US3049696A

US3049696A - Magnetic core circuits providing fractional turns

Info

Publication number: US3049696A
Application number: US718887A
Authority: US
Inventors: Hewitt D Crane
Original assignee: Burroughs Corp
Current assignee: Unisys Corp
Priority date: 1958-03-03
Filing date: 1958-03-03
Publication date: 1962-08-14
Anticipated expiration: 1979-08-14

Description

Aug. 14, 1962 H. D. CRANE 3,

MAGNETIC CORE CIRCUITS PROVIDING FRACTIONAL TURNS Filed March 3, 1958 INVENTOR. HEW/77' a (RA/Vt Patented Aug. 14, 1962 3,0495% MAGNETIC CORE ClRClUlTS PROVIDLNG FRACTIGNAL TURNS Hewitt D. Crane, Palo Alto, Calif., assignor to Burroughs Corporation, Detroit, Micln, a corporation of Michigan Filed Mar. 3, 1958, Ser. No. 718,887 3 Claims. (Cl. 340-174) This invention relates to magnetic core circuits, and more particularly, is concerned with the winding of magnetic cores to achieve the equivalent of fractional turns.

In copending application Serial No. 704,511, filed in December 23, 1957, now Patent No. 3,604,244 in the name of Hewitt D. Crane and assigned to the assignee of the present invention, there is described an improved core register having a novel transfer circuit requiring no diodes or other impedance elements in the transfer loops between the magnetic core devices in the register. Information is transferred from one core device to another by means of pulses of predetermined current level. By means of a biasing arrangment on the core devices, as therein described, the range over which this current level of the transfer pulse might be varied without materially affecting the information transfer is greatly extended, and certain other advantages are also achieved.

As further described in copending application Serial No. 698,615 filed November 25, 1957, now Patent No. 2,969,- 524 in the name of David R. Bennion and assigned to the assignee of the present invention, a core register of the type described above can be made with unity turns ratio in the windings of the transfer loops coupling one core to the next core. Moreover, a. core register can be constructed with a single turn linking each of the core elements coupled by the transfer loop in the register. However, if bias is to be utilized to extend the range of the transfer pulse, in the manner described in connection with the first-mentioned copending application, the turns in the transfer loop must be greater than the turns in the bias winding on each of the core elements. This means that if the transfer current is to energize both the transfer loop and the bias winding, the use of single turns in the transfer loop dictates that the bias windings must have less than a single turn, i.e., fractional turns. Of course, in practice, fractional turns as such do not exist.

By the present invention, the equivalent of fractional turns is achieved. This permits a single turn to be provided in the transfer winding, the same current to pass through the transfer winding and the bias winding, and still achieve fewer ampere-turns in the bias winding than in the transfer winding of each core element in the register. As a result, unity turns can be used in the transfer loop, which greatly simplifies the winding of the core elements and gives rise to simplified and less expensive fabricating techniques.

In brief, the invention provides the equivalent of fractional turns on a magnetic core circuit by means of a magnetic annular core including a plurality of laminated layers. The winding providing effective fractional turns linking the laminated core includes a plurality of parallel single conductors, each conductor linking a corresponding laminated layer of the core element. The number of laminated layers of the core element and the associated number of parallel single conductors in the winding is determined by the fractional turn desired. For example, if an effective one-third turn linking the core element is required, then three laminated layers with three parallel conductors in the winding are provided.

For a more complete understanding of the invention, reference should be had to the accompanying drawings, wherein:

FIG. 1 shows a magnetic core transfer circuit with bias;

' of the transfer loop linking the core.

FIG. 2 is a graphical plat of flux switched in a core element as a function of ampere-turns linking the core and is used in explaining the operation of the circuit of FIG. 1;

FIG. 3 is a diagrammatic showing of a core element wound in a manner to achieve the effective fractional turns according to the principles of the present invention; and

FIGS. 4 and 5 show alternative embodiments of the present invention.

As described in more detail in the above-mentioned copending applications, a binary register and transfer circuit can be constructed using basic core elements arranged as shown in FIG. 1. This circuit includes a pair of magnetic

annular cores

10 and 10 made of ferrite or similar magnetic material having a square hysteresis characteristic, i.e., a material having a high flux remanence. A coupling loop 20 links the transmitting core 10 through an output aperture 14 to the receiving core 10' through an input aperture 12'. Transfer of information stored in the transmitter core 10 to the receiver core 10 is effected by an Advance current pulse by means of which a current 1 is applied to the transfer loop 20 in the direction indicated by the arrow. The advance current divides in the transfer loop into a current I passing through the aperture 14 of the transmitting core 10 and a current I passing through the aperture 12' of the receiving core 10.

It can be shown that with the flux in a given core extending in the same direction on either side of the aperture linked by the transfer loop, the current in the branch winding linking the core must exceed a certain threshold level before any of the flux around the core can be reversed or switched. This is shown by curve A of FIG. 2, which shows the relationship between the flux switched in the core with increase of ampere-turns in the portion Ampere-turns must exceed a threshold level T before a substantial amount of flux is switched in the core.

However, if the flux on either side of the aperture initially extends in opposite directions, the current required to switch flux is greatly reduced. This relation is shown by curve B of FIG. 2, which shows that the ampere-turns must only exceed a much lower threshold level T before flux is switched in the core. The reason is that in the latter case, flux does not switch around the core, but only switches locally around the aperture.

This property is used to effect the transfer between the transmitting core and the receiving core. The advance current I is set at a level such that the ampere-turns linking the two cores is below the threshold level T when the cores are both cleared with all the flux in one direction, as indicated by the arrows in FIG. 1. As a result no flux is switched in either core by an advance current pulse. However, if the transmitter flux is initially set with the flux extending in opposite directions on either side of the aperture 14, the ampere-turns linking the core 10 through the aperture 14 will exceed the lower threshold level T, when the advance pulse is applied to the transfer loop 2% As a result, fiux is switched by the transfer pulse in the transmitter core 19. The switching of flux around the aperture 14 increases the impedance to the flow of current I thereby increasing the portion of the advance current I -As a result the ampere-turns linking the receiver core 10 is increased above the threshold level T resulting in switching of flux in the core 16. In this manner the fiux configuration in the receiver core at? is not modified or modified in response to an advance current pulse, depending upon the initial flux condition of the transmitter core it).

As pointed out in the above-identified patent application by Hewitt D. Crane, bias windings may be provided on both the transmitter core 10 and the receiver core 10', as indicated at 22 and 22 respectively. The current 3 through the bias windings is in a direction to oppose the switching of flux in the cores in response to the advance current pulse. The effect is to increase the upper threshold level T thereby permitting the advance current to be greatly increased.

As further pointed out heretofore in the abovementioned patent application, the bias windings 22 and 22' may be connected in series with the transfer loop 26 so as to be energized by the advance current pulse. This has the effect of providing a moving threshold with changes in level of the advance current, so as to provide a self-compensating effect. Since the effective upper threshold T depends upon the amount of bias, any change in the advance current changes the amount of bias and thereby moves the threshold. if the threshold were not moving, an increase in advance current might result in the threshold being exceeded so as to produce a swit ring of flux in the receiver core It) when it was not dean-ed. However, with the threshold moving to a higher level as the result of the increase in bias with the increase in advance current, a greater increase in advance current is required before the threshold level can be exceeded by the advance pulse.

With the circuit arranged as thus far described, the ampere-turns in the bias winding on the transmitter core must be less than hall the ampere-turns linking the aperture 14. Otherwise, the ampere-turns of the bias Winding would exceed the threshold at which flux can be switched around the core 10. This fact has heretofore necessitated the use of multiple turns in the loop linking the output aperture in the transmitting core. To use a single turn would result in the requirement that a fractional turn link the core by the bias winding, since the current is the same in both the transfer winding and bias winding. The present invention achieves the effect of fractional turns in the bias winding.

According to one modification of the present invention, as shown in FIG. 3, each of the core elements in the register, such as the core element lit, is made of a plurality of laminated layers as indicated at 30, 32, and 34, three being shown by way of example only. The transfer loop 20 includes a single turn which links the core element 10 through aligned apertures in each of the laminated layers, forming a single conductive turn linking the output aperture 14.

The bias winding 22 is formed of three

parallel branches

36, 38, and 40. Each of these branches includes a single conductor which links a corresponding one of the laminated layers of the core element through the central opening therein. As a result, the advance current passing through bias winding 22 splits equally between the plurality of parallel branches. It will be seen in PEG. 3 that /3 of the advance current l passes through each of the parallel branches. The net current flowing between the layers of the core is zero, since two parallel branches of the bias winding pass between each layer with current flowing in opposite directions in the two branches. As a result, the effective ampereturns linking the entire core 10 by the bias winding 22 is /sl The effect is that the bias Winding appears to be a third of a turn in contrast to the single turn of the transfer winding 2 3. It should be noted that the bias winding arrangement is symmetrical so that even though there are parallel branch windings, no circulating currents are normally induced in the parallel branch circuits.

The same effect of fractional turns in the bias winding, achieved in FIG. 3 by laminating the core structure, can be achieved also in a solid core structure by providing extra apertures extending through the core material. The apertures may extend radially as shown in FIG. 4, or may extend parallel to the axis of revolution as shown in Pl'G. 5. In either event the resulting portions of the core to which it is divided by A6 apertures, are linked by separate parallel branches constituting the bias winding. Again each of the apertures has two parallel branches of the bias winding passing current therethrough in opposite directions so that the net current flow through the apertures is always zero. As a result, only the fraction of the current passing through one of the parallel branches effectively links the core to provide the effect of fractional turns in the manner described above in connection with PEG. 3.

From the above description it will be recognized that a bias winding having effectively fractional turns linking a core element is provided. By the present invention the transfer loop may include a singie turn linking each core, and the bias winding and transfer loop winding can be connected in series from the same current source, and yet the bias winding can have effectively fewer ampereturns than the transfer loop, i.e., can effectively be a fraction of a turn.

While the invention has been described as including parallel branches of single conductors in the bias winding, the para lei branches may be made with several turns, and the number of turns in the different parallel branches may not necessarily be equal. However, if they are not equal, an unbalance may exist which may produce circulating currents during transient periods in which flux is being switched in the core element.

What is claimed is:

l. A magnetic storage and transfer circuit comprising a magnetic core forming a closed loop magnetic path, a portion of the core defining a plurality of parallel flux paths, a first winding and a second winding linking different portions of the magnetic core, said windings being connected in series with each other across a common current source, the first winding including a single conductor in a single turn linking a portion or" the core, and the second Winding including a plurality of parallel-connected single conductors, each of the conductors linking a different one of the parallel flux paths of the core in a single turn.

2. Apparatus as defined in claim 1 wherein the magnetic core is laminated to form the plurality of parallel flux paths, the conductors connected in parallel to form the second winding linking respectively the laminated layers of the core.

3. Apparatus as defined in claim 1 wherein the magnetic core has a plurality of apertures extending therethrough lying substantially in a common plane extending normally to the magnetic path of the core for dividing the core into parallel flux paths in the regions between the apertures, the single conductor of the second winding extending through respective ones of the apertures to individually link respective ones of the parallel flux paths.

References Cited in the file of this patent UNITED STATES PATENTS 2,600,057 Kerns June 10, 1952 2,889,542 Goldner et al. June 2, 1959 FOREIGN PATENTS 760,048 Great Britain Oct. 21, 1956 1,136,322 France Dec. 29, 1956 1,141,472 France Mar. 18, 1957 1,187,894 France Oct. 29, 1957