Square wave pulse generator

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Feb. 9, 1965 A.‘ J. LAVIN ETAL 3,169,203 SQUARE WAVE PULSE GENERATOR Filed March 28, 1961 4 Sheets-Sheet 1 FIG. 9 WWI/‘M5 ;: 'i ANDREW J. LAVIN 2 WENDELL J.…
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Feb. 9, 1965 A.‘ J. LAVIN ETAL 3,169,203 SQUARE WAVE PULSE GENERATOR Filed March 28, 1961 4 Sheets-Sheet 1 FIG. 9 WWI/‘M5 ;: 'i ANDREW J. LAVIN 2 WENDELL J. WHEELER Feb. 9, 1965 A. J. LAVIN ETAL 3,169,203 SQUARE WAVE PULSE GENERATOR Filed March 28, 1961 4 Sheets-Sheet 2 FIG. 3 Feb. 9, 1965 A. J. LAVIN ETAL 3,169,203 SQUARE WAVE PULSE GENERATOR Filed March 28. 1961 4 Sheets-Sheet 3 Q .2“on Feb. 9, 1965 A.‘ J. LAVIN ETAL 3,169,203 ' SQUARE WAVE PULSE GENERATOR Filed March 28. 1961 4 Sheets-Sheet 4 United States ‘Patent 6 lcé 3,169,203 Patented Feb. 9, 1965 ' if _ 2 ?eld. It ‘is also to be noted that there are no non-uniform amazes I magnetic ?elds in~the air gap as found in generator con SQUARE WAVE PULSE GENERATOR ~ Andrew J. Lavin, Union, and Wendeil .l'. Wheeier, End structions having'open winding slots. These non-uni! well, N.Y., assignors to international Business Machines form magnetic ‘fields of the latter construction are due Corporation, New York, N.Y., a corporation of New to the‘cornering effects or magnetic ?eld concentration at York corners. Filed Mar. 28, 19511, Ser. No. 9%,885 Accordingly, a prime object of the invention is to pro 9 (Ilaims. . (Cl. 310-456) vide an improved alternating current generator capable of generating an alternating current voltage having a square This invention relates to dynamo-‘electric machines and, or rectangular waveform. ' particularly, to alternating current generators having a A very important object of the invention is to provide ' permanent magnet excitation system and capable of gen an improved alternating current generator wherein the erating voltages having a square or rectangular waveform. amount of ?ux, whether it be increasing or decreasing, Attempts made heretofore to achieve a voltage having linking any one winding is controlled. - a' square or rectangular Waveform have not been particu 15 Another very important object of the invention is to larly successful because of the approaches taken. in provide an improved alternating current generator which order to achieve a voltage waveform, ap'proachinga rec maintains ‘substantially a uniform and constant reluctance tangular or squared condition, the rise and decay time in all magnetic circuit paths. ’ should be small compared to the period and the ratio of Still another very importantobject of the invention is rise and decay time to the period should be substantially to provide an alternating current generator which gener constant for all frequencies. _ 1 ates a voltage waveform derived from a ?ux linkage curve The voltage Waveform is discontinuous in character. having substantially a constant’slope and an abrupt change Since the voltage waveform is the derivative of the ?ux in slope from one direction to an opposite direction. linkage curve, the flux linkage curve is therefore neces The foregoing and other objects, features and advan sarily a sawtooth form with the slope changing abruptly tages'of the invention will be apparent from the following from one direction to an opposite direction. The points more particular description of preferred embodiments of where the flux linkage curve changes direction are the thepinvention, as illustrated in the accompanying drawings. 1 points of discontinuity of the voltage waveform. These In the drawings: points are related to each other in a linear manner. FIG. ‘1 isa front elevational view in section showing ' In order to satisfy the basic condition imposed by the the rotor and stator ofsthe alternating current generator; flux linkage curve; i.e., that the slope-thereof be constant ' PEG. 2 is a side elevational view of the rotor; ‘ ‘ and that the slope change abruptly from ‘one direction to FIG. 3 is a sectional view of an alternating current an opposite direction, it has been ascertained that certain generator having'a series‘ of axially spaced associated geometrical relationships must exist. The ratio of polar rotors and stators to provide a generator'capable ‘of gen- / to interpolar spaces of the rotor is one to one and the 35 crating a series, of alternating current voltages ‘having ’ number of polar and interpolar spaces is equal to the square or rectangularv Waveforms of different phase rela number of stator teethof the stator, the stator teeth being tionships; ' ‘ symmetrically arranged. Hence, the ratio of rotor poles ‘ FIG. 4 is a diagram showing a series of curves to stator teeth in each‘output phase is one to one, there and C, curve A being illustrative ofthe magnetic ?eld’, as being one or two output phases depending upon the coil 40 it , actually exists, curve B being illustrative of the flux winding arrangement upon'the stator‘ teeth. The width of linkages developed as the. rotor rotates relative toa single the rotor poles and stator teeth should be the same and ‘ winding of the stator, and‘ curve‘C‘ being illustrative of,‘ equal to one-half the pitch. The coils in which the volt the voltage developed in the single winding; . I . 4 ‘age is generated are individually wound upon each stator FIGS. 5a, ‘5b, 5c, 5d and 5e show the development of. tooth in a manner that the voltage is due entirely to the the ?ux linkage curve; . time rate of change of ?ux linkage. The amount of‘ FIGS. 6a, 6b and. 6c are a series of developed views to ,1 ?ux linking any one coil winding is controlled so that the illustrate that only a controlled amount of the primary. flux linkage curve has substantially a constant‘slope with magnetic polar ?eld is permitted to link any .one of the coil the slope changing direction abruptly. This‘ is accom windings as the rotor moves relative thereto, hence de- . plished by providing a magnetic circuit path for the flux scribing a ?ux linkage curve having a constant slope with’ which is not to link the coil windings vwith an equivalent the slope changing directionabruptly; reluctance to, that of the magneticIcircuit path for the ?ux FIG. 7 is a front elevational view schematically illus- i which is tolink any one coil Winding. Having provided trating an alternate embodiment of the‘. invention; such a magnetic path for the nonlinking ?ux, the portion FIG. 8 is a perspective view schematically illustrating of the primary polar ?eld linking the coil winding is di» the embodiment ofthe invention shown in FIG. 7; and, rectly related in time to the motion of ?eld moving rela-' FIG. 91(Sheet 1) is a fragmentary view of the stator . tive to‘the coil Winding. The amount of flux which-is to with every tooth containing a coil Winding to. provide link any one coil winding varies according to the position two output phases. of the induced magnetic ?elds produced by the rotor poles U Referring to the drawings and particularly to ‘1, with respectlto said any one coil winding. ~ . 00 the invention is illustrated by way of example as an. controlgover the amount of ?ux‘ linking anyone coil alternatlngcurrent generator 10 capable of generating ‘an ~ winding is achieved, by providing ‘an inner stator ring hav alternating current voltage‘, having a square or rectangu ing‘ a nondnterrupted or continuous surface. This ar lar waveform.‘ The alternating current’ generator 10 com- . rangement substantially maintains a uniform reluctance I apnses a stator. and rotor housing‘and support 11, a' in all magnetic circuits. The stator is a continuous ring 05 “laminated stator ring 15 and a fabricated rotor 40. provided with arcuately spaced closed Winding slots en- ‘ The stator ring '15, FIGS.‘ 1 and 3, is formed ‘from a tered into laminations forming the stator. The width of plurality of laminations lj6'of electrical iron, each ,lami the section of the stator at the, bottom of the winding nation 16 being provided with aseries of arcuately spaced ' slots adjacent the rotor surface is maintained at a small closed Winding slots 17, FIG.“ 1,” which are ‘punched sectional thickness. Hence, the material at this point into the laminations 16. The closed winding slots 17, saturates at a low level'of magnetic induction and pre have a teardrop con?guration and are positioned so as vents any noticeable magnetic shorting of ‘the primary to present a small sectional thickness near the inner‘ ‘ 3,169,203 S A peripheral surface of the stator ring 15. Hence, the width of the rotor poles and virtual stator teeth is sub stator ring 15 is constructed in a manner to furnish sub stantially equal and equal to one-half the pitch and the stantially a uniform reluctance to the magnetic ?elds coils are individually wound on the virtual stator teeth. through all magnetic paths. This arrangement provides Furthermore, the amount of ?ux linking any one winding magnetic paths of substantially equivalent reluctance for coil 18 is controlled by providing a magnetic path of linking and nonlinking ?uxes. Hence, the linking flux equivalent reluctance for the nonlinking flux. is directly related in time to the motion of the '?eld. The stator 15'is mounted within the housing 11 as Further, by maintaining the width of the section of the shown in FIG. 3. Essentially, the housing 11 is cylin stator ring 15 at the bottom of the winding slot adjacent drical in shape and the inner periphery thereof is recessed the rotor surface at a small sectional thickness, the 10 at 21 to receive the stator rings 15. The rim 22 of the material at this point then saturates at a small level of housing ll is slotted so that a pinching or gripping force magnetic induction and prevents any noticeable mag may be exerted upon the stator rings 15 through the netic shorting of the primary ?eld. Since the inner facility of bolts 23 extending through bores 24 and peripheral surface of the stator ring 15 is continuous, a secured by means of nuts 25 screwed onto threaded por separated tooth or salient tooth stator does not exist. 15 tions 26 of the bolts 23, as shown in FIGS. 1 and 2. Accordingly, the stator will be considered to have virtual The shaft 41 bearing the pair of axial spaced rotors 15 teeth. During any one output phase, certain virtual is journalled within the housing ll by conventional bear teeth will provide the magnetic circuit for the linking ing assemblies 5%» and 51. The rotor 4a is adapted to ' ?ux while other virtual teeth provide the magnetic cir be rotated at ‘approximately 12,000 r.p.m. cuit for nonlinking ?ux. Of course, because the inner 20 Curve A of FIG. 4 represents the magnetic ?eld as it peripheral surface of the stator ring is continuous, flux actually exists relative to the stator. Brie?y, the ?eld straying in the stator does not occur. For a single phase form ‘was obtained by a magnetic ?eld measuring instru output, the closed winding slots 17 are threaded by coils ~ment, not shown, employing a Hall probe evaporated on of wire 18 as shown in FIG. 1. The number of turns ' the inside of a ring which simulates the pulse generator of Wire in a coil 18 of course depends upon the wire stator ring. The rotor journalled concentrically with the size and the desired output from, the generator 10. A measuring instrument is rotated relative to the probe. double phase output with the outputs 90° out of phase Hence, the permanent magnet rotor ?eld is determined may be had by winding coils of wire 18 upon each virtual in a magnetic circuit similar to that of the generator. tooth as- in FIG. 9. It is to beunderstood that, with The ?eld form has also been obtained by mathematical the coil windings 18 on each virtual tooth, one tooth analysis employing conformal mapping techniques. will provide a magnetic path for the linking ?ux while Curve B of FIG. 4 illustrates the ?ux linkages developed adjacent teeth provide magnetic paths for nonlinking ?ux. as the rotor rotates relative to a single winding of the In this example, the stator ring 15 is actually con stator. The ?ux linkage curve is plotted against the dis structed by applying a dry ?lm adhesive to the lamina placement of the rotor poles as they move past a virtual tions 16 and then curing the composite structure under 'stator tooth, as shown in FIGS. 5a, 5b, 5c, 5d and 5e. pressure for a predetermined time at an elevated temg In FIG. 5a,’ the north pole is out of the area directly‘ perature. The amount of pressure applied is equal to that ' under the virtual stator tooth. Under these conditions, required to maintain speci?ed stator ring thickness in a the flux linkage curve B, FIG. 4, is at point 1, the ?ux ?xture.’ Excellent results were achieved by curing the linkages being zero. As the rotor rotates, the north adhesive for approximately ten minutes at a temperature 40 pole becomes directly aligned with the virtual stator tooth, of 320° F. as shown in FIG. 5b, and the ?ux linkage curve B, FIG. 4, ‘The rotor 40 is fabricated according to techniques is at point 2, the ?ux linkages being at a maximum for alreadywell known in the art. In this example, the the particular polarity. Upon further rotation of the rotor 40 is mounted upon a central shaft 41, FIGS. 1, 2 rotor, the north pole moves out from directly under the and 3. The rotor 4t), FIG. 1, is a composite member virtual stator tooth, as in FIG. 50, and the ?ux linkage consisting of a central hexagonally shaped core 42 of curve B is at point 3, again the flux linkages being zero. electrical iron which embraces the shaft 41. There is a As the rotor continues to rotate, a south pole becomes T-shaped permanent magnet 43 mounted on each, face directly aligned with the virtual stator tooth, as in FIG. of. the central hexagonal core 42 in a manner that the 5d, and the flux linkage curve B, FIG. 4, is at point 4, t leg of the T faces outwardly. To assure a substantially 50 with the ?ux linkages being at a maximum for the uniform magnetic ?eld across the pole face, soft iron particular polarity. Further rotation of the rotor moves shoes 44 are attached to the outer surfaces of the per the south pole out from under the virtual stator tooth, manent magnets. The soft iron shoes 44 are formed as in FIG. 5e, and the flux linkage curve B is at point 5, from laminations 45, as seen in FIG. 2. The rotor the flux linkages being zero; assembly 40. is ?anked on each side by a pair of stain The voltage generated in the coils l8 threading the less steel plates 46 and 47 which are held in spatial winding slots 17 is due to the time rate of change of ‘relationship by means of rivets 48. All of the com flux linkages, which is the derivative of the ?ux linkage ponents in the assembly are then bonded together with curve, FIG. 4, curve B. The voltage curve C, FIG. 4, a cold flow aluminum ?lled epoxy resin represented by is positive for that portion of the flux linkage curve reference character 49. The permanent magnets 43 are polarized so that alternate poles have the same polarity which is increasing and is negative for that portion where and adjacent poles are of opposite polarity. In this the ?ux linkage curve a decreasing slope. example, all poles are magnetically balancedwith a FIGS. 6a, 6b and 6c illustrate the flux which links maximum variation from pole to pole of approximately and which does not link any one coil winding as the 2-percent. . rotor is moved relative thereto. It is seen that in FIG. It is seen that the rotor 41) has the same number of 6a all the ?ux from, the rotor pole is linking the coil poles as the ‘stator ring 15 has winding coils 13 for any winding. The flux linkage curve under this condition a one output phase and that the angular spacing of the two is at a maximum for the particular polarity, as at point 2, is substantially thev same. The width of. the pole shoes PEG. 4, curve B. As the rotor pole moves to the po 44. is substantially equal to the width of the virtual 70 sition shown in FIG. 6b, approximately one-half of the teeth of the stator ring'15. Accordingly, the basic con ?ux of the total ?ux from’ the rotor pole links the coil ditionsimposed by-the ?ux linkage curve'are satis?ed; winding, while the other half of the flux is returned by that is, the ratio of the number of rotor poles onv the a magnetic path having a reluctance equivalent to the rotor 49 to the number of virtual stator teeth of the vmagnetic: path for the linking flux, as at point 6, FIG. 4, stator ring 15‘ in each output phase is one to one and‘the curve B. In FIG. 6c, the rotor pole has been moved to‘ greases a position where none of the flux links the coil winding,’ 6 as at point 3, FIG. 4, curve B. ' magnetic circuit for the flux linking said coils has substah tially the same reluctance of the magnetic circuit for the In generator constructions known heretofore, some non-linking ?ux so. that a voltage'wave form with discon of the ?ux which was not to link the coil winding did tinuities is generated in‘each coil due to the time rate of link it because the magnetic path for the linking ?ux change of flux linkages as said rotor and statorrelatively was of less reluctance than theone for the nonlinking rotate uniformly. ' ?ux. Consequently, more ?ux would link the coil wind 2. In the combination of a stator and a concentrically ings to result in a flux linkage curve having a noncon mounted rotatable rotor having permanent magnet excita stant slope and not changing direction abruptly. tion for a square wave generator, the improvement com~ FIGS. 7 and 8 show an alternate embodiment for the 10 prising: a continuous inner surface for said stator to pro invention. This embodiment, at the present time, is less vide a uniform reluctance to magnetic ?elds, said stator preferred because it is more diilicult to construct. How having a plurality of arcuately spaced closed winding slots ever, with the advent of new materials, it and other equiv with the winding slots terminating at said continuous inner alent embodiments may become more practical. The alternate embodiment essentially consists of a surface to provide a sectional thickness which becomes magnetically saturated'to prevent shorting of the magnetic stator 60 and rotor 80, each being in the general shape 1.5 ?elds and still provide magnetic circuits for linking and of a disk. The stator 60 is preferably fabricated from non-linking ?ux with substantially the same reluctance; a a series of concentric laminations of electrical iron to plurality of coils, each coil threading said winding slots form a disk having a central opening or core 61. Wind in pairs; and a plurality of polarized arcuately spaced ing slots 62 extend from the outer periphery to the inner radially extending poles for said rotor whereby, upon periphery of the disk'and have their axes located along rotation of said rotor, a voltage wave form having dis radial lines. One end of the winding slots terminate continuities due to the time rate of change of magnetic along one face 63 of the disk to present a small sectional flux linkages is generated within each coil winding. thickness near the face 63 and to provide virtual stator » 3. A square wave generator comprising: a stator ring teeth 64. The face 63 furnishes substantially a uniform 25 having a continuous inner peripheral surface to provide a reluctance to the magnetic ?elds in all paths. The closed uniform constant reluctance, said stator ring having a winding slots are threaded by coils of wire 65, as in plurality of arcuately spaced closed winding slots through FIGS. 7 and 8. Of course, every virtual tooth may be which coils of wire are threaded, said slots terminating wound to provide two outputs displaced 90° from each at said continuous inner peripheral surface to provide a other. ‘ 30 sectional thickness which becomes magnetically saturated The rotor 80, made of magnetic material, is attached to prevent shorting of the magnetic ?elds and still provide to a shaft 81 of nonmagnetic material. The shaft 81 magnetic circuits for linking and non-linking ?ux with is adapted to be driven by any suitable means. Poles substantially the same reluctance; a plurality of coils, 82 of the rotor 80,,best seen in FIG. 8, are magnetized each coil threading saidwinding slots in pairs; and
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