Showing papers in "Journal of the Institution of Electrical Engineers in 1953"

An investigation of the characteristics of cylindrical surface waves

Abstract: Some quantitative measurements on cylindrical surface waves have been made at a frequency of approximately 10 000 Mc/s. For this purpose an axial standing-wave indicator and an instrument for determining the radial field distribution have been designed and tested by application to a wave of known configuration. The axial standing-wave indicator was used for simple impedance measurements and is now established as a practical device. A series of quantitative observations on cylindrical surface waves have been made with the instrument for examining the radial field distribution, which at a long distance (say 30 ft) from a launching horn, was found to agree with that expected from theory. In the case of thin bare copper wires and enamelled wires of small size the radial decay coefficient deduced from the field-distribution graph approximated closely to the value obtained from the Sommerfeld-Goubau theory. On the other hand, the field distribution in the vicinity of the horn was always considerably distorted by radiation from the horn.For accurate work in the limited space available, it was found necessary to dispense with the horn and set up a surface-wave resonator. This arrangement is capable of yielding the same information on field distribution, since the standing-wave and travelling-wave patterns are identical. The wavelength of the surface wave supported by the resonator at its resonant frequency was measured by a special method described in the paper, and from a knowledge of the resonant frequency the decay coefficient was calculated.Measurements on No. 24 S.W.G. copper wire thickly coated with polythene showed that the corresponding values of the decay coefficient derived from the Goubau approximate theory were greatly in error. This applied in particular to conductors having a coating of polythene whose thickness exceeded 0.010 in. A curve relating the coating thickness with the measured decay coefficient was obtained and compared with the Goubau predictions. Later the assumptions made in the original theory were revised, and accurate curves displaying the dependence of the decay coefficient on the thickness of dielectric coating, wire diameter and frequency were computed. These curves were found to be in agreement with the experimental results.The surface-wave resonator can also be used for the measurement of surface reactance of corrugated surfaces.

An improved scanning electron microscope for opaque specimens

Abstract: A brief survey is given of the methods of examining opaque specimens in the electron microscope. The principle of the scanning electron microscope is described and mention is made of previous instruments. The design of such microscopes is discussed and the theoretical limit on performance is determined. The optimum scanning-beam voltage, beam current and scanning speeds are given. A recently built electrostatically focused scanning electron microscope for opaque specimens is described. This microscope has several new features, including: (a) The use of high-energy electrons to reduce the effects of surface contamination of the specimen. (b) Oblique scanning of the specimen, so that the image contrasts are formed by the topography of the etched surface of the specimen. (c) Direct amplification of the electron beam with an electron multiplier having beryllium-oxide-coated dynodes. (d) Direct viewing at low magnifications on a cathode-ray tube with a long-persistence screen, and photographic; ecording from the screen at high magnifications. Examples of micrographs of aluminium taken with the instrument are included and these show a resolution of about 500 A. It is concluded that higher resolutions could be obtained with this instrument if improved magnetic shielding and astigmatism correction were to be incorporated. Some measurements on the reflection of high-energy electrons are described in an Appendix.

A new approach to the design of super-directive aerial arrays

Abstract: The current distribution required for maximum directivity of an array with a finite number of elements and any specified geometrical configuration is shown to be completely defined by the self- and mutual resistances of the elements and by a certain component of the voltage (the “resistance voltage”) across the terminals of each element. This voltage component is required to vary from element to element in the same way as the instantaneous local values of a sinusoidal disturbance travelling across the array, in the direction under consideration, with the velocity of an electromagnetic wave.As a consequence, the maximum gain of the array is expressible either as a double sum containing only the mutual conductances between the individual elements multiplied by trigonometrical factors depending on their spacing, or as an expression identical (except for a numerical factor) with that for the distant field of the array.These theorems hold, slightly modified, for arrays of non-identical elements.The theory has been applied to the numerical calculation of certain simple arrays. It appears that, for arrays of a given size, directivities greater than those obtained by conventional design methods can be achieved without excessive losses.This has been substantially confirmed by an experimental array of four elements operating at 75 Mc/s. The theoretical gain was 10.1 db, while 8.7 db was measured. Of the discrepancy, 0.6 db was calculated to be due to losses in the feeder system and a further 0.2 db to losses in the dipoles. The bandwidth was about ±½ Mc/s for a drop in gain off ½ db. The degree of super-directivity is indicated by the fact that a physically identical array fed with equal-amplitude currents phased for maximum field strength in the end-fire direction would have a gain of 4.6 db.

The solution of passive electrical networks by means of mathematical trees

Abstract: A new method of solving electrical networks is described which is more rapid than the classical determinant method. The new method is based on the properties of certain sub-networks termed ?trees? and ?2-trees.?. It is shown that, with suitable algebraic representations, the required sets of trees and 2-trees can be evaluated with the aid of equations in which the terms are networks. Functions known as linkages are defined in terms of sets of trees and 2-trees, and it is shown that these functions obey laws analogous to Kirchhoff's laws for voltages and currents. Hence relations involving voltages and currents can be expressed in terms of linkages. In particular, the transfer admittance of a network can be expressed as the ratio of the set of all trees on the network to an appropriate linkage. Network theorems can be rapidly deduced with the aid of trees and 2-trees. Since the method gives results in terms of admittances, a rule is given whereby admittance functions can be transformed into the corresponding impedance functions.

The properties of artificial dielectrics comprising arrays of conducting elements

Abstract: Part 1 of the paper describes a theoretical analysis of the effective permittivity of arrays of perfectly conducting elements of simple geometric shapes—e.g. cylindrical rods, thin strips, spheres and discs— and the results of a supporting experimental investigation on arrays of metallic elements of these shapes at a frequency of 1 000 c/s. Dielectric media of this type are being used for the construction of centimetre-wave lenses. It is shown that representation of the elements as simple dipoles is inadequate at high concentrations and that account must then be taken of higher-order multi-pole interaction between them. Where evaluation of the latter has proved practicable, the experimental and theoretical permittivity values are found to be in close agreement over the whole range of concentration investigated.Part 2 describes an experimental investigation of the permittivity and dielectric-loss characteristics over the frequency range 400–10 000 c/s of a cubical array of spherical elements composed of imperfectly conducting material as a function of the concentration of these elements, and discusses the results in terms of the theoretical analysis given in Part 1. This investigation is an extension of earlier studies of the behaviour of composite dielectric materials.

A General Method of Analysis of Three-Phase Induction Motors with Asymmetrical Primary Connections

Abstract: It is demonstrated that a systematic application of the theory of symmetrical components to the phase quantities of a symmetrically-wound induction motor provides a general method of analysis which can be used to predetermine the performance characteristics of the motor for any form of asymmetrical primary connection. Among the particular forms of asymmetry considered in some detail are abnormal connection of the primary phases and the insertion of asymmetrical line impedances or auto-transformers.It is noted that discrepancies in published work on the subject are due to ignoring the presence, or incorrectly assessing the effect, of the zero-sequence system; this system is therefore given special attention. Experimental results confirm the validity of the general method.

Breakdown of insulation by discharges

Abstract: The principal factors limiting the safe working electric strength of modern low-loss insulation are electrochemical deterioration and breakdown caused by internal or surface discharges. In the paper the mechanisms of deterioration and breakdown by discharges are discussed in detail. Special consideration is given to the effects of the amplitude, frequency and waveform of the applied voltage on the discharge sequence and on the rate of dielectric deterioration. Suggestions are made for supplementary industrial tests to assess the resistance of materials to internal and surface discharges.

Operating characteristics of salient-pole machines

Abstract: By using the well-known 2-axis theory of Blondel the paper develops on a simple geometrical basis the steady-state characteristics of synchronous salient-pole machines. From these it is shown that appreciable economies can be realized by relating the short-circuit ratio, and thus the synchronous reactance, of an alternator to the stability characteristics required by the load. It is also shown that further economies can be obtained in both alternators and synchronous condensers by designing the excitation system to supply positive and negative field currents. Power-station operation can be simplified and made more reliable by the use of a combined watt- and VAr-meter with a dial based on the power chart evolved in the paper. The common basis underlying the operation of the salient-pole alternator, synchronous motor and condenser, and synchronous reluctance machine is shown by a simple generalized diagram, and the operation of these types of motors is briefly discussed. Equations are evolved for determining machine characteristics with greater accuracy than is given by the geometrical method.

The reflection and absorption of radio waves in the ionosphere

Abstract: A brief historical review is given of the investigations on the absorption of radio waves made in the United Kingdom since 1935 together with a detailed discussion of the factors which must be considered when making accurate measurements of this phenomenon. An outline of the theory of ionospheric absorption and its application to practical absorption measurements is included. The effects of double refraction, polarization, spatial attenuation, dispersion, ionospheric inhomogeneities and partial reflection, which modify the apparent attenuation of radio waves reflected in the ionosphere, are discussed. The methods used to minimize errors due to these factors are presented in detail. The experimental techniques used in the routine absorption measurements are described fully. The detailed results of the measurements of the absorption of radio waves in the ionosphere, conducted in South-East England during the years 1935 to 1948, are being published separately.

Some Possibilities for the Compression of Television Signals by Recoding

Abstract: The paper describes first the excessive redundancy in television signals, using the term in the sense of communication theory. The information in a picture is largely contained in the edges and boundaries, but in practice these occupy a very small part of the total area. The unequal probabilities of signal elements lying in boundary and smooth surface regions are considered, together with the transition probabilities between adjacent elements. Compression is shown to be possible by making such probabilities more nearly equal, using a system of recoding. Such recoding may be achieved by a variable-velocity scanning system if the scan velocity is made high for all regions of the picture having low picture-detail and low for regions having high picture-detail. Picture-detail is defined precisely and measured values are given from observations on working programme material. Finally, compression is shown to be theoretically attainable in both the vertical and the horizontal directions. Correlation between successive line-scan waveforms is interpreted in terms of transition probabilities, and again a redundancy is seen to exist. Suggestions are made for reducing this by storage of every successive frame and scanning alternately in the horizontal and vertical directions, in both cases using a variable-velocity system. Finally, the paper should not be read as describing an existing working system, but purely as a discussion of possibilities.

Waveguide Attenuation and its Correlation with Surface Roughness

Abstract: Measurements of the attenuation produced by air-filled drawn waveguide tubing have been made at a frequency of 9375 Mc/s. The theoretical and experimental performances of various waveguide surfaces are compared and discussed. Detailed studies of the roughness of the internal surfaces of certain standard commercial waveguides have been made, to determine the orders of magnitude of the irregularities and to try to set up a correlation between measured and calculated attenuation values. It is concluded that the discrepancies between these values are due solely to surface roughness, and it is doubtful whether further improvements in surface finish over that of present precision-drawn tubes are required for any applications at frequencies near or below 24 000 Mc/s. The effects of small changes in waveguide dimensions on attenuation, together with the problems involved in measuring both the attenuation and d.c. resistivity of a waveguide sample, are considered.

Electric breakdown of transformer oil

Abstract: A research programme has been commenced which is designed to determine the mechanisms of electric breakdown in insulating liquids under various conditions. The paper describes experimental equipment and techniques, and some results which have been obtained on transformer oil.Special equipment includes a transparent pressure chamber with an internal glass test-vessel, which enables the liquid under test to be subjected to hydrostatic pressures up to 500 lb/in2 and voltages up to 100 kV peak. A protective circuit hasbeen developed, incorporating triggered spark-gap, which limits the duration of breakdown currents to a few microseconds.A wide range of breakdown strengths has been obtained, varying from 5 000 kVpeak/cm with 1-microsec impulses, to below 100 kV(r.m.s.)/cm for a fibre contaminated oil under a.c. test conditions. The removal of fibres raises the a.c. strength of otherwise untreated oil to 400 kV(r.m.s.)/cm.It is concluded that a breakdown mechanism initiated by cavitation is operative in certain circumstances.

Some researches on current chopping in high-voltage circuit-breakers

Abstract: The mechanism of arc extinction in circuit-breakers is discussed. Records of voltage, current, and arc resistance near current zero for an air-blast circuit-breaker are given to illustrate the process and to show how the current may be brought to zero prematurely.Sudden changes of arc resistance are shown to occur near current zero, when the r.m. s. current is low, as for unloaded transformers or shunt reactors, and the way in which these can give rise to current oscillations and sudden interruption of current (current chopping) is illustrated. It is shown that this process is affected by the circuit capacitance and by the circuit-breaker characteristics.The process of current chopping may give rise to high voltages across the shunt reactor or transformer, and the way in which such voltages can be limited by restriking of the circuit-breaker gap is illustrated for both air-blast and oil-break circuit-breakers. Ways of estimating the limiting effect of these gaps from the electric strength of circuit-breaker contact-gaps are given.Comparison of three-phase site conditions and test conditions is made, and limitations of the latter are pointed out.The relation between switching voltages and r.m. s. magnetizing current is studied, and it is concluded that the switching of unloaded transformers gives lower voltages than the switching of shunt reactors. Suitable ways in which the voltage across a shunt reactor may be reduced are described.

Alternating-Current Resistance Standards

Abstract: The basic design principles for resistance standards having a resistance differing from the nominal value by less than 0.01% and a phase angle of less than 0.0001 radn at frequencies up to about 20 kc/s are described. The new nickel-chromium-aluminium alloys, on account of their small change of resistance with temperature, appear to be suitable for standards which must be operated with a considerable temperature rise owing to self-heating. Formulae are given for calculating the residual inductance of standards of various types. A one-ohm standard having a calculated phase angle of less than 0.0001 radn at frequencies up to 30 kc/s is described.

Some mechanisms of insulation failure

Abstract: The paper reports recent investigations into mechanisms of insulation failure. After a review of recent progress emphasizing that failure depends on a number of distinct factors which can be separated by suitable techniques, experimental results are given covering some theories recently established. These include: (a) Electrochemical attack on capacitor dielectrics, with results of life tests on capacitors stabilized with a hydrogen acceptor. (b) Discharge inception in oil-impregnated paper insulation, with results showing that the inception voltage is raised by addition of a hydrogen acceptor to the oil. (c) Failure in thin polystyrene films due to the action of oily particles. (d) Local thermal instability in high-permittivity ceramics due to stress concentration at electrode edges. At least five general causes of failure are now clearly distinguishable, and there is strong evidence for two others which are under investigation. The conclusion is drawn that working stresses in insulation can usually be increased when the cause of failure is known in detail and the design modified accordingly. Attention is drawn to the need for close collaboration between laboratory workers investigating causes of failure and design or development staff.

A survey of present knowledge of thermionic emitters

Abstract: In Sections 1 and 2, after an account of factors influencing the work function of metals, values are quoted and the usefulness of a number of metals as practical thermionic emitters is discussed. The effect of adsorbed films is described in Section 3 and illustrated in connection with emitters with monatomic layers of thorium, caesium and barium. The emission from compounds, and in particular from semiconductors, is considered in Section 4. Sections 5 and 6 deal with the behaviour of certain metallic borides and carbides. Some of these, such as lanthanum boride and thorium carbide, are likely to be valuable as practical emitters. The general properties of oxides are discussed in Sections 8 and 9, where the groups in the periodic table are compared. The barium-strontium-oxide type of cathode is treated in Section 10. This is the most important practical cathode, and the behaviour and limitations are dealt with in some detail. Section 11 describes the performance of thoria as a thermionic emitter.

The Measurement of the Phase Velocity of Ground-Wave Propagation at Low Frequencies over a Land Path

Abstract: The paper describes the measurement of the change of phase with distance of a 127.5-kc/s wave over a particular inhomogeneous land path and the deduction of the mean velocity.The measuring system made use of transmissions from stations of the English chain of the Decca Navigator System, and the path studied was that between the Lewes (Sussex) and Warwick stations (177 km). With the aid of a mobile phase-measuring equipment the difference between the phase of the signal from one transmitter and that of the signal from the other transmitter was measured with an accuracy of 0.25° at 25 points along the path. From these results and a knowledge of the exact position of the points it was possible to plot a curve showing the deviation of the measured phase from that calculated on the assumption of a velocity equal to that in free space.The mean velocity deduced for the path was 299 230 ± 12 km/sec.An examination was made of the measured change of phase along the path in relation to the profile and geological structure. Although there was no definite evidence of the phase of the wave being affected by the ground contours, the influence of the nature of the soil was very marked. A detailed study of the geological structure was undertaken and the electrical characteristics of each section of the path were assessed. A high velocity over ground of good conductivity and a low velocity over ground of poor conductivity was clearly shown.Comparisons between the measurements and the phase changes derived by a method based on theoretical curves of phase lag over homogeneous ground showed good correlation. They also confirmed the theoretical predictions of a characteristic phase disturbance at the boundary between sections of differing conductivity. It is concluded that this method of phase determination over an inhomogeneous path is one which offers a good approximation to the phase changes actually taking place.

The Reproduction of Signals recorded on Magnetic Tape

Abstract: The conventional analysis of the action of the ring reproducing head is re-examined and experiments are described which demonstrate divergences between the theoretical and practical results The action of a reproducing head consisting of a single loop of non-magnetic conductor is analysed and experimental results which verify the theory are given The effects of various common imperfections and maladjustments in all the types of reproducing head are predicted and checked by experiment The findings are then applied to the problem of frequency-characteristic calibration, and the corrections which are necessary to obtain consistent results with various heads are ascertained The practical aspects of standardization are discussed, and the possible application of special heads in this and other roles is noted

A wide-band waveguide phase-shifter

Abstract: A method is described of constructing waveguide phase-shifters well matched over a broad frequency band. The principles of design are discussed, and details are given of the performance of experimental S-band models having bandwidths of 10-25%.

A small sensitive magnetometer

Abstract: A magnetometer is described which was designed primarily for measuring a magnetic field within the confined space of a permeameter. The measuring head of the instrument contains a thin solenoid through which a direct current is passed, to balance the field being measured and produce zero field in the solenoid. A sensitive field detector within the solenoid consists of a fine ferromagnetic (Mumetal) wire carrying an alternating current of frequency 5 kc/s. This current develops a saturating circular field in the wire and causes its effective longitudinal permeability to alternate at twice the frequency of the current. A field along the wire thus produces an alternating induction in the wire and consequently an alternating e.m.f. in the solenoid; this e.m.f. therefore serves as a sensitive indication of field.With associated equipment designed especially for the magnetometer it is possible to detect a change in field strength of 2 × 10−5 oersted. Alternatively the head can be used with standard laboratory equipment allowing a field of 2 × 10−3 oersted to be detected. The maximum field strength that can be measured is limited to about 50 oersteds by the heat developed in the solenoid by the balancing current.

The accurate mapping of electrical fields in an electrolytic tank

Abstract: An investigation has been made into certain errors arising in electrolytic-tank systems used for field plotting. A new technique utilizing square-wave excitation and liquid probes is presented. An assessment has been made of the relative merits of various electrode-electrolyte combinations for practical use.

Some experiments on positive point-to-plane corona and spark breakdown of compressed gases

Abstract: A test pressure vessel for the investigation of electrical discharges in gases at pressures up to 1 000 lb/in2 is described. The electrical insulating properties of compressed air, nitrogen, dichlorodifluoromethane (commercially known as Freon 12 or Arcton 6) and sulphur hexafluoride, as well as certain mixtures of these gases, are compared; a hemispherically-tipped point-to-plane electrode configuration and direct voltages were used. Pronounced maxima obtained in the spark-breakdown-voltage/gas-pressure characteristics for the electronegative gases and gas mixtures are shown to be associated with the establishment of corona at the anode. Corona-current/voltage characteristics for some of the gases tested are included.

Digital computers at Manchester University

Abstract: The new universal high-speed digital computing machine now working at the Computing Machine Laboratory, Manchester University, is described. It has a high-speed storage capacity of 10 240 binary digits and an intermediate storage capacity of over 280 000 binary digits. Its other features include a completely automatic transfer system between the two types of store; a B-tube which allows instructions to be modified in a much shorter time than by normal accumulator use, thus facilitating the programming of iterative processes; and a fast multiplier which carries out a multiplication in the same order of time as the normal addition or subtraction operations. Input and output operations in this machine utilize normal 5-hole teleprinter tape. Input is by way of a photoelectric reader and output can occur either from a tape punch or a teleprinter, or both can operate together. The method of maintenance and also some reliability figures are given.

The propagation of surge voltages through high-speed turbo-alternators with single-conductor windings

Abstract: After a brief review of previous work on the propagation of surge voltages through machine windings, the fundamental differential equations for the propagation of waves through a winding with two coil sides per stator slot are derived. These show that all component frequencies of an incoming wave below a certain critical frequency are propagated through the winding with velocities which are dependent on the frequency. For super-critical frequencies the winding behaves as a condenser whose capacitance diminishes with increasing frequency. Various modes of winding are discussed, together with their effects on the impulse-voltage distribution. Test results on a typical machine are described and the voltage distribution explained with the aid of the fundamental theoretical deductions. The surge impedance of a large 11-kV alternator is about 80 ohms. Evaluation of the inductance for one of the machines tested shows that the majority of the flux produced by the surge current surrounds both conductors in the slot and must therefore be carried by the iron. This is also borne out by the fact that the removal of the rotor decreases both the self and mutual inductances of the windings, owing to the increased reluctance of the flux path.

The wear of carbon brushes at high altitudes

Abstract: The carbon brush depends for its frictional properties on atmospheric water. At high altitudes, where the atmosphere is very dry, friction is high and wear rate is catastrophic. Laboratory apparatus for the study of the phenomenon must simulate the conditions in the upper atmosphere. Conventional lubricants are unsuitable on account of their effect on the electrical contact and their failure to withstand the conditions at the rubbing face. Effective inorganic lubricants give immunity by building up a stable film on the commutator surface, but they adversely affect machine performance.

Transformer-analogue network analysers

Abstract: The paper deals with the use of voltage transformers as multipliers for complex quantities and describes how they may be used to form a network analyser. The analyser consists of a measuring section and a number of identical panels each containing two multiplying units. These panels may be used to represent impedances, admittances, voltage or current sources, phase-shifting auto-transformers or mutual inductances. Valuable features of the analyser are the ease with which negative resistance and unilateral mutual inductance may be introduced. The accuracy of the analyser depends on the suppression of amplitude and phase errors in the voltage ratios of the transformers, and each transformer is supplied with the required exciting current from special compensators. The paper concludes with examples of the principles to be adopted in applying the analyser to common problems concerning the behaviour of power networks, electrical machines and closed-loop control systems as well as to the solution of linear simultaneous equations.

The Double 3-Phase Rectifier with Inter-Phase Reactor excited from a Frequency Tripler

Abstract: The regulation curve of a double 3-phase mercury-arc rectifier is characterized by a sharp fall in the output voltage as the load current increases from zero to a value about twice that of the peak magnetizing current of the inter-phase reactor. Over this current range the mode of operation of the rectifier changes; at no load each anode fires in turn, in a manner typical of a 6-phase rectifier, but when the load current is just sufficient to magnetize the inter-phase reactor, double 3-phase operation of the rectifier commences. To reduce the no-load voltage rise, which in some rectifier applications cannot be tolerated, one of the more satisfactory methods is to excite the inter-phase reactor from an auxiliary source. It is shown in the paper that, by using a frequency tripler as a source of auxiliary excitation, a tenfold reduction is obtained both in the no-load voltage rise and in the critical load current at which double 3-phase operation commences. The variation of the rectifier no-load voltage rise with the phase and magnitude of the frequency-tripler output voltage and with the alternating supply voltage is also deduced.

The Influence of some Head and Tape Constants on the Signal recorded on a Magnetic Tape

Abstract: With recording heads of conventional design, the distribution of magnetization through the depth of a recorded tape may be markedly non-uniform to an extent depending upon the h.f. bias setting. An analysis of this effect is shown to be of value in explaining several aspects of recording performance, including the anomalous loss of high-frequency response commonly observed when using large values of h.f. bias. An analysis of the self-demagnetizing fields created within a recorded tape is also given, and an attempt is made to relate the losses these introduce into the high-frequency performance of the system to the dimensional and magnetic constants of the tape.

Recent advances in cathode-ray-tube storage

Abstract: The paper is essentially in three parts. The first part deals with current practice at Manchester University, and, in particular, with modifications to the defocus-focus system of storage and the signal amplifier. The second part deals with experimental work directed towards the clarification of the mechanism of storage. The third part expounds a qualitative theory based on the experiments described in the second part. Experiments have been performed to obtain information relevant to the following controversial points: (a) The existence of electron-cloud pulses. (b) The effect of variation in the speed of the edges of the cathode-ray-tube grid waveform. (c) The mean potential of the cathode-ray-tube screen surface. (d) The depth of a well. (e) Possible variation of well depth with beam current. It is concluded that storage operation may be theoretically explained by drawing an analogy with a triode valve; the collector, the bombarded spot and the surrounding screen surface being analogous to the anode, cathode and control grid, respectively. For technological purposes the original theory1 may well be sufficient, and it is shown that it can be used to predict storage results.

The Frequency Tripler

Abstract: The most common form of static frequency tripler consists of a 3-phase transformer operated at a fairly high flux density, with an open-delta secondary connected to the triple-frequency load. The nonlinear property of the B/H characteristic of the core material is used to obtain the frequency conversion, and the unwanted fundamental component is removed by the method of connection. There is no theoretical reason why such a frequency tripler should not be designed starting only with the magnetization curve of the core material, but to do this is exceedingly tedious. A more practical approach is to abstract the required information experimentally and present it in a manner convenient to the designer. A series of tests were performed to obtain the information necessary; the cases investigated included pure resistive loads, pure inductive loads and capacitive ballast added to a resistive load to improve the performance of the tripler. The main information obtained is: (a) the relation between the triple-frequency output voltage and current with the input voltage and current at all values and for each type of load; (b) the phase of the output; (c) the iron losses. In addition, an important ferro-resonance phenomenon which occurs when the tripler is connected to a capacitive load is described. A method of deducing the relevant characteristics of the tripler starting from the magnetization curve is included mainly to throw light on the mechanism of tripling under differing load conditions. Reasonable agreement was obtained between experimental and predicted values.