Making electromagnet and not burn the Magnet

Thread Starter

Amar Ram

Joined Dec 13, 2021
13
Hi All, I have made an electromagnet of using 1 mm diameter wire appx 60 turns.
here is the problem... i have 600W smps(computer power supply) and i want to use that to power my electromagnet.
On smps it shows 3.3V with 25A and 5V with 18A. If i connect my electromagnet to one of these terminals will my coil burn ? How to not burn my coils ?
 
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Audioguru again

Joined Oct 21, 2019
4,525
The 90W of heat will produce a temperature that depends on the size of the total surface area of the wire plus the electromagnet core at each end. If the electromagnet is small then it will get very hot.
 

MisterBill2

Joined Jan 23, 2018
11,582
The current flowing will depend on the resistance of the wire in the electromagnet. And the resistance of the wire will depend on it's length, which we do not know, and the resistance per foot, which can be looked up in a wire resistance table. So that will tell you how much current will flow, and the current multiplied by the voltage will tell you the watts of power dissipated in the coil. Calculating the heat that the coil can radiate will then allow you to determine the temperature rise, and that will allow you to decide if the coil will overheat, and if it will in fact burn up, which depends on the insulation material.
Of course, I have guessed that the wire is copper, and that it is insulated. Those are only guesses, and they may or not, be correct. But the process is the same no matter what the material is, except that for many metals and alloys there are no convenient wire resistance tables.

So the missing information is the length of the wire and the material of the wire.

My guess, based on only the information that you have given, is that indeed the wire will get very hot, based on the guess that the power supply will not shut down because of the overload.
 

Audioguru again

Joined Oct 21, 2019
4,525
He said the power supply is rated at 600W and the currents he measured produce 82.5W and 90W at two voltages.
The wire resistance increases at 90W because the heating is very high.
 

Reloadron

Joined Jan 15, 2015
6,523
During my much, much younger days, circa 1960 or so I made my first electro magnet. Using a large nail and maybe AWG 20 wire I wrapped it with I have no clue how many turns. Battery was an Eveready #6 I think, the ones with the screw terminals on top. With a new fresh battery I could pick up a few paper clips. Learning the math came years later. Batteries had a very short life, go figure.

I suggest you start reading about electro magnets and how they work. There is more to it, much more, than you may think.

Ron
 

Thread Starter

Amar Ram

Joined Dec 13, 2021
13
i understand sorry for my incomplete information. i will write all the information i have.
one electromagnet = 1 mm diameter copper wire having 60 turns on a 7cm diameter cylinder of 2 cm
I have two electromagnet both the coils are connected in series to each other. so if we add together that would 120 turns of 1mm copper wire on a 7cm diameter cylinder of 4 cm .

can i use either one of the power supply and not burn the magnet ?
want to run this magnet for like half an hour
 

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Thread Starter

Amar Ram

Joined Dec 13, 2021
13
The current flowing will depend on the resistance of the wire in the electromagnet. And the resistance of the wire will depend on it's length, which we do not know, and the resistance per foot, which can be looked up in a wire resistance table. So that will tell you how much current will flow, and the current multiplied by the voltage will tell you the watts of power dissipated in the coil. Calculating the heat that the coil can radiate will then allow you to determine the temperature rise, and that will allow you to decide if the coil will overheat, and if it will in fact burn up, which depends on the insulation material.
Of course, I have guessed that the wire is copper, and that it is insulated. Those are only guesses, and they may or not, be correct. But the process is the same no matter what the material is, except that for many metals and alloys there are no convenient wire resistance tables.

So the missing information is the length of the wire and the material of the wire.

My guess, based on only the information that you have given, is that indeed the wire will get very hot, based on the guess that the power supply will not shut down because of the overload.
i understand sorry for my incomplete information. i will write all the information i have.
one electromagnet = 1 mm diameter copper wire having 60 turns on a 7cm diameter cylinder of 2 cm
I have two electromagnet both the coils are connected in series to each other. so if we add together that would 120 turns of 1mm copper wire on a 7cm diameter cylinder of 4 cm .

can i use either one of the power supply and not burn the magnet ?
want to run this magnet for like half an hour


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Thread Starter

Amar Ram

Joined Dec 13, 2021
13
He said the power supply is rated at 600W and the currents he measured produce 82.5W and 90W at two voltages.
The wire resistance increases at 90W because the heating is very high.
i mean i can use either of the power supply does not matter as long as the electromagnet does not get very hot . of course due to resistance heat is dissipated that cannot be avoided
 

Audioguru again

Joined Oct 21, 2019
4,525
82.5W and 90W of heat are almost the same. They each will draw a higher current until it gets hot.

You said the coils are wound on cylinders. Usually an electromagnet is wound on a solid or laminated iron core.
A "U" shaped core produces higher magnetism if the parts it lifts touch both north and south poles.
 

MisterBill2

Joined Jan 23, 2018
11,582
We still do not know the length of the wire in the coil, 7 cm x 3.14x 60=23 x60 cm =1300cm=1.3 M approximately So the resistance will be about 17.4 ohms/1000M x(1.3/1000) M= not much resistance.
So the current will be limited by the supply, and all that power will be dissipated in the coils.
So the coils will get very hot indeed.
 

MisterBill2

Joined Jan 23, 2018
11,582
Please tell us what is the purpose of these electromagnet coils . Energised for half an hour, there must be a specific application in mind. Perhaps we can suggest an alternate approach. There is a whole lot of experience available in this site.
 

MaxHeadRoom

Joined Jul 18, 2013
24,991
@Amar Ram You need to find out the weight anticipated to be lifted and work back from there.
Usually DC powered magnets are very efficient when designed properly.
The largest I have worked on is on scrap yard cranes and these magnets operate at 100amps!
Down to small steel sheet material lifting of a around 8amps.
 

Audioguru again

Joined Oct 21, 2019
4,525
Amar Ram never said what is the core in the electromagnet so it is probably air or a small rusty nail then it barely produces any magnetism even at the extremely high current.
 
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