To reduce vibration and control heat in AC motors using ferrofluids.
Ferrofluid is a three component magnetic colloidal system consisting of subdomain magnetic particles, carrier liquid and surfacant. Ferrofluid behaves as a homogenous system even in an external Magnetic field. All the constituents of fluid range from 2-20 nm and fluid can offer good damping, sealing, heat transfer with reference to the applied field.
Basically Ferromagnetic materials are characterized by Curie temperature where Magnetization decreases as Temperature increases. Ferrofluid also has the same Curie temperature behavior. Fe3O4 based Ferrofluids have Curie temperature of 575 C (Ideal).
Major problem that occurs in an A.C. motor (I/P power) is due to heat gathered in poles. Ferrofluids, when placed on top every pole ensure good heat transfer. At an instant of high A.C. flux (peak voltage), intensive flux lines (reduce as moved away from pole) attract more fluid near the pole, and some are left behind. Heat conduction to the fluid takes place. Heating of particles causes the reduction in magnetization, so particle away from pole of comparatively higher magnetic moment gets attracted and particles with heat is moved away, causing Forced Heat Convection.
Convection of heat increases at high flux, low Curie temperature, high thermal conductivity, low viscosity, preferred volume/fraction of fluid.
Ferrofluids also play the role of acoustical mounts and soft vibrating materials rettored to acoustics. As these are held between rigid supports (outer cavity, platform and dynamic parts) reduces vibration by offering damping. As 50 expansions and compressions per second frequency are carried without any tension and dynamic action is lubricated, vibration is reduced.
Nanosized magnetic particles move randomly in the cavity by placement of closed coils. Current can be reduced in it.
Vaporization in fluid is less, so greasing is offered better than wax
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