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High Voltage Transformer used to make Strong Magnet?
Posted by Shaun Honeycutt on 12/2/2005, 12:50 am -Shaun
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Re: High Voltage Transformer used to make Strong Magnet?
Posted by Bert on 12/2/2005, 8:06 am, in reply to "High Voltage Transformer used to make Strong Magnet?" Hello Shaun, An electromagnet develops a magnetic field that is proportional to the amount of current flow times the number of turns in the winding (called ampere-turns). In theory, it is possible to make a large electromagnet by using miles of small diameter wire, making lots of turns in the winding, and then driving the coil from a low current, high voltage source. This will result in a large number of ampere-turns. However, there are a number of problems with this approach. First, I suspect that all of the electromagnets you built as a kid ran off of batteries (or direct current). Your transformer outputs alternating current, so (unless you rectify the output) the magnetic field will want to reverse twice each cycle (100 - 120 times a second depending upon where you live). Also, the alternating magnetic field will cause a lot of eddy current heating if you tried to use a solid iron core. You would need to make your core from transformer laminations (thin sheets of specially alloyed silicon steel) or thin iron/steel wires that were individual insulated from one another. It is possible to use high voltage rectifiers to change the transformer's output from AC to DC, but this will add complexity and cost. Your high voltage transformer sounds like it may be a radar transformer, and it may not be internally "current limited". This means that it will likely overheat or blow the line circuit breaker unless you add external current limiting to keep the current to a safe value. Also, making an electromagnet that is capable of handling very high voltages is not a trivial task. High voltage coils need to either be immersed in oil or vacuum impregnated with insulating materials to exclude any air. This is essential to prevent the formation of corona - corona will otherwise quickly destroy the insulation on the winding. Finally, you can simply and safely make a very powerful electromagnet by using thicker wire powered from a low voltage DC source such as a 12 volt DC power supply or lead acid gel cell. Using a higher current and fewer turns will still give you a high ampere-turn product. Do you REALLY want to play with an electromagnet that has 30 kV RMS (over 42 kV peaks) sizzling on its windings? Good luck and play safely, Bert
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