One of my favorite graduate classes, design of electro-mechanical systems focused on the topics of electricity & magnetism, and how these forces can be harnessed in electro-mechanical (EM) systems.
Lecturing the Class
Video snippet from a lecture my group and I gave to our class. Each group was asked to pick one EM concept or law and explain it to the class through a demonstration. Reproduced with permission from Dr. Buckner.
Parallel Path Magnetic Motor
One interesting project the class undertook was to evaluate the "Flynn Parallel Path Motor," a concept set forth online, whose authors claimed to have developed a device with a system efficiency of 130% (i.e. which doesn't abide by the first law of thermodynamics).
The devices basic concept uses permanent magnets (PMs) and windings of conductive wire energized with current to create magnetic flux, which can cause attraction between the central assembly (body) shown in the diagram above, and the two armatures separated from the body by small air gaps. If the armatures are stationary, and the magnetic force can be cycled so that it is attracting the top armature first, then the bottom, etc, the body could move linearly back and forth between them, producing work. (Click picture for more info)
I used equations and principles from lecture, as well as the freeware FEA code "FEMM" to analyze the authors' claims.
The FEMM working schematic. The materials are as follows: Cu (windings), Fe (body and plungers on each side), NdFeB (PMs).
FEMM flux density plot: Windings are energized & PMs are not included in this one. Magnetic flux flows through whole system counter-clockwise as one circuit, pulling in plungers on each side.
Windings de-activated & PMs only creating flux; both magnetic north poles facing towards top of graphic, so magnetic forces are opposing one another in the top iron body section, and take the path of least resistance through their respective plungers and back into the south pole of each magnet - pulling plungers in towards body on each side.
Entire FEMM flux density window shown, with darker colors representing higher density of magnetic flux (similar to stress concentrations in structural FEA codes such as ANSYS). Windings + PMs are working in this model, with 1 Amp running through windings. Some of the flux lines are being drawn from the right magnet to the left by the windings, although the power generated is not high enough to overcome most of the PM force.
When 10 Amps are applied, however, most of the magnetic flux is diverted towards the left plunger, increasing the force applied to it, while little work is being done to the right plunger. If the polarity of the current were switched, the flux would reverse and the right plunger would be pulled in to the body, while the left plunger would relax back to its original position.
Mathematical principles such as Kirkoff's Voltage Law (seen above) were used to validate FEMM models, to gain confidence in their validity.
The results of my analysis showed that while it would be theoretically possible to develop a machine that worked on the principles described, it would be impossible to achieve the claimed efficiency. As a best case scenario, under "ideal conditions" (no electrical losses, etc), even getting 100% efficiency would be very difficult.
Electrostatic Precipitator
Another project consisted of researching and a system currently used in industry that runs off a basic theory or equation of interest. I selected the electrostatic precipitator - a device used to clean dirty air produced by fossil fuel power plants.
The filtration process is as follows (this takes place in the exhaust phase of a typical power plant): through the use of an extremely high-voltage power source, the wires shown in the schematic are negatively charged to several thousand times the positive potential of the plates shown. In the first step, air laden with impurities passes into the device and over the negatively-charged wires. Because of the huge potential, the additional particles become negatively charged (ionized) as they travel across the wires. The air is then piped over the positively-charged plates, where the particles are strongly attracted to and become “stuck” to the plates, while the clean air continues through the other side of the precipitator.
These devices must be cleaned at regular intervals, and the captured particles can be processed further or disposed of in more environmentally-conscious ways, instead of depositing contaminants directly into the atmosphere.