!

chapps

Well-Known Member
Many of you guys here are very well versed in basic electronics and some are experts. Right? Can any of you chat with my son to figure out this issue? Part of his school science project to draw out 50nm magnetic nano particles.

So my son blew his power regulator trying to make a home magnet where the temp went beyond 200*C (Celsius), With that headline here is whats going on:

1. ~1000 rounds of wire around a metal core.
2. Currents easily pushing 10A. He needs to go to 30A. This makes the wire real real hot ! ((So we are rigging a holder for dry ice (-110*C) to cool the coil.........that;s in the works.))
3, The heat dropped the resistance and the current surge draw blew the regulator of my power supply.

Q1. Can I figure out what in the regulator has blown ? It is a board, so is this replaceable?
Q2. What kind of power supply would be best for this stunt?
Q3. Is the heat avoidable?

I appreciate any input, since I am lost as to where to point him!
 
OP... Before few years I need one power supply with minimum 20A on output and with 12V for my project. At the end I bought one 12V/30A switching power supply from ebay and till today it work perfect as first day. You can to find on ebay switching power supply with 12V/50A or 24V/50A. 12V/50A cost about $50 and 24V/50A cost about 55-60$. You can also to find swithing power supply at 5V and 48V with same range on Amperes.
 
@FileFixer The flat resistance of the magnet is 4 ohms, once the induction resistance drops to 0. So to drive it at 10A at room temperature I'm would need at least a 40V 10A power supply without some sort of step up converter. However, as the temperature of the magnet increases, the resistance increases very quickly, so the increased current draw blew the 12A buck boost converter/regulator I was using. (I was using the buck boost converter to vary the current output from my power supply so I could vary the field strength of my magnet.) I can drop the resistance to very low by cooling the coil with dry ice, but in case I don't have dry ice on hand I would like some sort of variable output system that can drive the magnet at room temperature.

@eiraved Right now, I'm using a 12V 30A power supply. However, the buck boost converter I was using was only rated for about 12A. One of my friends suggested using his DC variac as a variable power supply, would that work?
 
DC variac can work but it also depends what is max A on output, you need minimum 15A to be safe.
48V/20A for $62 on ebay. You dont need any buck boost converter with this...
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@eiraved Right now, I'm using a 12V 30A power supply. However, the buck boost converter I was using was only rated for about 12A. One of my friends suggested using his DC variac as a variable power supply, would that work?
Absolutely. What FileFixer said.
 
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Ok, never mind about the variac, he said it's actually an AC variac and I would need a bridge rectifier to convert it to DC, which I don't have. Any other options?
 
What is your target magnetic field strength? What is the magnetic permeability of the core? How did you calculate the need for 30 amps of current?
 
@I LIKE MUSIC 30A came from my dad (the OP)!! :rolleyes: Around 10A (max up to 15A) will give me a field strength of around 1T using a permeability of 0.00001 H/m. That should meet what I need. Any extra current would be a nice bonus!

@FileFixer Thanks for the suggestion, that should work as a supply but I need a way to control the voltage output. The V/A ouputs seem good.

EDIT: The heating still has to be offset with severe cooling.
 
I don't know the dimensions of your solenoid, but a guess for a quick back of the envelope calculation looks like that should get you there.

Make sure that all of your connects are very secure. A quick reduction or interruption of the current may cause a counter emf voltage spike. With that amount of inductance it could be healthy spike.

I might put a reverse polarity diode across the coil.

Good luck with your project.
 
Could you use a car battery as the power source?
I’d think you’d want to have a circuit breaker in the circuit.
 
Or get a good N52 neodymium magnet..........and try not to break my fingers ! Something with 300lb pull force!

Some of these can go to 0.7 T at the surface.
 
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