Magnetic damping system having low induction magnet
AssigneeWestinghouse Electric Corp.
InventorsJohn A. MacFadden, Joseph M. Keever
Life of this patent
Estimating the term…
Abstract
A magnetic damping system for induction devices having electroconductive disk armatures includes a low induction, high coercive force magnet that is vertically elongated and has a horizontal direction of magnetization parallel to the disk. Flux concentrating pole pieces adjoin the magnet pole faces for vertically directing two closely spaced braking magnetic fields from a pair of pole tips and into the disk. A temperature compensating arrangement covers the sides of the permanent magnet between the edges of the pole pieces to efficiently compensate for higher reversible temperature coefficients of magnet remanence.
Claims20
A magnetic damping system for an induction device magnetically driving an electroconductive disk, said magnetic damping system comprising:
- an elongated upright permanent magnet means having a direction of magnetization parallel to said disk and along a short length thereof extending between opposite magnet pole faces each having an upright height substantially greater than said length;
- flux concentrating pole piece means formed of a soft magnetic material adjoining said opposite pole faces and having edge portions extending along the height thereof and terminating at pole tip portions passing a pair of closely spaced and flux density concentrated braking magnetic fields into said disk;
- and
- temperature compensating magnetic means having a negative temperature coefficient of permeability and magnetically coupling coaligned pairs of said edge portions of said pole piece means to form compensating magnetic shunt paths between said opposite pole faces.
A magnetic damping system for an induction meter device having an electroconductive disk armature rotatable at a rate proportional to a quantity to be measured, said magnetic damping system comprising:
- first and second permanent magnet assemblies mounted on opposite sides of said electroconductive disk;
- first and second substantially identical permanent magnets included in said first and second assemblies, respectively, each of said first and second permanent magnets having a vertically elongated rectangular block configuration with a direction of magnetization parallel to a short length thereof and to said electroconductive disk so that opposite pole faces thereof have a substantially longer height extending substantially vertically of an outer edge of said electroconductive disk;
- first and second pairs of flat flux concentrating pole piece members made of a soft magnetic material included in said first and second assemblies, respectively, each of said pairs of pole piece members covering one of said opposite pole faces of an associated permanent magnet in an adjoining and closely magnetically coupled relationship, and each of said pole piece members terminating at a pole tip portion focusing the associated pole face magnetic field into a predetermined disk receiving air gap space and aligned with a pole tip portion of a oppositely magnetically poled pole piece member of the other permanent magnet assembly, such that a pair of oppositely unidirectional high flux density braking magnetic fields are each directed into said electroconductive disk in a predetermined pattern substantially elongated along a disk radius;
- and
- first and second temperature compensating magnetic means included in said first and second permanent magnet assemblies, respectively, each of said first and second temperature compensating magnetic means including a magnetic material having a negative temperature coefficient of permeability covering in an adjacent relationship the sides of an associated permanent magnet and extending between the opposite pole faces thereof, and further covering in an adjoining and closely magnetically coupled relationship the aligned sides of an associated pair of pole piece members for variably shunting the pole face magnetic fields in an inverse relationship to changes in temperature.
Dependencies are inferred from the claim text.