US2959736A - Moving-coil electrical instruments - Google Patents

Moving-coil electrical instruments Download PDF

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US2959736A
US2959736A US2959736DA US2959736A US 2959736 A US2959736 A US 2959736A US 2959736D A US2959736D A US 2959736DA US 2959736 A US2959736 A US 2959736A
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coil
magnetic
moving
magnet
slot
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R5/00—Instruments for converting a single current or a single voltage into a mechanical displacement
    • G01R5/02—Moving-coil instruments
    • G01R5/08—Moving-coil instruments specially adapted for wide angle deflection; with eccentrically-pivoted moving coil

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  • This invention relates to moving-coil electrical instruments and has particular relation to moving-coil electrical measuring instruments wherein a coil side is disposed for rotation in an air gap of a magnetic structure.
  • a radially magnetized permanent magnet has been positioned intermediate a pair of inner and outer magnetic pole pieces.
  • the inner pole piece is spaced from the inner periphery of the magnet to define an air gap for an outer coil side of a moving coil.
  • the coil has an opposed inner coil side which is positioned in an opening of the inner pole piece.
  • the inner pole piece is provided with a slot extending from the outer periphery to the central opening of the inner pole piece. This slot is proportioned to permit passage of the inner coil side of the moving coil into the opening of the inner pole piece for permitting assembly of the coil with respect to the inner pole piece.
  • a mag netic plug ordinarily formed of a high permeability material is inserted into the slot subsequent to installation of the moving coil to close the slot for providing an efficient magnetic circuit. It has been observed, however, that with previous arrangements of the type described, the slot has not been sufficiently closed by the magnetic plug to obtain a magnetic circuit of the desired efficiency.
  • a moving co'il instrument is provided with improved means for permitting the installation and removal of the moving coil.
  • an inner magnetic pole piece is surrounded by a substantially C-shaped permanent magnet with the inner membar and magnet in spaced relation to define an air gap.
  • the magnet is surrounded by and is in engagement with an outer magnetic member which is integrally connected to the inner magnetic member.
  • the inner member includes a slot which extends from the outer periphery thereof to a central opening of the inner member to permit the installation and removal of a moving coil with respect to the inner member.
  • the invention provides that the side walls of the slot have ice 'fit condition to thereby effectively close the slot for providing an efficient magnetic circuit.
  • the plug is preferably formed of a high permeability magnetic material such as soft iron.
  • Figure 1 is a view in top plan of an electrical instrument embodying the teachings of the invention
  • Fig. 2 is a view taken along the line II-II of Fig. l;
  • Fig. 3 is an exploded view in perspective of a magnetic member and associated magnetic plug of the instrument of Figs. 1 and 2.
  • the instrument 1 includes a source of magnetomotive force comprising a permanent magnet 3 constructed of any suitable permanent magnet material.
  • the magnet 3 is preferably of substantially C-shaped configuration having an opening 5 bounded by the inner periphery 7 of the magnet.
  • the magnet 3 further includes an outer periphery 9 and an open side 11. netized such that magnetic flux traversed the magnet in directions extending radially of the axis of the magnet.
  • a suitable magnetic structure In order to provide a magnetic path for magnetic flux emanating from the magnet 3, a suitable magnetic structure is provided.
  • This structure includes an inner magnetic member or pole piece 13 constructed of a suitable magnetic material such as soft iron.
  • the member 13 is of substantially ring-shaped configuration having a central opening 15 and an outer periphery 17. As shown in Fig. 1, the member 13 is positioned within the opening 5 of the magnet 3 to be surrounded by the magnet 3.
  • the outer periphery 17 of the member 13 is spaced A from the inner periphery 7 of the magnet 3 to define an air gap 19 which is arcuate about the axis of the magnet 3.
  • the magnetic structure includes further an outer ringshaped member or pole piece 21 which may also be formed of soft iron.
  • the member 21 has a central opening 23 bounded by the inner periphery 25 of the member 21.
  • the magnet 3 is positioned within the opening 23 of the member 21 with the outer periphery 9 of the magnet in engagement with the inner periphery 25 of the member 21.
  • the members 13 and 21 are preferably magnetically connected to provide a low reluctance path for flux of the magnet 3.
  • the members 13 and 21 are conveniently integrally connected to provide a magnetic circuit of one-piece construction.
  • a connecting neck portion 29 extends from the inner periphery 25 of the member 21 to the outer periph-.
  • the magnet 3 is mag-.
  • the one-piece magnetic circuit comprising the parts 13, 21 and 29 is preferably formed of a plurality of identical magnetic laminations 30. Each of these laminations has the configuration shown in Fig. 1.
  • the instrument 1 further includes a moving-coil 31 of substantially rectangular configuration as shown in Fig. 2.
  • the coil 31 includes an inner coil side 33 and an outer coil side 35 which define a pair of spaced parallel axes. It is noted that the inner coil side 33 is positioned to extend through the opening of the member 13 with the outer coil side 35 positioned in the air gap 19.
  • the coil 31 is secured to a shaft 37.
  • the shaft 37 extends through the opening 15 of the member 13 concentrically of the axis of the opening 15 and is supported at its ends by a pair of spaced bearing members 39 and 41.
  • a suitable pointer 43 is secured to the shaft 37 for movement with the coil 31.
  • the pointer 43 moves with respect to a suitably calibrated scale 45 to indicate the magnitude of the energizing quantity.
  • an instrument is provided having a substantially circular scale with a range of movement of the pointer 43 of approximately 270 C.
  • a suitable control spring 48 is provided to oppose movement of the pointer 43 as is understood in the art.
  • a suitable slot 47 is provided in the member 13 which extends from the outer periphery 17 to the opening 15.
  • the slot may be located at any angular position about the axis of the shaft 37.
  • the slot is formed in the member 13 at the open side 11 of the magnet 3 adjacent the connecting neck 29. The slot is proportioned to permit passage of the inner coil side 33 of the coil through the slot relative to the opening 15 of the member 13.
  • the slot 47 includes a pair of side walls 49 and 51 which are cut away or recessed to provide recesses 53 and 55 of the side walls of arcuate configuration. This construction is best shown in Fig. 3.
  • the recesses 53 and 55 are preferably configured so as to define a passage 57 of cylindrical configuration having an axis extending transverse to the direction of extension of the slot 47.
  • the passage 57 and slot 47 may conveniently b formed by a single stamping operation wherein material of each lamination is removed to provide the properly configured slot and passage.
  • the invention provides a magnetic plug 59 proportioned to substantially entirely fill the passage 57.
  • the plug 59 is preferably formed of a high permeability magnetic material such as soft iron,
  • the present invention provides that the plug 59 is in the form of a cylinder having a radius substantially equal to the radius of the cylindrical passage 57.
  • This arrangement provides a press fit condition of the plug 59 to thereby permit the installation and removal of the plug 59 relative to the passage 57.
  • Such arrangement further provides a very efiicient magnetic circuit inasmuch as the plug 59 substantially entirely fills the passage 57 with extremely small clearance between the plug and the walls of the recesses 53 and 55.
  • the axial dimension of the plug 59 is selected to be substantially equal to the thickness dimension of the pole piece 13.
  • a source of magnetomotive force a paramagnetic body providing a magnetic path for magnetic flux produced by said source, said body comprising an outerbody portion having an aperture therein and having a substantially ring-shaped portion located in said aperture, said ring-shaped portion having a first opening defining an inner periphery, said ringshaped portion having an outer periphery providing a side wall of an air gap arcuate about an axis extending parallel to said first opening and located in said aperture, a coil having an inner coil side positioned in said first opening and an outer coil side positioned in said air gap, means mounting said coil for rotation about said axis to carry said outer coil side through said air gap relative to said source and ring-shaped portion, said ring-shaped portion having a passageway completely cutting thereacross through which a portion of said coil may be passed to permit said coil and said ring-shaped portion to be assembled, the portions of said ring-shaped portion adjacent said passageway forming spaced walls, each said wall comprising spaced surface portions and

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  • General Physics & Mathematics (AREA)
  • Electromagnets (AREA)

Description

Filed June 10, 1957 INVENTOR Lawrence J. Luncls WITNESSES BY W 9 4;
ATTORN EY United Sttes Patent MOVING-COIL ELECTRICAL INSTRUMENTS Lawrence J. Lunas, Cedar Grove, N.J., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed June 10, 1957, Ser. No. 664,759
1 Claim. (Cl. 324-150) This invention relates to moving-coil electrical instruments and has particular relation to moving-coil electrical measuring instruments wherein a coil side is disposed for rotation in an air gap of a magnetic structure.
In many instruments it has been found desirable to provide an air gap defined by a magnetic pole piece and a source of magnetomotive force which surrounds the pole piece to establish a magnetic field in the air gap. A moving coil has a coil side disposed in the air gap and is mounted for rotation relative to the magnetic pole piece. Such instruments have been found useful as relays and in other fields and the invention is applicable thereto. However, the invention is particularly suitable for an electrical measuring instrument of the foregoing type and will be discussed with reference to such a measuring instrument.
'In instruments heretofore constructed, a radially magnetized permanent magnet has been positioned intermediate a pair of inner and outer magnetic pole pieces. The inner pole piece is spaced from the inner periphery of the magnet to define an air gap for an outer coil side of a moving coil. The coil has an opposed inner coil side which is positioned in an opening of the inner pole piece. .In such instruments, the problem arises as to the manner of installing and removing the moving coil with respect to the inner pole piece.
'In instruments of this type previously constructed, the inner pole piece is provided with a slot extending from the outer periphery to the central opening of the inner pole piece. This slot is proportioned to permit passage of the inner coil side of the moving coil into the opening of the inner pole piece for permitting assembly of the coil with respect to the inner pole piece. A mag netic plug ordinarily formed of a high permeability material is inserted into the slot subsequent to installation of the moving coil to close the slot for providing an efficient magnetic circuit. It has been observed, however, that with previous arrangements of the type described, the slot has not been sufficiently closed by the magnetic plug to obtain a magnetic circuit of the desired efficiency.
In accordance with the present invention, a moving co'il instrument is provided with improved means for permitting the installation and removal of the moving coil. In a preferred embodiment of the invention, an inner magnetic pole piece is surrounded by a substantially C-shaped permanent magnet with the inner membar and magnet in spaced relation to define an air gap. The magnet is surrounded by and is in engagement with an outer magnetic member which is integrally connected to the inner magnetic member. The inner member includes a slot which extends from the outer periphery thereof to a central opening of the inner member to permit the installation and removal of a moving coil with respect to the inner member.
In order to provide an efficient magnetic circuit, the invention provides that the side walls of the slot have ice 'fit condition to thereby effectively close the slot for providing an efficient magnetic circuit. The plug is preferably formed of a high permeability magnetic material such as soft iron.
It is therefore an object of the invention to provide a moving-coil electrical instrument of improved construction.
It is another object of the invention to provide a moving-coil instrument having a magnetic circuit with improved means permitting the installation and removal of the coil with respect to the magnetic circuit.
It is a further object of the invention to provide a moving-coil instrument having a magnetic circuit including a magnetic member having a slot through which the moving coil may be assembled to the member with improved means permitting effective closure of the slot subsequent to assembly of the coil.
Other objects of the invention will become apparent from the following description taken in conjunction with the accompanying drawings, in which:
Figure 1 is a view in top plan of an electrical instrument embodying the teachings of the invention;
Fig. 2 is a view taken along the line II-II of Fig. l; and
Fig. 3 is an exploded view in perspective of a magnetic member and associated magnetic plug of the instrument of Figs. 1 and 2.
Referring to the drawings, there is illustrated in Fig. 1 an electrical measuring instrument of the moving-coil type represented generally by the numeral 1 embodying the teachings of the present invention. the instrument 1 includes a source of magnetomotive force comprising a permanent magnet 3 constructed of any suitable permanent magnet material. The magnet 3 is preferably of substantially C-shaped configuration having an opening 5 bounded by the inner periphery 7 of the magnet. The magnet 3 further includes an outer periphery 9 and an open side 11. netized such that magnetic flux traversed the magnet in directions extending radially of the axis of the magnet.
In order to provide a magnetic path for magnetic flux emanating from the magnet 3, a suitable magnetic structure is provided. This structure includes an inner magnetic member or pole piece 13 constructed of a suitable magnetic material such as soft iron. The member 13 is of substantially ring-shaped configuration having a central opening 15 and an outer periphery 17. As shown in Fig. 1, the member 13 is positioned within the opening 5 of the magnet 3 to be surrounded by the magnet 3. The outer periphery 17 of the member 13 is spaced A from the inner periphery 7 of the magnet 3 to define an air gap 19 which is arcuate about the axis of the magnet 3.
The magnetic structure includes further an outer ringshaped member or pole piece 21 which may also be formed of soft iron. The member 21 has a central opening 23 bounded by the inner periphery 25 of the member 21. The magnet 3 is positioned within the opening 23 of the member 21 with the outer periphery 9 of the magnet in engagement with the inner periphery 25 of the member 21.
The members 13 and 21 are preferably magnetically connected to provide a low reluctance path for flux of the magnet 3. For this purpose, the members 13 and 21 are conveniently integrally connected to provide a magnetic circuit of one-piece construction. As shown in Fig. 1, a connecting neck portion 29 extends from the inner periphery 25 of the member 21 to the outer periph-.
As there shown,
The magnet 3 is mag-.
cry 17 of the member 13 to connect the members 13 and 21,
The one-piece magnetic circuit comprising the parts 13, 21 and 29 is preferably formed of a plurality of identical magnetic laminations 30. Each of these laminations has the configuration shown in Fig. 1.
The instrument 1 further includes a moving-coil 31 of substantially rectangular configuration as shown in Fig. 2. The coil 31 includes an inner coil side 33 and an outer coil side 35 which define a pair of spaced parallel axes. It is noted that the inner coil side 33 is positioned to extend through the opening of the member 13 with the outer coil side 35 positioned in the air gap 19.
'In order to mount the coil 31 for rotation to carry the coil side 35 through the air gap 19, the coil 31 is secured to a shaft 37. As best shown in Fig, 2, the shaft 37 extends through the opening 15 of the member 13 concentrically of the axis of the opening 15 and is supported at its ends by a pair of spaced bearing members 39 and 41. With this arrangement, when the coil 31 is energized the coil side 35 will move through the air gap 19 about the axis of the shaft 37 relative to the magnet 3 and relative to the inner and outer members 13 and 21.
In order to permit an indication of the magnitude of an electrical quantity energizing th coil 31, a suitable pointer 43 is secured to the shaft 37 for movement with the coil 31. The pointer 43 moves with respect to a suitably calibrated scale 45 to indicate the magnitude of the energizing quantity. With the arrangement as described, an instrument is provided having a substantially circular scale with a range of movement of the pointer 43 of approximately 270 C. A suitable control spring 48 is provided to oppose movement of the pointer 43 as is understood in the art.
In order to permit installation and removal of the coil 31 with respect to the inner member 13, a suitable slot 47 is provided in the member 13 which extends from the outer periphery 17 to the opening 15. The slot may be located at any angular position about the axis of the shaft 37. Preferably, however, the slot is formed in the member 13 at the open side 11 of the magnet 3 adjacent the connecting neck 29. The slot is proportioned to permit passage of the inner coil side 33 of the coil through the slot relative to the opening 15 of the member 13.
In accordance with the invention, the slot 47 includes a pair of side walls 49 and 51 which are cut away or recessed to provide recesses 53 and 55 of the side walls of arcuate configuration. This construction is best shown in Fig. 3. The recesses 53 and 55 are preferably configured so as to define a passage 57 of cylindrical configuration having an axis extending transverse to the direction of extension of the slot 47.
The passage 57 and slot 47 may conveniently b formed by a single stamping operation wherein material of each lamination is removed to provide the properly configured slot and passage.
In order to close the magnetic circuit provided by the member 13 subsequent to installation of the coil 31 through the slot 47, the invention provides a magnetic plug 59 proportioned to substantially entirely fill the passage 57. The plug 59 is preferably formed of a high permeability magnetic material such as soft iron,
The present invention provides that the plug 59 is in the form of a cylinder having a radius substantially equal to the radius of the cylindrical passage 57. This arrangement provides a press fit condition of the plug 59 to thereby permit the installation and removal of the plug 59 relative to the passage 57. Such arrangement further provides a very efiicient magnetic circuit inasmuch as the plug 59 substantially entirely fills the passage 57 with extremely small clearance between the plug and the walls of the recesses 53 and 55. The axial dimension of the plug 59 is selected to be substantially equal to the thickness dimension of the pole piece 13. By providing cylindrical configurations of the passag 57 and plug 59 extremely accurate dimensions may be obtained for the plug and passage.
Although the invention has been described with reference to certain specific embodiments thereof, numerous modifications are possible and it is desired to cover all modifications falling within the spirit and scope of the invention.
I claim as my invention:
In an electrical instrument, a source of magnetomotive force, a paramagnetic body providing a magnetic path for magnetic flux produced by said source, said body comprising an outerbody portion having an aperture therein and having a substantially ring-shaped portion located in said aperture, said ring-shaped portion having a first opening defining an inner periphery, said ringshaped portion having an outer periphery providing a side wall of an air gap arcuate about an axis extending parallel to said first opening and located in said aperture, a coil having an inner coil side positioned in said first opening and an outer coil side positioned in said air gap, means mounting said coil for rotation about said axis to carry said outer coil side through said air gap relative to said source and ring-shaped portion, said ring-shaped portion having a passageway completely cutting thereacross through which a portion of said coil may be passed to permit said coil and said ring-shaped portion to be assembled, the portions of said ring-shaped portion adjacent said passageway forming spaced walls, each said wall comprising spaced surface portions and a circularly cylindrical intermediate surface portion connecting said spaced surface portions, said cylindrical surface portions having a common axis of curvature and comprising a substantial portion of said walls, and a fully circularly cylindrical paramagnetic closure member of a diameter to lie wholly within said passageway and to substantially fill the cross section of said passageway, the wall portions of said closure member adjacent said cylindrical surface portions seating snugly thereagainst.
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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3139581A (en) * 1964-06-30 Long scale moving coil electrical measuring instrumet
US3144603A (en) * 1964-08-11 Long scale moving
US3333193A (en) * 1967-07-25 Eccentrically pivoted coil type meter including flux path adjustments and severable coil supporting frame
US3434054A (en) * 1963-09-27 1969-03-18 Weston Instruments Inc Moving coil electrical instrument having a magnetic shunt movable transversely in a flux leakage path

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US996377A (en) * 1906-12-12 1911-06-27 Gen Electric Electric measuring instrument.
US1022517A (en) * 1908-07-30 1912-04-09 Gen Electric Electrical measuring instrument.
US1917289A (en) * 1931-12-17 1933-07-11 Chicago Electric Mfg Co Self-starting induction motor
US2167649A (en) * 1935-11-07 1939-08-01 Duncan Electric Mfg Co Electric meter
US2221643A (en) * 1940-11-12 Electrical measuring instrument
US2465053A (en) * 1949-03-22 Eccentric moving coil electrical
US2515014A (en) * 1950-07-11 Electrical measuring instrument

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2221643A (en) * 1940-11-12 Electrical measuring instrument
US2465053A (en) * 1949-03-22 Eccentric moving coil electrical
US2515014A (en) * 1950-07-11 Electrical measuring instrument
US996377A (en) * 1906-12-12 1911-06-27 Gen Electric Electric measuring instrument.
US1022517A (en) * 1908-07-30 1912-04-09 Gen Electric Electrical measuring instrument.
US1917289A (en) * 1931-12-17 1933-07-11 Chicago Electric Mfg Co Self-starting induction motor
US2167649A (en) * 1935-11-07 1939-08-01 Duncan Electric Mfg Co Electric meter

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3139581A (en) * 1964-06-30 Long scale moving coil electrical measuring instrumet
US3144603A (en) * 1964-08-11 Long scale moving
US3333193A (en) * 1967-07-25 Eccentrically pivoted coil type meter including flux path adjustments and severable coil supporting frame
US3434054A (en) * 1963-09-27 1969-03-18 Weston Instruments Inc Moving coil electrical instrument having a magnetic shunt movable transversely in a flux leakage path

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