US2077186A - Current responsive device - Google Patents

Description

A ril 13, 1937. T. A. RICH 2,077,186

CURRENT RESPONSIVE DEVICE Filed Oct. 22. 1956 2 Sheets-Sheet 1 7 34 flnventor'z Theodore A.Rich,

by M

Hi5 Attorney.

April 13, 1937. T. A. RICH CURRENT RESPONSIVE DEVICE Filed-Oct. 22, 1936 2 Sheets-Sheet 2 Inventor: "Theodore A. Rich,

His Attorney.

Patented Apr. 13, 1937 UNITED STATES CURRENT RESPONSIVE DEVICE Theodore A. Rich,

Schenectady, N. Y., assignor to General Elect c Company, a corporation of New York Application October 22, 1936, Serial No. 107,002

6 Claims.

In carrying out my invention in its preferred form, I provide a field structure with a pair of annular pole pieces and a shaft extending through said pole pieces. A flat spiral of current-conducting material attached at the inner end to the shaft and at the outer end to the stationary portion of the apparatus is mountedpn the shaft between the pole pieces and is provided with current connections. The arrangement is such that radial force produced on the current-conducting spiral by the reaction between the current and the magnetic flux tends to wind or unwind the spiral, thus producing rotation of the shaft.

My invention may be understood more readily from the following detailed description when considered in connection with the accompanying drawings and the features of my invention which a're believed to be novel and patentable will be pointed out in the claims appended hereto. In the drawings, Fig. 1 represents schematically in elevation one embodiment of my invention employing a single current-conducting spiral; Fig. 2

.is a plan view of the arrangement disclosed in Fig. 1; Fig. 3 is a diagram illustrating the principle of operation of the invention; Fig. 4 is a plan view of a modified form of my invention in which one of the pole pieces is split to provide two air gaps and accommodate two currentconducting spirals; Fig. 5 is an elevation of the arrangement of Fig. 4; Fig. 6 is a fragmentary sectional view of the arrangement of Fig. 5 cut by a plane 6-6 passing throughthe axis of the armature of the instrument; Fig. 7 shows a modification of the arrangement of Figs. 4, 5, 5 and 6 illustrating the application of my invention to wattmeters or to alternating-current circuits; Fig. 8 is an elevation of a modified arrangement in which no magnet is required; and Fig. 9

is a view of a section cut through the apparatus of Fig. 8 by a plane 9-9. Like reference characters are utilized throughout the drawings to designate like parts.

Referring more in detail to Figs. 1 and 2, the stationary portion of the apparatus includes the field structure consisting of a permanent magvnet H with annular pole pieces l2 and 13, a scale I4, and bearings, not shown. The annular pole pieces l2 and 13 are substantially similar, substantially coaxial, and axially spaced to provide an air gap l5 between them.

Th'e movable portion of the apparatus comprises a rotatable shaft IS, the current-conducting'spiral I! within the air gap l5, and a pointer l8 carried by the shaft IE to cooperate with the scale 14. The shaft l6 passes through the openings in the annular pole pieces I 2 and I3 substantially coaxial therewith and the currentconducting spiral I! is attached at the inner end to the shaft l6 and at the outer end to an insulated pin l9 attached to one of the pole pieces I3 or attached at some other suitable position to the stationary portion of the apparatus. The

pin l9 forms one of the current-conducting terminals of the apparatus and the other terminal 20 may be connected to the shaft I6 in any suitable manner, as e. g., by means of a substantially torsionless current-conducting spiral in the manner usual to current-responsive instruments of the dArsonval type.

If desired, suitable damping means may be provided, such asa damping vane 2| of currentconducting material mounted on an arm 22 carried by the shaft IS. The damping vane 2| is in close proximity to the inner cylindrical surface 23 (Fig. 2) of the pole piece I 2. The eddy currents induced in the damping vane 2| provide an effective means for bringing the movable element to a stop and preventing vibration thereof.

' It is evident that the magnet ll produces magnetic flux passing axially across the air gap I 5 between the pole pieces I! and I3. The current flowing through the spiral ll passes perpendicularly to the lines of flux and, consequently, as shown in Fig. 3, the reaction between the flux and the current produces forces acting on the spiral ligament ll perpendicular to the successive portions of the ligament l I and also perpendicular to the shaft l6. Accordingly, each part of the ligament I1 is subjected to a force acting in the plane of the ligament I! through the center of the spiral formed by the ligament ll. Depending upon the direction of current and the polarity of the pole pieces, the forces will be either outward or inward. In case the current direction is such that the forces are radially inward, as illustrated by the arrows in Fig. 3, the spiral ligament II will tend to wind up, thus rotating the shaft l8. In the case of a spiral wound as shown, the shaft will be rotated in the clockwise direction. On the other hand, in the case of reversal in the direction 01' current or reversal in polarization oi. the magnet II, the spiral l1 will tend to unwind and rotate the shaft It in the opposite direction. For reasons later to be'explained, the former arrangement may give greater sensitivity.

It is apparent that the angle of deflection oi the shaft I 8 is not limited to a fraction or 360 degrees but that a very long scale instrument may be produced. In fact, it. a suitable overhanging bearing support is provided which will not be struck by the pointer 18, the shaft i6 may be caused to rotate through a plurality of revolutions. Ii desired, a separate biasing spring orother suitable biasing means may be provided for maintaining the pointer l8 in a predetermined zero position. However, it is apparent that such a biasing means is unnecessary in my construction for the reason that the current-conducting spiral il itself serves as a biasing spring and, in

the case of center-zero instruments, serves to bias the pointer to a position in the center of the scale. i

In connection with Figs. 1 and 2, it was mentioned that the current connection between the terminal 28 and the shaft l8 might take the form of a current-conducting spiral or hairspring. For the sake of obtaining increased torque and for effective utilization of material, such a second current-conducting spiral may be arranged in a second air gap, as shown in Figs. 4, 5 and 6. In the arrangement of Figs. 4, 5, and 6, the pole pieces are interleaved. One 01 the pole pieces is forked or split into two parts, 24 and 25, each of which is annular and is spaced axially from an annular pole piece 26 in order to form a pair of air gaps 21 and 28. A pair of current-conducting spirals 28 and 30 are provided in the air gaps 21 and 28, respectively, and each of the current-conducting spirals 29 and 30 has its inner end attached to the shaft [6 or to a current conductor carried thereby and the outer ends of the current-conducting spirals 28 and 30 are electrically connected to binding posts 3i and 32, respectively, serving as the terminals of the instrument. The binding posts 3| and 32 are supported by the field structure but insulated therefrom. The torque produced by the two spirals is in the same direction on IS.

Preferably, the current-conducting spiral ligaments H or 29 and 30 are composed of a material which combines the properties of high current conductivity and high flexibility. I have 3 found certain copper alloys to be suitable for this purpose. For example, an alloy of 2.6% cobalt, 97% copper, and 0.4% beryllium may be employed. The ligaments may be in the form of thin strips in order to be sufliciently rigid to maintain the proper position axially in the air gap and still offer very little resistance to bending. The exact thickness will, of course, be determined by the current to be carried and the desired lull-scale reading of the instrument, which in turn determines the amount oi. control torque desired for calibration purposes.

\ In the arrangement of Figs. 4, 5,'and 6, the shaft I6 is mounted between cupped jewels carried in'the ends of jewel screws 33 and 34, re-

spectively. The jewel screws 33 and 34 are inounted in 'suitablalijrackets 38 and 36, respec ively.

In the embodiments of my invention shown in with the armature so as to form an instrument having a modified relationship between current and deflection. Such an instrument may also be employed for alternating currents, in which case, the field structure is preferably partially laminated.

In Fig. '7, I have shown one manner of utilizing an electromagnet in connection with my invention for providing a magnetic field. The arrangement of Fig. 7 is connected for use as a wattmeter. It will be seen that the pole pieces [2 andl3 are attached to a yoke 31 upon which is wound a field coil 38. The coil 38 is connected in series with the electrical circuit 39 and the armature of the instrument is' connected across the circuit 39 through a resistor 40. The field coil 38 accordingly serves as a current winding and the spiral ligaments .29 and 38 serve as a potential winding of an instrument in which a torque is produced varying with the product of the instantaneous values of current and voltage. For use in alternating-current circuits, the yoke 31 is preferably laminated and the pole pieces l2 and i3 may also be partially laminated.

It will be understood that my invention is not limited to the use of any particular form of damping mechanism. For example, in the arrangement of Figs. 5 and 6, the damping element takes the form of a disk I carried by the shaft IS in one of the air gaps and, as the shaft l6 rotates, it causes the disk H to cut the magnetic center scale is desired, the arrangement will or-- dinarily be such that the flux produced by the permanent magnet II or the solenoid winding 38 is relatively large compared with the flux produced by the current flowing in the currentconducting spiral I'I. When such a directional effect is not desired, this consideration need not be had but the arrangement will preferably be such that the current-conducting spiral ll tends to wind up rather than unwind is the current therein increases. It is evident that, in adjacent turns of the spiral ll, current is flowing in the same direction and the reaction between such currents is such as to tend to draw the successive turns together. The resultant effect of the reaction between the current in successive turns of the spiral thus tends to close or wind the spiral quite independently of any magnetic flux which may be produced by a field structure. Consequently, the torque produced by reaction between the currents in successive turns of the spiral may be caused to aid the torque produced by the reaction between the current in the spiral and the fiux produced by the field structure, and the sensitivity may be increased if the arrangement is such that the reaction between the current in the spiral and the fiux produced by the field structure tends to wind up the spiral Il.

When it is desired to produce zero-center instruments having different sensitivities in one direction or the other, the characteristic just described may be made use of and the design may be such as to bring about a relationship between field fiux and current which causes the reaction between the current in adjacent turns to suppress the scale for one direction of deflection and to expand the scale of the instrument for the other direction of deflection.

A modified arrangement is disclosed in Figs.

8 and 9 in which the reaction between the currents flowing in successive turns of the spiral I1 is relied on for producing the turning moment of the armature of the instrument. Preferably, but not necessarily, a pair of currentconducting spirals 29 and 3ll is employed and is mounted in the manner already described on a shaft l6 and terminals 3| and 32 and occupies air gaps 26 and 21. The field structure, however, is preferably-composed entirely of soft iron or some other suitable highly permeable magnetic material and consists of a block of soft iron 43 with the slots 26 and 21 cut therein to form air gaps. Suitable openings are drilled therein to receive the shaft I6. The soft iron field structure 43 serves to increase the sensitivity of the instrument by reducing the magnetic reluctance of the space surrounding the current-conducting spirals 29 and 30, respectively. It will be apparent that the instrument illustrated in Figs. 8 and 9 is a universal instrument and may be employed for measuring either alternating or direct currents. The pointer I8 will tend to move in the direction corresponding to winding up the spirals 29 and 30, irrespective of the direction of current flow.

I have herein shown and particularly de-' scribed certain embodiments of my invention and certain methods of operation embraced therein for the purpose of explaining its principle and showing its application, but it will be obvious to those skilled in the art that many modifications and variations are possible and I- aim, therefore,

to cover all such modifications and variations as fall within the scope of my invention which is defined in the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A current-responsive device comprising in combination, a field structure having a pair of pole pieces, a relatively rotatable member, and a pair of current-conducting spirals, one of said pole pieces having substantially parallel pole faces on either side thereof and the other of said pole pieces being forked, the inner surfaces .of the forked portion being substantially parallel to form pole faces, said first pole piece and said forked pole piece being interleaved with their pole faces substantially parallel and spaced to form a pair of air gaps, said current-conducting spirals each being mounted in one of said air gaps substantially parallel to said pole faces, the outer ends of said current-conducting spiral being mechanically connected to said field structure and electrically insulated therefrom and the inner ends of said current-conducting spirals being mechanically and electrically connected to ing in combination a field structure having a pair of annular pole pieces substantially coaxial and axially spaced to form an air gap therebetween, a fiat current-conducting spiral within said air gap substantially perpendicular to the axis of said annular pole pieces, a rotatable shaft substantially coaxial with said pole pieces, and a damping loop carried by said shaft and linking one of said annular pole pieces, said loop forming a closed electrical circuit, the inner end of said current-conducting spiral being attached to said shaft and the outer end thereof being fixed in a stationary position.

3. A current-responsive instrument comprising in combination, a field structure having a pair of pole pieces with substantially parallel confronting pole faces spaced to form an air gap therebetween, a fiat current-conducting spiral mounted in said air gap substantially parallel to said pole pieces, a rotatable member mounted with its axis of rotation substantially perpendicular to said pole faces, and a. damping member of current-conducting material mounted on said rotatable member and intersecting the path of lines of fiux between said pole faces, the innerend of said current-conducting spiral being attached to said rotatable member and the outer end being fixed in a stationary position.

4. A current-responsive wattmeter for an electrical circuit comprising in combination, a stationary member including a magnetic field structure of magnetizable material having a pair of pole pieces with substantially parallel confronting pole faces spaced to form an air gap therebetween and a current-conducting winding in inductive relation with said magnetizable field structure, a fiat current-conducting spiral mounted in said air gap substantially parallel to said pole faces, and a rotatable member with an axis of rotation substantially perpendicular to said pole faces, the inner end of said current-conducting spiral being attached to one of said members and the outer end being attached to the other of said relatively rotatable members, said field winding and said current-conducting spiral each being connected to the electrical circuit in which watts are to be measured, one being connected in responsive relation to the current in said circuit to serve as a current winding and the other being connected in responsive relation to the voltage across said circuit to serve as a potential winding.

5. A zero-center current-responsive device with unequal scale distributions on either side of the zero points comprising in combination, a pair of relatively rotatable members and a current-conducting spiral, said spiral being connected at the inner end to one of said members and at the outer end to the other of said members, one of said members including a magnet having a pair of pole pieces with confronting substantially parallel pole faces spaced to form an air gap therebetween, the axis of relative rotation of said members being substantially perpendicular to said pole faces, said current-conducting spiral being mounted in saidair gap, the strength of the magnet being such that appreciable winding torque is produced by the reaction between the current in the turns of the spiral relative to unwinding or winding torque which is produced by the reaction between the current in the spiral and the fiux produced by the magnet.

6. A current-responsive device comprising in substantially parallel conironting surfaces spaced combination, a pair of relatively rotatable memto form an air gap therebetween, the axis of relabers and a current-conducting spiral, said spiral tive rotation of said members being mbstantially being connected at the inner end to one or said perpendicular to said confronting surfaces and 5 members and at the outer end to the other of said said current-conducting spiral occupying said 5' members, one of said members comprising magair gap.

netizable material formed into a structure having THEODORE A. RICH.

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