Electronics > Beginners
Calculating electromagnet – magnetism vs heat
perik:
Im making an electromagnet that will be more or less permanently turned on so I need to avoid heating problems. I have studied this a bit and came to the conclusion that:
the lower the gauge (AWG) (the thicker the wire) and the more turns around the core => the greater current it can handle and the lower the heat.
with this in mind I would have taken something like 500 turns around a 10 mm diameter screw, with pretty thick copperwire awg 20 (0.5 mm) or something similliar would be okey?
What do you say? Is there a way of calculating these heatingproblems before I decide the dimension and number of turns of my copperwire?
Kleinstein:
The thickness of the wire only changes from low voltage, high current to high voltage low current. The heat will be the same of the same amount of copper is used and the same field is created.
To reduce the heating, one should use the maximum amount of copper that fits in place and try to keep the magnetic field concentrated to where it is needed. Using an iron core of the right shape can help a lot. It is not only the iron inside but also the shape and return path outside.
radiolistener:
Did you tried to use neodymium magnets? It doesn't eat electricity, no heating. And it has very strength magnetic field :)
TimFox:
One method to improve heat removal from an electromagnet is to wind insulated tape instead of wire, but insulated wire is much easier to find. There are textbooks on electromagnet design that cover this. Otherwise, Kleinstein is correct: for a given fraction of a constant volume filled by copper, the same excitation (in ampere-turns) will need the same power, with higher voltage in thinner wire.
soldar:
An electromagnet needs more current to activate it than to hold it so it is common to reduce current when just holding.
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