US 1762775 A
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g June 10, 1930. A. G. GANZl INDUCTANCE DEVICE Filed sept. 19. 1928v Z3 ZZ AGGANz. BY l Arron/ver Patented June 1o, 1930 UNITED STATES PATENT OFFICE ALBERT G. GANZ, OF UNION CITY, NEW JERSEY, ABSIGNOR TO BELL. TELEPHONE LAB- ORATOBIES, INCORPORATED, I' N EW YORK, N- Y., A CORPORATION 0F NEW YORK INDUCTANCE DEVICE Application filed September 19, 1928. Serial No. 306,877.
This invention relates to inductance appay ratus for connecting electrical circuits and particularly to transformers.
An object of this invention is to provide a 5 transformer which will transfer waves'` between two circuits with low energy loss and.
variation may be of considerable importance.
These changes may cause a mismatching of the im pedances of the circuits at various frequencies which may cause reflection losses und distortion.
In the case of the joiningof two carrier circuits of different characteristics, it was found that as the frequency increased the effective series resistance of the windings of the connecting transformer also increased, disturbing the matched impedance condition of the joined circuits, and causing excessive reflection losses and poor transmission at the higher frequencies. One reason for this increase in effectiveseries resistance of the windings of the transformer with fre uency was found to be that the unbalanced ux of the load currents cutting the turns of the windings set up eddy currents in the wires of the transformer windings. l
To illustrate briefly, the portion of the load flux, cutting the cross-section of any wire produces a voltage, e, around a loop linking such flux in accordance with the equation e=%i) This voltage produces currents which flow in a plane parallel with the axis of the wire and resultin an energy loss. As the load flux is proportional to the load current Ie, and e at any frequency is proportional to 1, the eddy current i is proportional I.. and the total energy loss W=2ei is proportional to I2. Where eddy current losses occur, therefore, they appear, at any fre-4 quency as an effectivezresistance in series with the load, since =R. As these losses are dependent'on frequency, they change with variations in frequency causing changes in the impedance of devices in which they occur. This loss, of course, is not'the loss due to skin effect which is present in an alternating cur-l rent conductor regardless of surrounding flux and currents.
This invention provides for the construction of a transformer whose impedance modifying effect is substantially inde endent of frequency over a wide band of requencies. This transformer has its windings so wound that no substantial accumulation of flux due to load currents is possible at any point within the windin s. For instance, in a balanced auto-trans ormer each half of the shunt winding and the adjacent series winding may be wound as a. parallel pair. In the case of a two-winding transformer, the primary and secondary windings may be wound as a parallel pair. A i
A better understanding of the invention will be had from the following specification taken in connection with the drawings, in which:
Fig. 1 is a schematic representation of a two-Winding transformer embodying the invention;
Fig. 2 is a diagrammatic view of a portion of the transformer of Fig. l1 showing the details of the winding; Fig. 3 isa cross-sectional view showing the relative positions of the turns of the windin s of the transformer of Fig. 1;
ig. 4,'s a schematic representation of an auto-transformer embodyin the invention; Fig. 5 shows a portion o? the auto-transformer of Fig. 4 diagrammatically; and
Fig. 6 is a cross-sectional view showing the relative positions of the turns of the windings of the auto-transformer of Fig. 4.
Before taking up the detailed description of the drawings it might be well to consider briefly the action of a transformer, considering for simplicity a unity ratio transformer. It is well known that the impedance diagram of a transformer includes a shunt element izing current in the primary w ich in a well constructed transformer 1s small 1n comparison with the primary load current and, as to l phase is substantially at right angles thereto. 'Izhe load current in the secondary is substantially equal and opposite to the load current in the primary, and the secondary load flux within the core neutralizes the primary load ilux. p
Outside the core two regions are to be distinguished, rst, the space occupied by 4the conductors and second the remaining space external to the core. If the secondary winding is spaced materially from the primary windinv the load fluxes outside the core are not entlrely neutralized. In particular, if we consider a primary turn which is surrounded at some distance away by a secondary turn it is found that in the space between these two turns the load fluxes are in the same direction and therefore add ,instead of neutralize. It is, of course, this failure of the two load iiuxes to neutralize which accounts for the leakage flux and the leakage im edance.
onsidering now the space occupied by the winding conductors themselves any leakage iiux which interlinks a turn of the winding produces eddy-current losses in the copper. Applicant has found' that in certain uses of a transformer, at least, these eddycurrent losses in the windings themselves are appreciable as has been noted above.
The eti'ects above described for a unity ratio transformer are, of course, present in a non-unity ratio transformer, except that in considering the magnitudes of the load currents the turns ratio must be taken into account.
The transformer structure now to be described in accordance with the invention reduces the leakage substantially to a minimum and also by the disposition of the primary and secondary conductors reduces the energy losses in the conductors which would be produced by the leakage flux.
In the descri tion to follow the same elements in the di erent figures are given identical numbers while the arrows show by their lengths and directions a rou h comparison of the magnitude of the load currents and the direction in which they iiow at one particular instant in the windings of the transformers. It is to be understood that the magnetizing current has been arbitrarily omitted since-its magnitude is small and any eddy current losses due to it appear as a small additional core loss which has no appreciable effect on the impedance characteristic.
The transformer of Figs. 1, 2 and 3 which is moans shown as a non-unity ratio transformer, comprises a core 5, a primary winding 6 with terminals 10 and 11 and a secondary winding 7 with terminals 12 and 13. (It will be understood that either winding can be considered the primary and the other the secondary). l
` Fig. 2 shows the primary winding 6, be-
1nn1n at terminal 10, being wound rst on t e inside of the loops and then returning b conductor 14 and beingv wound on the outside of the loops endin at terminal 11. The secondary windin 7, nin at terminal 13, is wound on t e insi e of tv e loops and terminates at terminal 12. Winding 6, being the high voltage, small current wmding, is shown with twice the number of turns as the low volta e, lar e current winding 7, while 4the lengt s of tl e arrows roughly indicate the comparative magnitude of the currents. The neutralization of the flux roduced by the oppositely directioned loa currents 1s substantiall complete since the current owing in win in 7 is approximatel twice as large as that owing in the win 'ng 6, the winding 6, of course, having twice as many turns as winding 7. The arrangement of the turns is shown in Fig. 3 in cross-section with a turn of windin 6 oneither side of a turn of winding 7. n this last fi ure the dots represent current flow toward t e reader and the crosses represent current flow in the opposite direction in accordance with the wellknown convention. The windings are shown in Fig. 2 as a group of three for clearness but this group may have as many turns as required for the desired voltages and loads.
The auto-transformer of Figs. 4, 5 and 6 comprises a core 20, a primary winding including the upper series winding 21 and lower series winding 22 together with shunt or bridge winding 23, havin terminals 24 and 25, and a secondary win ing including only the shunt winding 23 having terminals 26 and 27.
Tracing the larger current circuit, or in this case, the secondary winding, starting at terminal 27, this circuit be ins at oint 30, Fig. 5, the current flowin t rough t e shunt winding 23, the turns o which are on the outside of the loops to point 31 and terminal 26. The current in theprimary winding flows in series windin s 21 and 22 in the opposite direction from the current in the circult just traced. Starting at terminal 24 the inner conductor shown in the two upper loops of Fi 5 is series winding 21 terminating at point 3l, while the correspondin conductor startin at point 30 in the two ower loops forms t e series winding 22 which terminates at terminal 25.
It is noted that the transformer is so wound that at any oint within the windings there is substantial y no accumulation of ux due to load currents, that is, the product of mesma the number of turns and the load current in one direction tending to cause flux to linkany point is equal to the product of the number of turns andthe load current in the opposite direction causing flux to link the same point. As a result, there is an almost complete neutralization of load flux at all oints.
In the actual winding of the trans ormer as described it is preferable to wind the series and shunt windings as parallel pairs, that is, in the transformer shown in Fi s. 4, 5 and 6, winding 21 and the upper half o winding 23 are wound as one parallel pair, and winding 22 and the lower half of winding 23 are wound as another parallel pair, certain terminals being connected at points 30 and 31 as shown in Fig 5,
The transformers described have been shown as having turns ratios of 2 to 1 but any turns ratio may be obtained by grouping as many wires as desired and in a manner to substantially neutralize the flux at any point within the windings due to load currents flowing in each wire.
Although the invention has been described embodied in two particular transformers it is to be understood that modifications may be made and that no limitations upon the invention are intended other than those imposed by the scope of the appended claims.
What is claimed is:
1. An inductance device for connecting two lines, comprising a core with a plurality of inductively coupled windings, each'of saidk windings having its individual turns carrying current in one direction at a certain instant interleaved with the-individual turns of another winding carrying current in the op-I posite direction at said instant and substantially preventing the flux within either of said windin from producing eddy currents in any of said turns.
2. An inductance device intermediate and connecting two lines having different impedances, comprising a core with a primary windin and a secondar winding thereon inductive y cou led, sai windings having a diierent num r of turns res ectively, said primary winding being con uctively connected to one of said lines and said secondary winding bei other of sai? carryin current in one direction at a certain instant avin each turn interleaved with the turns of sai secondary winding ca ing current in the opposite direction at sai instant to reduce eddy current'losses in said turns.
3. A non-unity ratio inductance device intermediate and connecting two lines having dierent impedances comprising1 a core, a
conductively connected to the lines, said primary windingten other of said lines and inductively coupled to said primary winding carr ing current in the opposite direction at sai particular in- Stant, the turns of said primary and secondary windings bein wound respectively as parallel groups wit the product of the current in one direction and the turns carrying said current tending to cause flux to link a articular point outside the core, substantialy equal to the roduct of the current in the opposite direction and the turns carrying Said ofppositely flowing current tending to cause ux to link said point.
4. In combination, a multi-layer winding non-unity ratio inductance device havin a core and a plurality of windings on sait core, a source of currents of a band of frequencies to be transmitted through said device, and a receiving circuit, each turn of said windings connected to said source being wound adjacent a turn of said windingsfconnected to said receiving circuit, the oppositely flowing load currents in the alternate turns preventing the flux within the device from causing substantial eddy current losses in said turns. y
5. An auto-transformer comprising a lurality of series and shunt windings in uctively coupled forconnecting and matching the impedances of two electrical circuits having `diflerent impedances, each turn of said series windings paralleling and wound adjacent to at least one turn of said shunt windings to neutralize at any point within said windings the flux produced by the load currents in said auto-transformer.
6. An auto-transformerintermediate and connecting two lines having different im edances, comprising a core, a primary win ing lon said core connected to one of said lines substantially equal to t e product of the current in the opposite direction and the turns carying said otppositely ,flowing current ing to cause ux to link said point.
In witness whereof, I hereunto subscribe my name this 15th ttig of Se tember, 1928. BER G. GANZ.
primary winding on said core connected to y,
one of said Alines carrying current in one di- -rection at one particularinstant, and a secondary winding on said core connected to the ius