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A.C. losses of superconducting Nb-Ti alloy wires were measured by electrical method with alternating electrical current through wires. The losses were measured on various diameter of wires which were chemically or mechanically thined, and it was found that there were no size effects.The losses were measured under the external parallel D.C. magnetic field, and those of commercial fine wires were also investigated. We computed the loss of multi cores wire, form the results obtained from single core wires and compared it with the experimental resuls of fine multi cores wires.The effects of chemical etching and mechanical drawing on the losses are considered in the metallurgical points of view. The losses of Nb-Ti wires in the region of low magnetic field seem to fit Yasukochi's model.

The behavior of an analog memory element using a single toroidal magnetic core with rectangular hysteresis loop is presented. In this element, flux levels stored in the core as analog information can be nondestructively and continuously read out. With the application of a slight, amplitude-modulated, radio frequency (RF) field, the modulation frequency component of the induced voltage waveform is detected as an analog output signal. The principle of operation requires only one core per memory element, so that problems of mismatching of two cores, which appear in a second-harmonic type element, are completely eliminated. Experimental results show that this is suitable as an analog memory element, and that the eddy-current effect enhances the output signals.

In a previous paper Miss Calderwood and the present author examined the losses in the lead sheath of a single-core cable when carrying an alternating current, and concluded that, provided the outgoing and return cables were laid within a certain limiting distance of one another, no difficulty would arise due to eddy currents in the sheaths at normal frequencies. In the present paper this work is extended to cover the case of single-core cables that are both lead-covered and armoured. A theoretical investigation of the reactances and losses is carried out and is checked against the actual test figures obtained by Harvey and Busby. It is shown :- 1. That the flux in the armour, the reactance due to that flux, and the appropriate hysteresis and eddy losses can all be approximately predetermined. 2. That for low-tension transmission, lead-covered and armoured cables are impracticable with armouring as at present constructed. 3. That the use of such cables for e.h.t. transmission is not precluded by the magnetic conditions introduced by the armour, and consequently such cables are practicable. There would, however, be some difficulties to be overcome due to large capacity currents when the transmission distance is great.

A REVIEW of the literature concerned with magnetic amplifiers has disclosed a myriad of articles dealing with the load circuit and sometimes control circuit response of single-core amplifiers employing the self-saturation principle.1?4 Each of these discussions has utilized specific assumptions which are in each case aimed toward an ultimate simplification of the mathematical manipulations which finally lead to the required response. In many cases the predicted magnetic amplifier response suffers because of the assumptions thus used.

The controversy as to the calculation of sheath circulating-current losses is referred to, and single-phase tests are quoted to show which formulae agree best with actual measurements. Formulae for the circulating currents in three single-core cables with either horizontal or delta spacing are developed and experimental results are given to show how these agree with the values calculated from the formulas.

The paper is intended to form a corollary to that of Professor Cramp and Miss Calderwood † and deals with the losses involved in the distribution of alternating currents in sheathed cables in which the sheath is of magnetic material. Single-core rubber-insulated cables, each enclosed in a separate iron tube, and also single-core cables armoured with one or two layers of galvanized iron or steel wires, are dealt with, and experimental data are given showing the measured losses in each case. It is shown that, while the losses due to induction in a tube are considerable, those in a wire-armoured cable are comparatively very small, and also that the distance separating the individual cables forming a circuit has very little effect in determining the losses involved. In the case of the wire-armoured cable, also, the connection of the sheaths of separate cables so as to form a closed sheath circuit has no appreciable effect upon the losses, and the current which will flow in such a circuit is so small as to produce no considerable heating.

The accurate practical determination of inductive losses in an a.c. system of single-core lead-covered cables is considered in detail, and test-results which are correlated with calculations are quoted by way of illustration. Bridge methods have been developed for the measurement of both the total and individual losses in single-phase and 3-phase single-core systems. These methods are shown to be capable of great accuracy. The feasibility of armouring single-core cables has been discussed by various authorities, whose opinions are widely divergent. A series of tests has been carried out, the main results of which are given herein. These show clearly the practical limitations imposed by the inductive effects from armouring each cable separately with wire armour. They also provide a sound empirical basis from which the losses in any given system may be estimated.

This paper describes the behavior of a transformer having a plurality of windings mounted on a single core, and discusses applications in the automatic computation of linear algebraic expressions such as simultaneous equations and the like. The computing circuits are superior to prior ones in that they combine the following properties: they contain no amplifiers, or components of limited life such as vacuum tubes; they require no iteration, either manual or automatic; and they bear a close pictorial resemblance with the equations to be solved, thus simplifying the operating procedure. Actual experimental results are given for a set of simultaneous inequalities such as occur in linear programming theory; this includes the solution of several sets of simultaneous equations.

It is frequently a matter of convenience to use single-core lead-covered cables for transmitting power by means of alternating current, and in such cases the magnitude of the loss arising from the eddy currents induced in the lead sheath becomes a matter of importance. Recently some power-supply authorities have refused to connect to their lines any distributing system depending upon the use of such cables.The eddy losses in the sheaths of these cables may be divided into two groups, called herein “sheath eddies,” and “sheath circuit eddies.” The latter occur only when one or more cables have their sheaths connected at more than one place.The losses are analysed for a single cable, a pair of single-phase cables, and a set of three-phase cables.It is shown that the sheath eddies are in all cases negligible, and that the sheath circuit eddies may be kept within reasonable limits by proper regulations regarding the spacing of the cables.It is suggested that the I.E.E. Wiring Rules should contain such regulations, and that so long as these are adhered to there is no justification for refusing to connect single-core lead-covered cables to any ordinary a.c. system. The necessary data are given for the framing of the regulations.Similar questions arise regarding armoured cables. The results in this case are awaiting the conclusion of the experiments now being carried on at the University of Birmingham.

A simple experiment on a magnetically-balanced circuit, consisting of a flux source and two equal-length parallel paths is outlined. It is observed that if a controlling signal causes one of the parallel paths to be preferred and this controlling signal is removed before switching is completed, the parallel path originally preferred continues to be preferred. The core equivalent of a balanced circuit is then examined to determine if this phenomenon is present there as well. It is found that the basic behavior of a balanced circuit and its core equivalent can be made the same, provided care is taken in setting up the same initial conditions in both circuits. It is shown that initial flux levels are important, as well as the rate at which these initial levels are established. An attempt is then made to relate, in a qualitative way, the circuit properties observed to known properties of a single core. It is observed that the properties which will be exploited here are present in most standard materials; however, a balanced circuit tends to exaggerate these properties. In Section II experiments on two balanced circuits interconnected with a 1:1 turns ratio coupling winding are described. This configuration has been found to have two stable states, the final state being dependent on the initial condition in one of the elements. Signal amplification has been achieved over at least a 4:1 range of drive currents. These results are readily explainable by reference to the element characteristics described in the first section.

The delay unit for digital filters can be realized with hardware in either of two ways, i.e., the analog and digital types. If accuracies between 0.1 and 1 percent are required, then it is known that the analog methods simplify the construction of the digital filters. This paper presents the delay unit for the digital filters using a single core which circumvents the problem of core matching. The magnetic delay unit has essentially no practical limitation on the long delay time. Therefore, the digital filters for very low frequencies can be easily realized. The characteristics of the core material to be required for such a unit are discussed and a method of practical realization is shown. In the practical unit, the delay time of 1 hour is realized without trouble. As to the relation between the input and output signals, an accuracy of within approximately 0.05 percent can be maintained when the whole supply voltage is changed by ±4 percent. Under the conditions of the temperature change from 20 to 50°C, there appears no drift caused by the change of temperature. For large variations of time during 24 hours, the drift is not observed experimentally, so that the above mentioned accuracy can be maintained. These facts show that the delay unit is fairly stable and reliable. As an example of a digital filter to be realized for the noise rejection, the simple first-order low-pass filter has been constructed by the method of the bilinear transformation.

THE magnetic amplifier and magnetic devices in general have garnered an enviable reputation for reliability and maintenance-free operation1 in their not-so-short history.2 For these reasons these devices have been a subject of considerable interest3, 4 to the computer field wherein electron tube failure is a major headache. There have been many magnetic devices developed for use in this field, but for the most part they either have been slow (requiring several cycles of excitation frequency for build-up of output) or have not exhibited any considerable power gain. Speed of response is quite important for this determines computing speed. Power gain is quite important, for in a given computer these devices must be cascaded so that one device operates others as well as associated registering or indicating devices.

Constantine* describes a novel load-sharing matrix switch in which the input winding pattern allows the selection of a single core, while ideally all other cores have zero net excitation. These patterns realize 2 n−1 outputs with 2 n inputs, the inputs being grouped in 2 n−1 complementary pairs

Push-pull magnetic amplifiers using a single core are known for circumventing the problem of core matching, but these amplifiers have the following drawbacks: the extreme reduction of gain with the decrease of input resistance, low output power, etc. These problems can be solved by using two magnetic circuits of a stacked four-legged core structure as twin cores in the full-wave type of self-saturating magnetic amplifier. Experiments show that it is possible to obtain twin cores sufficiently well matched, because each leg is from the same sheet, and to decrease the thermal resistance between the twin cores by the yoke connecting between them. As a result it is evident that the use of a four-legged core can improve the zero drift caused mainly by the change of ambient temperature. With this four-legged core structure, the input magnetomotive force equivalent to the zero drift caused by the change of ambient temperature can be decreased by at least one order of magnitude, as compared with spiral core pairs.

Magnetization measurements performed on three types of Nb–Ti superconducting composite wire have shown that twisted multistrand wire not only is very stable but also has the smallest magetization and thus is the most suitable for ac applications.

The conditions which govern the eddy currents in the lead sheaths of a pair of single-core cables undergo a change a s the sheaths are moved from the position of intimate contact. The consequent changes in e.m.f. and eddy losses have been the subject of considerable discussion. The following notes record an attempt to settle the matter experimentally by tests on a cable with a Drysdale potentiometer. The conclusions reached are that while the sheath circuit e.m.f. appears to be proportional to log d/r, the change in the losses as this ratio passes through the value 2 is rendered indeterminate by other variables which cannot be separately measured.

New square-loop ferrite toroids were developed especially for NDRO memories with permeability sensing. They are 20-mil cores (outer diameter) with a coercive current of 80 mA. The information 0 is written by a short but high set pulse of uncritical amplitude (about 1000 mA). To write the information 1 in a selected address, the concerning core must be demagnetized in a coincident current mode. Applying a read pulse with an amplitude of 50 mA and a rise time of 5 ns results in a peak voltage for a single core of about 2.5 mV in the 0 state and about 7 mV in the 1 state. In a plane a two-core-per-bit system will be used so that bipolar sense signals appear.

A review of installation techniques has been undertaken for single-core power cables employed in the cable networks of industrial plant. Particular attention has been given to the performance of trefoilcable groups under short circuit, and the influence of the consequential electromagnetic forces on the supporting and securing system used to hold the cables. For the investigation, a series of short-circuit tests have been carried out, subjecting a range of typical cables to currents up to 44 kA. Based on these tests, proposals are made for securing cables using ties at spacings chosen over a range 0.3 m-1.2 m, with cleats spaced at 4 m and main supports at 2 m.

A brief outline of the theory of the lapping operation for high-voltage single-core paper-lapped cable is given, showing the stability conditions which the insulation thickness must satisfy in order that bending of the cable on the reel or capstan does not cause any damage to the insulation itself. An example of the design of a high-voltage cable is considered, showing the application of the theory outlined and its practical use.

A REVIEW OF THE literature concerned with magnetic amplifiers has revealed a multitude of articles dealing with the load circuit and sometimes control circuit response of single-core amplifiers employing the self-saturation principle. These discussions all have utilized specific assumptions which in each case were aimed toward an ultimate simplification of the mathematical manipulations directed toward the solution of the required response. In some cases the assumptions are valid; however, the general case of magnetic amplifier operation often suffers because of the specializations thus used. It therefore seems worth while to consider a rigorous mathematical analysis based upon the existence of finite forward and reverse rectifier resistances as well as a flux-current loop of finite area and finite slope.