## Power apparatus and electric machines

### More general concepts than this:

### More specific concepts than this:

- Sort by:
- Newest first
- Titles A to Z

### Filter by subject:

- Electrical and electronic engineering [33]
- Power systems and applications [33]
- Power apparatus and electric machines [33]
- a.c. machines [29]
- Synchronous machines [17]
- Instrumentation and special applications [5]
- Power networks and systems [4]
- Asynchronous machines [4]
- Measurement of specific variables [3]
- Electric and magnetic variables measurement [3]
- [3]
- http://iet.metastore.ingenta.com/content/subject/c,http://iet.metastore.ingenta.com/content/subject/c3000,http://iet.metastore.ingenta.com/content/subject/b3000,http://iet.metastore.ingenta.com/content/subject/b3100,http://iet.metastore.ingenta.com/content/subject/b3120,http://iet.metastore.ingenta.com/content/subject/b3120e,http://iet.metastore.ingenta.com/content/subject/b7310f,http://iet.metastore.ingenta.com/content/subject/b8150,http://iet.metastore.ingenta.com/content/subject/c3200,http://iet.metastore.ingenta.com/content/subject/b7200,http://iet.metastore.ingenta.com/content/subject/b7310g,http://iet.metastore.ingenta.com/content/subject/b7600,http://iet.metastore.ingenta.com/content/subject/b8110,http://iet.metastore.ingenta.com/content/subject/b8120,http://iet.metastore.ingenta.com/content/subject/c1000,http://iet.metastore.ingenta.com/content/subject/c1300,http://iet.metastore.ingenta.com/content/subject/c1320,http://iet.metastore.ingenta.com/content/subject/c3100,http://iet.metastore.ingenta.com/content/subject/c3110,http://iet.metastore.ingenta.com/content/subject/c3110b,http://iet.metastore.ingenta.com/content/subject/c3300,http://iet.metastore.ingenta.com/content/subject/c3340,http://iet.metastore.ingenta.com/content/subject/c3340h
- c,c3000,b3000,b3100,b3120,b3120e,b7310f,b8150,c3200,b7200,b7310g,b7600,b8110,b8120,c1000,c1300,c1320,c3100,c3110,c3110b,c3300,c3340,c3340h
- [3],[3],[2],[2],[2],[2],[2],[2],[2],[1],[1],[1],[1],[1],[1],[1],[1],[1],[1],[1],[1],[1],[1]
- /search/morefacet;jsessionid=4ca702pbp1aou.x-iet-live-01
- /content/searchconcept;jsessionid=4ca702pbp1aou.x-iet-live-01?option1=pub_concept&facetOptions=2+3&option2=author_facet&sortField=prism_publicationDate&pageSize=20&sortDescending=true&facetNames=author_facet+pub_concept_facet&value1=b8300&operator2=AND&value2=B.+Adkins&operator3=AND&option3=pub_concept_facet&value3=
- See more See less

### Filter by content type:

### Filter by publication date:

- 1949 [3]
- 1951 [3]
- 1970 [3]
- 1947 [2]
- 1950 [2]
- 1954 [2]
- 1956 [2]
- 1960 [2]
- 1962 [2]
- 1963 [2]
- 1966 [2]
- 1971 [2]
- 1959 [1]
- 1964 [1]
- 1968 [1]
- 1969 [1]
- 1972 [1]
- 1974 [1]
- See more See less

### Filter by author:

- B. Adkins [33]
- W.J. Gibbs [5]
- P. Bharali [3]
- R.G. Harley [3]
- S.S. Kalsi [3]
- A.R. Fagg [2]
- D.P.M. Cahill [2]
- Y.K. Ching [2]
- A. Hossle [1]
- B.W. Hogg [1]
- D. Williams [1]
- D.B. Mehta [1]
- D.D. Stephen [1]
- G.F.T. Widger [1]
- K.R. Dorairaj [1]
- L.J. Jacovides [1]
- M. Rama Murthi [1]
- M.K.E. Ismail [1]
- M.R. Krishnamurthy [1]
- N. Christofides [1]
- R.N. Sudan [1]
- Ronald G. Harley [1]
- S.C. Kapoor [1]
- S.K. Sen [1]
- V.N. Manohar [1]
- W. Philipp [1]
- Y. Takeda [1]
- See more See less

### Filter by access type:

The conventional theory of the synchronous machine is based on the assumption that the mutual inductances between the three direct-axis windings are all equal. The method is satisfactory for a calculation of the armature current, but the value of field current is considerably in error. Better results are obtained if another reactance is included in the equations to allow for additional coupling between the field and damper windings. The paper shows how the value of the additional reactance can be deduced from the short-circuit oscillograms.

A method is described of calculating the effect of large induction motors on the transient performance of a multimachine power system under fault conditions. The representation of an induction motor is similar to that used for synchronous machines, and is therefore suitable for describing composite systems. The method is based on Park's equations and, unlike earlier methods, allows for the ‘deep-bar effect’ usually present in large cage induction motors. The most accurate result is obtained by using the full set of equations, but more approximate methods using simplified equations are considered. The method is verified by tests on model machines connected by impedances representing transmission lines. Preliminary tests were made on a simple system comprising an induction motor connected to an infinite busbar through an impedance, and were followed by tests on a composite system containing a synchronous machine and an induction motor connected in parallel parts of the system. The results slow that good results are obtained with the accurate calculation which, however, requires a large amount of computer time, but that any approximation introduces considerable error.

To deal with a divided-winding rotor (d.w.r.) synchronous machine in which the two field windings are no^{t} located on the rotor axes and may not have equal numbers of turns, an equivalent machine is introduced with field windings on the direct and quadrature axes. The steady-state stability calculations are carried out by applying the Nyquist criterion to the linearised equations for small oscillations of a system with more than one feedback regulator. This investigation is followed by using the nonlinear differential equations and a digital computer to find the transient response after a change in the tieline impedance. The calculated results are confirmed by experiments carried out on the micromachine equipment at Imperial College, London. The alternatives studied included systems using one regulator at a time, both regulators together and various transfer functions for each regulator. The main conclusion is that the angle regulator stabilises the voltage regulator and has a major influence on the stability of the system; hence the voltage-regulator gain can be varied over a wide range.

The paper describes the development of a mathematical model which includes some of the phenomena commonly neglected in digital-computer studies. The model provides for the representation of damping more accurately than the simple method using a torque proportional to slip. For an even more accurate solution, it includes differential equations describing the variation of the flux linkages.Calculations are compared with test results of a large turboalternator incorporating a voltage regulator and governor, as well as with test results obtained from micromachine experiments at Imperial College, University of London, England. Calculated curves are included to show the detailed changes brought about by the more accurate equations.A comparative study is made of various methods and arrangements of numerical-integration techniques suitable for a digital computer. A table of comparative solution times is presented and the merits of the integration techniques are discussed.

Operation of a synchronous generator at leading power factor has been severely limited in the past because of stability considerations. A regulator, acting on a normal direct-axis field winding, can only extend the range of stability when the generator is loaded, and has no effect under unloaded conditions. An additional winding on the quadrature axis, provided with a suitable control, can, however, ensure stable operation at any leading-power-factor load, within the heating limit of the generator. The most effective control uses a closed loop actuated by a signal derived from the load angle. The theoretical treatment in the paper consists of two parts. First, some general results are deduced from simplified equations, particularly relating to the limitations of a direct-axis regulator and the benefit of using an angle signal with the quadrature regulator. More complete computations are then made to obtain stability-limit curves for many alternative schemes. The work is concerned with the steady-state stability of a l-machine system, in which a generator is connected to an infinite bus through a reactance. Experiments to confirm the theoretical results were carried out on the micromachine equipment at Imperial College. The alternatives studied included simple proportionate regulators and more elaborate schemes using first- and second derivative elements, and the angle signal was taken alternatively from the infinite bus and the generator terminals. Good agreement was obtained with the corresponding computations.

The asynchronous performance of a synchronous motor, at a given slip, may be estimated from the 2-axis operational-admittance frequency functions *Y _{d}*(

*js*ω

_{0}),

*Y*(

_{q}*js*ω

_{0}). The functions are commonly depicted as frequency-response loci. The frequency-response loci of a laminated-pole motor are shown to be analogous to the traditional induction-motor circle diagram. An accurate theoretical method is given to determine the asynchronous performance from the 2-axis loci, allowing for the effect of armature resistance. In addition, an approximate graphical method is given for the simplified condition when armature resistance is neglected.New equivalent circuits for the solid-pole motor are derived. The new circuits allow for the distribution of flux entering the rotor surface, and for the possibility of complete pole-tip saturation. Impedances, representing the parts of the magnetic circuit containing solid iron, are based on the rectangular magnetisation characteristic, and therefore have a magnitude, determined by the voltage across them, and a constant angle of 26.6°. The impedances are inserted into the equivalent circuits and the operational admittances are calculated by an iterative method. It is shown that the angle of the single effective ‘solid iron’ rotor impedance is found to lie between 26.6° and 45°, depending on the rotor frequency and flux. The method is also applicable to machines in which adjacent pole shoes are connected by end rings.Comparisons are shown between calculated and measured operational-admittance loci and between calculated and measured starting-performance characteristics for the solid-salient-pole micromachine at Imperial College, London, and for ten large solid-salient-pole machines of widely different dimensions and numbers of poles.A method of measuring, without attenuation, the component of oscillating starting torque of a synchronous motor, by measuring the total instantaneous input power, is demonstrated.

The load losses of an induction motor, defined as the difference between the actual losses and the conventional segregated losses under normal running conditions, have, in the past been difficult either to measure or to calculate accurately. An earlier paper gave methods of determining similar losses at larger slips and at reduced voltage, in terms of calculations and measurements of the torque/speed curve. The calculations allowed for saturation in the tooth tips, but not for saturation due to the full main flux which is present at normal voltage. The measurements were not made at full voltage because of heating considerations, and no useful measurements at normal full load were obtained because the load losses are a very small fraction of the input. In this paper, the method of calculation is modified, and improved testing methods are used to overcome these limitations, and thus to derive more reliable methods of measuring and calculating the load losses. Apparatus is described for the automatic recording of speed/torque and power-input curves at full voltage, from which the harmonic torques caused by the load losses can immediately be measured. The paper also describes a new back-to-back test for induction motors, which constitutes the most accurate and reliable method of measuring load losses under full-load conditions to date. Ten different rotors with carefully controlled parameters, used in conjunction with two identical stators, were tested in the back-to-back arrangement, and the results are compared with the theoretical computations and with the reverse-rotation test carried out on the same machines.

The paper records a detailed study of the effect of a voltage regulator on the stability of an alternator connected through a reactance to an infinite bus. The stability is analysed by means of Nyquist loci calculated for the transfer functions of alternator and regulator. The accuracy and speed of response of the system are also considered. The first part of the paper considers a simple regulator with proportional feedback, and it is shown that such an ideal regulator can extend the region of steady-state stability to a point corresponding to the maximum of the transient power-angle curve.Practical regulators are classified according to the nature of their transfer functions. The analysis provides a means of predicting their behaviour and explains how they affect the stability, accuracy and response. The effect of delay elements, integrator elements and derivative elements in the regulator is considered particularly; e.g. a buck-boost exciter, which effectively introduces an integrator element, gives good accuracy but less satisfactory response, and has a limited effect on stability, and a derivative regulator which gives rapid response and a large extension of the stability region, but has limited accuracy.Experiments performed on a model machine with various simulated regulators agreed well with the computed results. The computations allowed fully for the system parameters, including alternator resistance and alternator damping.

It has long been known that the performance of a turbogenerator differs in certain respects from that predicted by the idealised theory based on Park's equations. The reason is that the damping effects of eddy currents in the solid rotor are not correctly represented by damper coils acting on the two axes.The theory presented in the paper allows for the eddy currents in the determination of the direct- and quadrature-axis operational impedances *X _{d}*(

*p*) and

*X*(

_{q}*p*) They are calculated as frequency-response functions

*X*(

_{d}*j*ω) and

*X*(

_{q}*j*ω) by considering sinusoidally varying fluxes on one or the other axis in the machine at standstill. Two alternatives are considered: one when the flux reverses and the other when there are only flux changes of limited magnitude.The impedance values are used to calculate the characteristics during asynchronous operation and the current after a 3-phase short circuit. Two large machines and one model machine were tested and showed good agreement with the theory. A new method is suggested for determining the value of damping torque for use in a stability study.

A synchronous motor, constructed by modifying an induction motor by fitting a permanent magnet inside the squirrel-cage rotor, is very useful for drives where synchronous operation is required or where the drop in speed of an induction motor is too great. The paper presents a theory of operation of this type of motor and suggests an empirical design method. The analysis is based on the 2-axis theory of the salient-pole synchronous motor and shows how the properties of the permanent magnet can be taken into account.The principal difficulty in designing the motor arises from the demagnetizing effect on the magnet of the heavy currents which flow when the motor is started up and synchronized. The analysis consists of two parts. First, the performance characteristics are related to the direct-axis and quadrature-axis characteristics, which show separately the variation of flux and magnetomotive force on each axis. A method is then developed for calculating the axis characteristics from the *B/H* curve of the permanent magnet and the dimensions of the machine. In this way the performance can be predetermined.The method is verified by tests on an existing machine. Finally, two other designs, which could be expected to give improved performance, have been worked out.

The paper deals with the development of equipment for measuring the torque and load angle of an electrical machine under transient conditions and its use in verifying some theoretical results. The equipment is used in conjunction with a ‘micro-alternator’, which is a small machine specially designed to simulate a large generator.The torque meter uses resistance strain gauges mounted on a special coupling connected mechanically to the machine shaft. The load-angle meter operates by generating a succession of pulses which modulate the intensity of an oscillograph beam as it traverses a periodic wave.The experiments recorded relate to the following conditions:(*a*) Oscillations superimposed on steady operation as a synchronous machine.(*b*) Sudden short-circuit of an alternator.

The paper develops theoretical methods of calculating the variation of torque and load angle of a synchronous machine connected to a fixed supply voltage. In order to supplement and explain the results of recent full-scale tests the following conditions are considered:(a) Condition after a sudden short-circuit.(b) Condition after switching in a reactance between the generator and the supply.(c) Asynchronous operation.(d) Resynchronization after asynchronous operation.In a companion paper experimental equipment for measuring the variations of torque and load angle of a small synchronous machine is described. The equipment has been used to verify the theoretical results for each of the above conditions. The machine tested was a model alternator or ‘micro-alternator’ which simulates a typical large machine. The special laboratory equipment is of great value for studying in detail the factors governing the performance of large alternators.

The single-phase capacitor motor is an important type of electrical machine which requires lengthy design calculations to predetermine its performance. The paper describes a method of using a transformer analogue analyser to determine rapidly the currents and torque of the motor from its design constants, by direct reading on the analyser with very little auxiliary manual computation. The basic method assumes no saturation and gives the same results as are obtained by the slide-rule calculations in common use. With the analyser, however, the effect of changing any of the constants can be determined very quickly once the analyser is set up.In the second part of the paper, a method of allowing for saturation is described. Saturation is important because of the increase of voltage on the auxiliary winding caused by the capacitor under certain conditions. In order to develop a theory, the flux is resolved along two fixed axes and a different value of magnetizing reactance is used on each axis. When saturation occurs, the value of reactance for either axis varies not only with the flux in its own axis but also with the flux in the other axis. Theoretical and experimental methods of determing the appropriate reactances are discussed and the values are plotted on families of curves. With the aid of the analyser it is then possible to use a quick trial-and-error method to determine the performance of the capacitor motor with any degree of saturation.Test results on a capacitor motor are compared with calculations made both with the analyser and by manual computation.

The frequency-response method is well established in the analysis of control systems and networks, but has hitherto not been extensively used for analysing rotating machines. The method is of particular value When the magnetic circuit of the machine contains unlaminated iron in which eddy currents are set up when the flux changes. The paper describes a method of calculating the performance of the machine, and shows how the effect of the eddy currents can be taken into account.Several methods of calculating the appropriate frequency-response curves have been worked out and experimentally verified. The application of the frequency-response curves to determine the performance characteristics is illustrated by calculations and tests for several simple transient conditions.