Improving the efficiency of electric machines using ferrofluids

Ferrofluids have a growing importance in technical and medical applications since stable suspensions of magnetic nanoparticles in carrier fluids can be produced. The application of these strong paramagnetic fluids in electric machines by filling the air- gap between stator and rotor to increase the force in linear and the momentum in rotating machines offers an interesting possibility to improve efficiency and thus to save energy. Some calculations of this effect are presented here, including the method of magnetic circuits and field theory. Also, peripheral aspects such as fluid friction and thermal implications are discussed. Experimental verification by testing linear and rotating machines will confirm the positive results.