US1873354A - Core construction for magnetic circuits - Google Patents

Description

Aug. 23, 1932.

R. E. STEWART CORE CONSTRUCTION FOR MAGNETIC CIRCUITS Filed April 5, 1929 2 k2. Stew rt Willa/u Patented Aug. 23, 1932 UNITED STATES PATENT OFFICE RALPH E. STEWART, OF LOS ANGELES, CALIFORNIA, ASSIGNOR OF ONE-HALF TO CHARLES RUESS, OF LOS ANGELES, CALIFORNIA 003 CONSTRUCTION FOR MAGNETIC means Application filed April 3,

This invention relates to core constructions for magnetic circuits and to a construction which will prevent the crowding of magnetic flux in an electromagnetic construction wherein there is a primary winding and a secondary winding which are movable relatively to each other.

Anobject of the invention is to provide an improved laminated construction adaptedto be used in magnetic circuits which are energized by either an alternating current or a pulsating direct current. Heretofore it has bcen'customary to form laminated members in magnetic circuits which are energized by either alternating or pulsating direct currents by firmly and rigidly fastening the laminations together. If the laminated member or core is to come in contact with another member in the magnetic circuit a great deal of care involving time and expense is usually taken to mill off the abutting or engaging surfaces between the two members. An attempt is made to have the abutting surfaces as smooth and as exact as possible to allow the two members to fit closely together in an endeavor to prevent the creation of noise by the laminated member vibrating due to the changes in the magnetic flux.

It is an object of the present invention to provide an improved laminated construction which is so constructed that it will not produce the objectionable noise. It is usually found that regardless of the care taken in milling off the abutting surfaces between two members in a magnetic circuit that these two members vibrate under the influence of changes in the magnetic flux producing an objectionable noise and the improved con struction is highly advantageous in that the noise is practically completely eliminated.

It is another objectof the invention to provide an improved laminated construction to be used in magnetic circuits which will not only eliminate the objectionable noise but which will dispense with the expensive milling operations heretofore believed to be necessary in the construction of the laminated member.

The invention is highly useful when applied to a device such as a voltage regulator 1929. Serial No. 352,261.

in which there is a primary coil and a secondthe magnetic flux generated by the primary coil. This magnetic flux generated by the secondary coil in opposition to the primary coil or winding tends to crowd the flux of the primary winding away from the secondary coil. As a result of this it will be found that a curve representing the magnitudes of voltages or currents induced in the secondary winding is very peaked, instead of approaching a smooth curve similar to'a sine curve. This nature of the induced currents in the secondary winding is disadvantageous and it is another object of the invention to provide a construction on anelectromagnetic device which will prevent or resist the crowding of the flux generated by the primary winding so that the induced currents in the secondview which will be made manifest in the following detailed description and specifically pointed out in the appended claims reference is had to the accompanying drawing for an illustrative embodiment of the invention wherein:

Fig.1 is a perspective view of a voltage regulator to which the invention has been embodied.

Fig. 2 is a longitudinal vertical section taken through the same.

Fig. 3 is a vertical section taken substantially upon the line 33 upon Fig. 2.

Referring to the accompanying drawing for an illustrative embodiment of the invention it will be understood that the invention may be applied to any magnetic circuit under a variety of different circumstances. However, the invention haspractically no application to an electromagnetic circuit created by or energized by a direct current and therefore the invention is limited in its-application to a magnetic circuit which is energized by either an alternating current or a pulsating direct current. The invention 'is illustrated as havingbeen applied to a voltage regulator comprisin a lower rectangular frame part 10 whic has two upstanding posts 11 and 12 at its opposite ends connected by a guide 13. Transverse supporting members 14, 15 and 16 extend across the frame and serve to support the lower set of laminations forming the lower core 18. The lower set of laminations are loose, i. e. they are merely resting on the transverse supporting members 14, 15 and'16. They are not otherwise connected to each other and are merely held side by side by the sides of the lower frame part. Minute spaces are between the laminations, such spaces being represented by the relatively heavy lines on the drawing. By virtue of the fact that the laminations do not completely fill the frame between its side walls 19 and 20 each lamination is ca pable of moving slightly or vibrating independently of the others. Each lamination of the lower core has a recess '21 formed there .movable relatively to each other. The transverse members 24, 25 and 26 extend between the sides 27 and 28 of an upper movable frame,

the sides being connected by a back wall 29 which has an actuating screw 30 threadedly connected thereto. The actuating screw 30 is adapted to be rotated by a crank 31 which is journaled in the back wall of the lower frame 10. By rotation of the crank 31 the upper frame and the upper set of laminations, together with the upper coil 32 constituting the secondary winding can be adjusted with respectvto the lower set of laminations and the lower coil, the movement of the upper frame being guided by the guide 13. The voltage regulator is shown in Fig. 2 as being in approximately no-load position or in that position wherein little if any current is being induced in a secondary winding.

In the lower set of laminations 18 there are formed apertures 33 and in their top edges there are formed recesses 34. These apertures and recesses are adapted to receive copper bars 35 and 36 which extend transversely across the lower core. These copper bars extend through the sides 19 and 20 of the lower frame and are welded, brazed, or otherwise secured to copper plates 37 and 38 which are arranged on the outer sides of the side walls 19 and 20 within the sides of the primary coil 22. In this manner the bars 35 and 36 together with the blades 37 and 38 form a plurality of short circuited coils in the lower core, the axes ,of which are arranged at right angles to the axis of the primary winding 22 and parallel to the direction of movement of the secondary coil 32. o

The voltage regulator is adapted to be energized by either an alternating current or a pulsating direct current and a feature of the improved construction resides in the fact that the improved voltage regulator is practically noiseless. Each lamination being loose, can vibrate independently of the others due to the changes or variations in the magnetic flux. The theory of the improved construction is as follows:

When the laminations are all rigidly fastened together as in prior constructions and the abutting surfaces between the upper and lower cores are carefully milled oil it is practically impossible to have the abutting surfaces perfectly or exactly flat and smooth. Instead, there will always be one or more high pointson the abutting surfaces. By virtue of the fact that the laminations are all rigid with each other the variations or changes in the magnetic flux soon cause the laminated core to vibrate as an entire unit. The momentum developed by the large laminated core vibrating as a unit and pounding Y on-the high points on the abutting surfaces causes the upper laminated core to act like a hammer. This hammering on the high point or points produces the objectionable noise.

In the improved construction, however, each lamination can vibrate independently of all of the others due to the changes in the magnetic flux, but as each lamination is relatively small in weight the momentum of each lamination will likewise be small. In this manner, although the laminations will vibrate they will not necessarily vibrate in unison and each lamination does not have the momentum present to cause the ounding on the high point of the milled surface. Consequently, the noise generated by each inde pendent lamination vibrating against the surface is negligible and the sum or integral of the noises produced by all of the laminations is also practically negligible and at least is not objectionable. A feature of the improved construction resides in the fact that not only is the noise eliminated but that it is not necessary to go to the expense and trouble of milling off the abutting surfaces between the upper and lower cores. The edges of the laminations may be left in the same condition as that in which they were originally assembled and by virtue of the fact that the laminations are loose opposed laminations will accommodate themselves to each other and keep the magnetic leakage between the two laminated cores at a minimum.

The theory of the short circuited coils in the lower or primary winding is as follows: After the secondary winding 32 as shown in Fig. 2 is moved from left to ri ht some of the magnetic flux created by the primary winding enters the secondary winding inducing currents therein. These currents will develop a magnetic flux which may be considered as a back magnetic flux which works in opposition to the flux created by the pri-- mary winding 22. The effect of the back flux is to crowd the flux generated by the primary winding 22 toward the right of the primary coil so that it will passto the right of the right hand side of the secondary coil. Because of this crowding of the flux a curve representing the magnitudes of voltages or currents induced in the secondary coil will be quite peaked instead of conforming generally to a true sine curve. In the improved construction as the flux generated by the primary winding 22 is shifted or crowded over it will cut across the bars 35 and 36 inducing currents in these bars which in turn set up a counter magnetic flux in opposition to the shifting or crowding. This will counteract the effect of the back magnetic flux developed by the secondary winding 32 so that as the secondary winding is shifted over from no-load position to a loaded position the curve representative of the magnitudes of the voltages or currents induced therein will more nearly conform to a true sine curve having the attendant advantages.

From the above described construction it will be appreciated that a novel and advantageous laminated construction is provided which is adapted to be used in a magnetic circuit and which when placed in contact with another member in the magnetic circuit will accommodate itself thereto and produce the minimum amount of noise if any noise whatsoever. Furthermore, an improved form of voltage regulator is provided in which currents induced in the secondary winding will more nearlyconform to the characteristics of the currents impressed in the primary winding.-

Various changes may be made in the details of construction without departing from the spirit or scope of the invention as defined by the appended claims.

I claim:

1. In a magnetic circuit energized by either an alternating or a pulsating direct current,

two engaged opposed members adapted to be moved relatively to each other, at least one of said members being formed of laminations which are movable relatively to each other so that the laminations may vibrate independently, the edges of the laminations being in engagement with the other member.

2. In a magnetic circuit energized by either an alternating or a pulsating direct current, two engaged opposed members adapted to be moved relatively to each other, both of said members being formed of laminations which are movable relatively to each other so that the laminations may vibrate under the influence of changes in the magnetic flux independently of each other, the laminations of the members being so arranged as to be in edge to edge relation.

3. In a magnetic circuit adapted to be energized by either an alternating current or a pulsating direct current, two members adapted to engage each other, the engaging surfaces being substantially fi'at, one of the members being laminated with its flat surface formed by the flush edges of the laminations, said member being characterized by the fact that its laminations are loose so that they may vibrate independently of each other.

4. In a magnetic circuit adapted to be energized by either an alternating current or a pulsating direct current, two members adapted to engage each other the engaging surfaces being substantially flat, both of said members being laminated with their flat surfaces formed by the flush edges of the laminations, said members being characterized by the fact that their laminations are'loose so that they may vibrate independently of each other.

5. In a magnetic circuit adapted to be energized by either an alternating current or a pulsating direct current, two members adapted to engage each other the engaging surfaces being substantially flat, one of the members being laminated with the planes of its laminations arranged parallel to the path of the magnetic flux, said member having its flat surface formed by the flush edges of the laminations, and being characterized by the fact that its laminations are loose so that they may vibrate independently of each ot er.

6. In a magnetic circuit adapted to be energized by either an alternating current or a pulsating direct current, two members adapted to engage each other, said members presenting complementary engaging surfaces, one of themembers being laminated with its engaging surface formed by the edges of the laminations, said member being character ized by the fact that its laminations are loose so that they may be influenced by the magnetic flux independently of each other.

7. In a magnetic circuit adapted to be en ergized by either an alternating current or a pulsating direct current, two members adapted to engage each other, the engaging surfaces being substantially fiat, one of the members being laminated with the edges of the laminations cooperating to produce the surface, and means for holding the laminations in association in such a manner that the laminations are loose and may vibrate indeergized by either an alternating current or a pulsating direct current, two members adapted to engage each other, the engaging surfaces being substantially flat, one of the members being laminated with the edges of the laminations cooperating to produce the surface, and means for holding the laminations in association engaging the" outer sides of the outermost laminations in such a manner as to leave the laminations loose between the holding means and thus permit them to vibrate independently of each other.

9. In a magnetic circuit adapted to be energized by either an alternating current or a pulsating direct current, two members adapted to engage each other, the engaging surfaces being substantially flat, both of the members being laminated with the edges of the laminations cooperating to produce the surface, and means for holding the lamina-- tions ofeach member in association in such a manner that the laminations are loose and may vibrate independently of each other.

10. In a magnetic circuit adapted tobe energized by either an alternating current or a pulsating direct current, two members adapted to engage each other, the engaging surfaces being substantially fiat, both of the members being laminated with the edges of the laminations cooperating to produce the surface, and means for holding the laminations of each member in association engaging the outer sides of the outermost laminations in such a manner that the laminations will be loose and thus may vibrate independently of each other.

In testimony whereof I have signed my name to this specification.

RALPH E. STEWART.

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