US3889220A - Stacked magnetic arrangement - Google Patents

Stacked magnetic arrangement Download PDF

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Publication number
US3889220A
US3889220A US372707A US37270773A US3889220A US 3889220 A US3889220 A US 3889220A US 372707 A US372707 A US 372707A US 37270773 A US37270773 A US 37270773A US 3889220 A US3889220 A US 3889220A
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parts
permanent magnet
stack
magnet
magnet arrangement
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US372707A
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Heinrich Spodig
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F7/00—Magnets
    • H01F7/02—Permanent magnets [PM]
    • H01F7/0205—Magnetic circuits with PM in general
    • H01F7/021—Construction of PM

Definitions

  • Tha ratio L /D L is the length of the permanent magnet (in centimeters).
  • D is the diameter (in centimeters) of a rodshaped permanent magnet of circular cross section.
  • the D is the diameter of a circle having an area equal to the cross-sectional area of the permanent magnet of non-circular cross section.
  • HM (expressed in oersteds) is the magnetic field intensity within the permanent magnet, as indicated by the working point on the second quadrant portion of the hysteresis curve of the magnet.
  • the product L 'H is equal to the magmetomotive force ofthe magnet, sometimes referred to as the magnetic potential drop across the magnet poles.
  • L is the length of the air gap (in centimeters) measured along the direction of flux travel
  • H (in oersteds) is the intensity of the magnetic field in the air gap.
  • L 'H is equal to the so-called magnetic potential drop across the air gap. It is useful to remember that if the air gap is of very short length, the intensity of the air-gap magnetic field l-I will have approximately the same numerical value as the flux density B of the magnetic field in the air gap, provided that the field intensity H, is expressed in oersteds and the flux density is expressed in gausses.
  • the product F 'B This product is equal to the total flux (1) flowing through the permanent magnet, and in the gaussian system of units is expressed in maxwells.
  • B is the flux density of such total flux. also referred to as the induction at the magnet poles, and F is the cross-sectional area (in cm of the path travelled by the magnetic flux d).
  • the flux density or induction can be conversely defined as B (in gausses) d) (in maxwells) divided by F," CHILE).
  • the continuing development in the field of ferromagnetic steels and ferrimagnetic materials was mainly characterized by the continual increase in the coercive forces of the magnetic materials produced.
  • the coercive force H rose gradually from 30 to 60 to to 200 to 300 to 500 to 600 to 1,000 to 1,500 to 2,000 and up to 4,000 oersteds.
  • the high coercive force of these newly developed materials which is a desirable property, is accompanied by an undesirable decrease in the residual induction B,..
  • the materials developed exhibited higher and higher magnetomotive forces L -H and had higher and higher specific magnetization resistances H along the length L of permanent magnets formed from the newly developed materials.
  • the fiux density or induction value at the poles became smaller and smaller.
  • a disadvantage of the newly developed magnetic materials is that they are more expensive than the magnetic materials they are supplanting, such as the older aluminum, nickel, and cobalt steel alloys, etc.
  • a magnet arrangement comprising, in combinations, a stack of members including at least two permanent magnet members and at least one intermediate member of soft magnetic material having a permeability higher than that of the permanent magnet members and sandwiched between the permanent magnet members.
  • the magnet arrangement has the' form of a stack of permanent magnet members of high coercive force, made from relatively expensive magnetic material, alternating with members of higher permeability, such as iron, and having a much lower cost.
  • FIG. 1 shows the second quadrant of the hysteresis curves for several different magnetic materials
  • FIGS. 2a and 2b are views of a plate of magnetic material, in elevation and in side view;
  • FIGS. 3-8 illustrate six different stack-like magnet arrangements
  • FIG. 9 is a graph of induction and magnetic field intensity versus magnet length for each of the different permanent magnet arrangements shown in FIGS. 3-8.
  • the magnetic length L of the permanent magnet plates such as the one shown in FIGS. 2a and 2b, was 2.5 cm. Accordingly, for the permanent magnetplates of ferrite material, the ratio L /D 0.44. This value lies within the optimal range mentioned above of LM/DM S 0.5.
  • magnet arrangements were formed by simply stacking together different numbers of ferrite magnet plates such as shown in FIG. 2. The field intensity and induction of one such plate was measured. Then the field intensity and induction of a stack of two such plates was measured, then three such plates, and so on, up to a stack of sixteen ferrite permanent magnet plates such as shown in FIG. 3. In each stack, all the magnet members had the same north-south orientations. The stack of sixteen plates shown in FIG. 3 had a length of 40 cm.
  • the flux density or induction B (in gausses) was measured by measuring the voltage in a coil drawn out of the neutral zone of the respective formed stack; this kind of technique is very common and is known to persons familiar with the principles of voltage induction.
  • the measurement of the magnetic field intensity H (measured in oersteds) was accomplished using a Hall probe at the pole surfaces of the respective magnet stacks.
  • the intermediate plates of soft magnetic material had a thickness of 1 cm.
  • the intermediate plates of soft magnetic material had respective thicknesses of 2 cm, 2.5 cm, 3 cm and 4 cm.
  • FIGS. 3 8 Each of the six stacks shown in FIGS. 3 8 was built up, plate by plate, and after the addition of each plate to each stack, measurements were taken of the field intensities and flux densities of the different stacks. These results are shown in FIG. 9, which is a graph of flux density B (in gausses) and also of field intensity H (in oersteds) versus stack length L The curves are derived from discrete measurements but the points of the graphs have been connected by smooth lines to facilitate visualization. In each of FIGS. 3-8, above the respective magnet stack, there is depicted the key for correlating the different stacks with the different curves appearing in FIG. 9.
  • the upper set of curves represents the variation of flux density B with varying stack length for all six stacks depicted.
  • the lower set of curves represents the variation of magnetic field intensity H with varying stack length for all six stacks depicted.
  • the lower set of curves representing field intensity H it will be noted that for the stacks shown in FIGS. 4-8, there are two curves for each stack such as curves 4a and 4b, 5a and 5b, etc.
  • the curves 4a-8u depict the field intensities of the respective stacks when the upper end plate is a ferrite permanent magnet plate; the curves 4b8b depict the field intensities of the respective stacks when the upper end plate is a plate of soft magnetic material.
  • interpolations have been made to yield continuous curves, instead of a point graph. to facilitate visualization of the results achieved.
  • the graphs 4a-8a and 4b8b do indicate, however. a significant difference in properties depending on whether or not the upper end plate (in the case of the measurements here taken) was'of ferrite permanent magnet material or of iron.
  • the upper end plate was of ferrite permanent magnet material (the curves marked 3a-8a) the field intensity was markedly higher than when the upper end plate was of soft iron (the curves marked 4b-8h).
  • the discrepancy in H values increases significantly with increases in the thicknesses of the intermediate soft-iron plates. In the stack of FIG. 4, for example, where the intermediate soft-iron plates are only 1 cm thick, the difference between curves 4a and 4b, representing the difference resulting from the kind of material selected for the end plate, is not very great.
  • the intermediate plates of soft magnetic material there is no comparable restriction as to the thickness of the intermediate plates of soft magnetic material; these plates may be quite thick, to save on the expen sive permanent magnet material of the other plates, without too great a reduction in magnetic field intensity H.
  • the intermediate plates to a great extent serve only to increase the magnetizability of the stack-type arrangement according to the invention, compared to the much more difficult magnetization of the permanent magnet material employed.
  • the magnetic length of the intermediate pole-shoe plates of soft magnetic material such as iron is kept less than or equal to the length of the permanent magnet plates, which in the illustrated embodiment means less than or equal to 2.5 cm.
  • a plurality of stacks of members like those shown, of different lengths, and of different configurations, can be combined to form larger magnet arrangements, with of course the north-south orientations of the various combined stacks being kept the same.
  • the optimal (but not mandatory) relationship L /D 0.5 should still be observed, however, with respect to the total magnetic length and effective magnetic diameter of the resulting composite structure.
  • the magnetic stacks according to the invention, or composite structures formed from a plurality of such stacks can be used in combination with iron flux-return members to build magnetic circuitry of the type used in many different conventional applications.
  • inventive concept when implemented results in a reduction in the amount of expensive permanent magnetic material, for instance ferrite magnetic material, needed to construct a magnet having a certain field intensity and flux density.
  • inventive concept if furthermore advantageous insofar as the actual process of initially magnetizing the materials in question is concerned. For example, if a stack of unmagnetized hard ferrite members alternating with soft iron members is placed in a strong magnetizing field, the magnetomotive force of the magnetizing field can be substantially less than when a similar stack composed entirely of hard ferrite material is to be magnetized.
  • the normal or virgin magnetization curve of the composite according to the invention if initially unmagnetized, will have a shape representing a composite of the low-permeability characteristics of the hard ferrites and the high-permeability characteristics of the soft magnetic material.
  • the resulting composite characteristic results in easier magnetization, that is, the use of smaller magnetomotive forces to effeet the initial magnetization, compared to what is required when similarly configurated magnets of hard ferrite material are being initially magnetized. Accordingly, lower magnetizing currents can be used to effect the initial magnetization. As will be understood by those skilled in the art, this advantageous increase in the magnetizability of the magnet arrangement Will result, in effect, even if the hard ferrite members are magnetized individually prior to formation of the stack structure according to the invention.
  • a magnet arrangement comprising, in combination, a stack of parts including at least two permanent magnet parts having respective first end faces of the same magnetic polarity and respective second end faces of the same magnetic polarity, said first end faces having a magnetic polarity opposite to the magnetic polarity of said second end faces, and an intermediate part made of a magnetic material having a magnetic permeability higher than the permeability of said permanent magnet parts and sandwiched between said permanent magnet parts and having a first end face juxtaposed with the first end face of one of said permanent magnet parts and an opposite second end face juxtaposed with the second end face of the other of said permanent magnet parts.
  • said stack is an elongated stack comprisedof permanent magnet parts alternating with intermediate parts having a permeability higher than the permeability of the permanent magnet parts, and wherein one end of said stack is a north-pole end and the other end of said stack is a south-pole end, and wherein each of said permanent magnet parts has a north-pole end facing towards said north-pole end of said stack and facing away from said south-pole end of said stack, and wherein each of said permanent magnet parts has a south-pole end facing towards said south-pole end of said stack and facing away from said north-pole end of said stack.
  • a magnet arrangement as defined in claim 2 wherein said permanent magnet parts are non-metallic and wherein said intermediate members are metallic 12.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Manufacturing Cores, Coils, And Magnets (AREA)
  • Permanent Field Magnets Of Synchronous Machinery (AREA)
  • Coils Or Transformers For Communication (AREA)
  • Iron Core Of Rotating Electric Machines (AREA)
US372707A 1972-07-03 1973-06-26 Stacked magnetic arrangement Expired - Lifetime US3889220A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE2232613A DE2232613A1 (de) 1972-07-03 1972-07-03 Verfahren zur verbesserung des magnetisierungsverhaltens, insbes. aller schwer und sehr schwer magnetisierbaren permanentmagnetischen ferro-, ferri-magnetmaterialien zur erzielung hoher flussdichten b tief m (g) und feldstaerken h tief m (oe) bei gleichzeitiger sehr erheblicher einsparung an nutzbarem, teurem magnetmaterial

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US3889220A true US3889220A (en) 1975-06-10

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US372707A Expired - Lifetime US3889220A (en) 1972-07-03 1973-06-26 Stacked magnetic arrangement

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US (1) US3889220A (en, 2012)
BE (1) BE800919A (en, 2012)
CH (1) CH566633A5 (en, 2012)
DE (1) DE2232613A1 (en, 2012)
ES (1) ES416435A1 (en, 2012)
FR (1) FR2191227B1 (en, 2012)
GB (1) GB1432969A (en, 2012)
IT (1) IT988282B (en, 2012)
NL (1) NL7309177A (en, 2012)
SE (1) SE398020B (en, 2012)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4114532A (en) * 1976-10-12 1978-09-19 Dataproducts Corporation Impact printer magnet assembly
US4609109A (en) * 1982-07-06 1986-09-02 Cryogenic Consultants Limited Superconducting magnetic separators
US4675609A (en) * 1985-09-18 1987-06-23 Fonar Corporation Nuclear magnetic resonance apparatus including permanent magnet configuration
US4707663A (en) * 1985-08-15 1987-11-17 Fonar Corporation Nuclear magnetic resonance apparatus using low energy magnetic elements
DE29515302U1 (de) * 1995-09-25 1995-11-30 Rheinmagnet Horst Baermann GmbH, 53819 Neunkirchen-Seelscheid Magnetanordnung
US20130082545A1 (en) * 2010-06-08 2013-04-04 Kengo Goto Linear Motor
WO2017155788A1 (en) * 2016-03-08 2017-09-14 Weatherford Technology Holdings, Llc Position sensing for wellsite pumping unit
US11098708B2 (en) 2015-08-05 2021-08-24 Weatherford Technology Holdings, Llc Hydraulic pumping system with piston displacement sensing and control

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19628722A1 (de) * 1996-07-17 1998-01-22 Esselte Meto Int Gmbh Vorrichtung zum Deaktivieren eines Sicherungselementes für die elektronische Artikelsicherung

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2947921A (en) * 1957-02-25 1960-08-02 Brown & Sharpe Mfg Fine grid permanent magnetic chuck
US3206655A (en) * 1954-04-22 1965-09-14 Philips Corp Magnet system comprising two structurally identical parts
US3535200A (en) * 1967-09-18 1970-10-20 Gen Motors Corp Multilayered mechanically oriented ferrite

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1098804A (fr) * 1953-03-26 1955-08-22 Int Standard Electric Corp Structure d'amplificateurs à ondes progressives
US3153177A (en) * 1962-09-11 1964-10-13 Ketcham And Mcdougall Inc Magnetic holder for paper clips

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3206655A (en) * 1954-04-22 1965-09-14 Philips Corp Magnet system comprising two structurally identical parts
US2947921A (en) * 1957-02-25 1960-08-02 Brown & Sharpe Mfg Fine grid permanent magnetic chuck
US3535200A (en) * 1967-09-18 1970-10-20 Gen Motors Corp Multilayered mechanically oriented ferrite

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4114532A (en) * 1976-10-12 1978-09-19 Dataproducts Corporation Impact printer magnet assembly
US4609109A (en) * 1982-07-06 1986-09-02 Cryogenic Consultants Limited Superconducting magnetic separators
US4707663A (en) * 1985-08-15 1987-11-17 Fonar Corporation Nuclear magnetic resonance apparatus using low energy magnetic elements
US4675609A (en) * 1985-09-18 1987-06-23 Fonar Corporation Nuclear magnetic resonance apparatus including permanent magnet configuration
DE29515302U1 (de) * 1995-09-25 1995-11-30 Rheinmagnet Horst Baermann GmbH, 53819 Neunkirchen-Seelscheid Magnetanordnung
US20130082545A1 (en) * 2010-06-08 2013-04-04 Kengo Goto Linear Motor
CN102948053B (zh) * 2010-06-08 2015-11-25 株式会社日立制作所 线性电机
US11098708B2 (en) 2015-08-05 2021-08-24 Weatherford Technology Holdings, Llc Hydraulic pumping system with piston displacement sensing and control
WO2017155788A1 (en) * 2016-03-08 2017-09-14 Weatherford Technology Holdings, Llc Position sensing for wellsite pumping unit
US10344573B2 (en) 2016-03-08 2019-07-09 Weatherford Technology Holdings, Llc Position sensing for wellsite pumping unit

Also Published As

Publication number Publication date
DE2232613A1 (de) 1974-01-24
BE800919A (fr) 1973-10-01
SE398020B (sv) 1977-11-28
NL7309177A (en, 2012) 1974-01-07
FR2191227A1 (en, 2012) 1974-02-01
CH566633A5 (en, 2012) 1975-09-15
IT988282B (it) 1975-04-10
FR2191227B1 (en, 2012) 1976-09-17
ES416435A1 (es) 1976-03-01
GB1432969A (en, 2012) 1976-04-22

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