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The force balance of the magnetic bearing is maintained near the point of metastable equilibrium where complete stabilization can be obtained with the application of weak restoring forces, either from a mechanical bearing or from the action of residual eddy currents in a snubber bearing. The bearing includes a means for automatically adjusting the magnetic parameters of the stationary bearing element with respect to the rotatable bearing element to provide axial stability, such that the force balance of the self-adjusting magnetic bearing is maintained near the point of metastable equilibrium. Means are provided for varying the relative electromagnetic contributions in the different sectors to maintain stability of rotor positioning with minimized electric power.

Dolor Neuropático Pdf

U.S. Pat. No. 3,877,761 provides a contact-free bearing system for radially supporting a rotor, rotatable at high speed, with respect to a stationary member. In FIG. 3, the rotating eddy current exciter 72 exerts a repelling force (in opposition to the attractive force of the upper poles) on the stationary eddy current plate 68. The design is made such that the net resultant of the attraction and of the repulsion, taken together with the weight that is being supported (e.g., the rotor of an electromechanical battery) is a state of vertical force equilibrium.

Fisioterapia Neurológica

FIG. 5 shows an improved version of a type of modular electromechanical battery. When the bearings are used in an evacuated region, as in most electromechanical battery (EMB) designs, the heat balance that determines the temperature of the eddy current plate 68 is primarily a balance between eddy current heating and radiation losses (assuming that the support rods 62 and 64 are made of a low conductivity material such as stainless steel). This change in bearing design results in an overall design that permits the simplification of all the elements of the E-M battery that operate within the vacuum housing. Dolor de espalda parte baja derecha . In this way the damper accomplishes its objective; the damping of transverse vibrations with a minimum of undesirable effects. One type includes a self-adjusting magnetic bearing system in which magnetic fields arising from a rotating multi-polar element inside the chamber (co-located with the attracted pole assembly) produce a torque on a conducting surface above the chamber wall.

NáUsea Y VóMito Postoperatorio En CirugíA Ambulatoria In such systems it is common to use what are called “eddy-current dampers” in which a stationary conducting plate (copper, for example) is located close to the surface of a rotating annular permanent magnet. Referring to FIG. 5, it can be seen that the upper, non-rotating, element 90 of the magnetic bearing exerts its attractive force through the surface of the vacuum housing 92 (which may be made of insulating material or stainless steel) on the lower, rotating element 94. This (lower) element 94 can be of very simple form, consisting only of an appropriately shaped iron (or ceramic ferrite) pole, for example as shown on the drawing, possibly with auxiliary elements. Eddy currents thus generated will also generate a torque in the conducting plate, with a magnitude that is proportional to the force of repulsion.

The eddy current damper plate 80 may have a plurality of concentric conducting rings separated by material that has a conductivity that is less than that of said conducting rings. Stationary bearing element 50 comprises a cup shaped element 52 made of magnetically conducting material such as iron. Detached pole assembly 30 is used as a sensor for vertical displacements away from equilibrium of the bearing element 34 that supports the rotor. This much-simplified version is particularly well suited for stationary applications, where low cost, high reliability, and long service life are the critical parameters. If the springs are reasonably compliant, this sensing might be accomplished simply through the change in electrical capacity between the detached pole assembly 30 and its surroundings (the stationary bearing element 36, and/or a chamber wall). The torque is used to actuate rotatable assembly 24 to rotate about drive screw 22 to vary the position of the magnetic shunt pair 26 within the permanent-magnet-excited magnetic bearing.

This shunt then weakens (or strengthens) the force exerted by the bearing until it approaches a position of force equilibrium, i.e. A model of this damper has been constructed, tested and found to perform in a far superior manner to conventional eddy-current dampers. When conventional eddy-current dampers are employed, deleterious side-effects may appear, including loss-producing torques, that absorb energy from the rotor. Alternatively, an ac-activated circuit that senses the reluctance of the magnetic circuit comprised of the lower and upper poles could be employed, as a part of an electrical servo system that would maintain vertical stability.

Alternatively, if the supporting spring elements are very stiff in the axial direction then the change in force on the detached pole assembly 30 associated with a vertical displacement of the lower bearing element 34 could be sensed by resistive-type strain gauge elements. It may turn out to be advantageous to have a similar (but not necessarily identical) bearing assembly located lower down on the rotor, so that the position of force equilibrium is one that is determined by the vector sum of both bearing forces, taken together with the supported mass. The self-adjusting magnetic bearing shown in FIG. The means for automatically adjusting the magnetic parameters comprise a thermostat element 65 supported between the eddy current plate 68 and the non-magnetic metallic material 66 of cup shaped element 54. Dolor de espalda me despierta . The eddy current exciter 72 may be a slotted pole or a Halbach array, as shown in FIGS.

The magnetic bearings of the present invention are stable (strongly restoring) for radial displacements, but must be stabilized vertically (axially). The system described herein is much simpler to implement, and reliable compared to most “active” magnetic bearings (using sensors and electronic servo circuits) that this level of instability should be ignorable as compared to the economic advantage that is gained. In this action the eddy current-driven actuator performs a similar function to the electronic feedback circuits used in “active” magnetic bearings to maintain the bearing at the point of metastable equilibrium. This change may result in a vertical displacement of that element, acting against supporting spring-like elements.

Dolor Neuropático Central

Element 82 has field lines that intersect the eddy current damper plate 80. In another embodiment, eddy current damper plate 80 is fixedly attached to a stationary bearing element, and annular permanent magnet element 82 is fixedly attached to a rotatable bearing element. 1, an annular stationary bearing element 10 comprising annular iron pole pieces 12 is attached to a support structure (not shown). A second embodiment, shown in the cross-sectional view of FIG.

A second pair of slotted pole pieces or a planar Halbach array pair are attached with a reversing gear to the shunt pair 26. In operation, as eddy current plate 20 approaches slotted pole pair 28, a torque is induced which drives the shunt pair 26 down to a position closer to annular pole pieces 12, thus reducing the attractive force exerted by annular pole pieces 12 on annular pole pieces 16, allowing the rotatable bearing element 14 to move away from the stationary bearing element 10. As the rotatable bearing element 14 moves away from the stationary bearing element 10, a point is reached where the force exerted by the second eddy current plate on the second slotted pole pair exceeds the force exerted by the eddy current plate 20 on the slotted pole pair 28, thus driving the shunt pair 26 away from annular pole pieces 12. This causes the force exerted by annular pole piece 12 on annular pole piece 16 to increase, thus driving the system to a new position of force equilibrium.

3B and 3C. Thermostat element 65 may be a sealed sylphon bellows with a vaporizable liquid or element 65 may be an assembly having a bimetallic element. Electrical signals, dependent upon the radial deviation in the position of the rotor from a predetermined position are applied to said winding such that the coils produce magnetic fields which are applied to the rotor and are of different magnitude or direction.

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  • Crónico: Estado con desarrollo gradual y a largo plazo
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The rotor includes narrow ring faces juxtaposed to said discs and a permanent magnetic polarization being provided between the narrow ring faces. In FIG. 5, within the vacuum enclosure 92, the remaining rotating elements of the module are a shaft 95 connected to a rotor 96 and a cylindrical Halbach array permanent magnet assembly 98 that produce the rotating field of the generator/motor assembly 99. The vacuum housing itself consists only of the chamber 92 and the re-entrant ceramic or glass-ceramic cylinder 100 through which the rotating field is inductively coupled to the windings that lie inside cylinder 100, thus outside of the evacuated region.