I have participated in an informal competition held by the electronics society at my uni to design a working high strength electromagnet using commodity off the shelf (COTS) components. The electromagnet is to be powered by any commonly available means with a maximum budget of =A3100. There are basically no rules to the competition except the budget and COTS requirement.
As far as I know, everyone else is working on the principle of a steady state electromagnet circuit. Typically, with the appropriate AC
-> DC voltage rectification circuit and the maximum current determined by the ampacity of the windings on the electromagnets. Alternatively, other people are working on electromagnets powered off batteries which obviously have limitations of internal resistance.
I think that since the measurements of the electromagnet's strength will be done over perhaps 30 seconds in the competition, the ampacity of the windings is not particularly relevant, i.e. it is possible to overload the current and rely on the thermal mass of the assembly to soak up the excess heat generated. Therefore, I would like to go for a circuit that can deliver a sustained, high current pulse to an external load.
I would like to try to build a circuit that charges up a capacitor bank in parallel and discharges it across the electromagnet in series. A Marx cascade seems to be of the sort I need but Marx cascades work with high voltage capacitors (to trigger breakdown of the spark junctions) and I think for a ~30 second sustained current, I will need capacitors with a high capacitance. Capacitors with a high capacitance tend to have a low voltage (I could find a 30F aluminium electrolytic capacitor on Farnell with a voltage of 2.3V)
As term has just started, please assume I just have knowledge of electronics from A-level physics.
Does anyone have any comments on my approach?
Will the maximum magnetic field strength I can achieve be entirely limited by the saturation of the core? I know the saturation of different ferromagnetic materials varies, but wouldn't the magnetic field be mostly generated by current flow rather than alignment of magnetic domains in the core?
Where can I source good materials like soft iron to build my core from (other than steel bolts)?
Do you have any suggestions on circuit topologies I could look into?
Thanks.
Jessie xx