MAGNETIC QUALITIES
Steel Sheets For
+
Transformers
.
COMPARISON OF DETAILS
Under the title "Specification Steel Sheets or Transformers for Power and Lighting' (B.S.I. Specification No. 601-1935) the British Standards institution has this year laid down clear- ly
Fritain certain for
prin- ciples
the to be adopted in sampling and testing of elecrical sheet steels. This Welcome specification may perhaps be regarded as the most recent im Similar specifications existence.
France and
exist in Germany. Americo.
The methods establish- ed for the measurement of iron losses and of permeability. how- ever, relate to subsequent opera- tion of the steels either under
ecnditions, steady" state direct-current work,
OF
in 08
under
purely alternating magnetisation. In no established specification is the case of magnetisation by combined alternating and direct Current (wn'ch has great com- mercial
importance included. The paper shows that this case uffers difruitles. In particular, correlation of alternating-and direct current test methods of measuring incremental permea- bility is not generally possible uwing to unsymmetrical wave- Form distortion introduced by Certain 08- even harmonies.
de- of this problem are pects uvnstrated and suggestions for methods of testing are put for wurd But the views of other sought. A experimenters are
discussion is already very desir- abile in the interests of present value of rescurch work. the
of which should be enhanced by agreement as to methods" of meas surement.
FLUX CONDITIONS The v.ew-point adopted in the paper is that the simple bal- listic method of measuring per- meability is only justified if the results are a guide to the be haviour of the Iron when excit- ed by alternating current, It is further assumed that the al- ternating flux conditions which are typical of most practical ap- plications of the iron should be speelfied" for the measurement of iron losses
....
A comparison of the details of the
to spec fieations various which reference has been made. shows that the peak nduction at which lossex are to be measured lies in the region 10.000 to 15 000 lines per square centimétre.
A
AERIAL SURVEY
WORK
Company's Great Project
5.ne wave u flux is to be eui- ployed and the cross section of samples, and hence the induction Is to be determined
from the standard dens.ty applying to the grade of sheet concerned. The use of ammeter, voltmeter. and and wattmeter is specided in all cases for the estimation of losses.
FULL RANGE
is
The point of most importance in the present discussion is that, except in Germany. the method of direct-current reversals specified for the measurement of permeablity." Attention should also be drawn to the range of inductions over, which this quality is to be determined.
Here there ไป considerly less agreement A full range to cover all spec!- fications might be stated appro ximately as B-2.000 to B=25 000, but the lower lim't'is only re- quired by the American Specl- figation. those of Britain. Ger- many and France starting much higher values.
at
For the present purpose the only comment which need be made upco the loss-testing clauses is that the adeption of sinusoidal induction is Justified by the fact that sheet steel wil operate approximately under the ARME cond tion in most practical alternating-current · ap- plications,
With regard to permeability, the justification for the direct- current method of testing seems to lle entirely in its simplicity to provide fundamental and ac- curate comparative data. Both are of great importance in the test laboratory.
HONG KONG DAILY PRESS, SATURDAY, OCTOBER 19, 1935.
ENGINEERING
TRANSFORMERS
How They Are Made
As the sta.10 transformer is one of the simplest of the op- paratus employed in connection with the generation und trans- mission of electrical energy, 1, is perhaps not surprising that its
main features have remained
much the same from the earliest years up to the present time. On the other hand, it has, especially since the war, undergone some notable changes in points of de- bail. One of the more important of these" has been an increase in size. In fact, it may be said that the output is now limited less by 'the electrical and mechanical. considerations, which were once predominant, than by the difficul- tles inherent in transporting the finished unit from the factory to the
working site. At the same time, cots and weigh have been reduced and higher cffelencs has been secured, whi e the adop.
of
tion of Improved methods manufac.ure have helped to- wards the a tainment of greater reliability and have simplified the details of production.
TWO TYPES
A firm which has played a lead- ing part in this development is 'he British Electric Transformer Company. Limited, Bush House, London. W.C.2. This concern was frs incorporated in 1898
to manufacture' the transformers covered by the patents of Mr. A. F. Berry, and the factory at Hayes. under the supervision of Mr. R. Weaving, as chief engin~ ter.
The range of manufacture pow covered is considerable gud Includ's power transformers with very varying capacities and of indoor and outdoor both the and
types, as well as for furnace and mining work, ··
The alternating-current bastic permeability measure- ments can, however, be correlat- ed and it is important to see
PRIMARY WINDING Hermetically-sealed patterns how this may be effected. In a
for employment in damp situa- series of magnetising current
tions are
also made, with, in waves for a range of sinusoidal
addition, instrumen. transfor- Induction amplitudes, the positive
mers and equipment for voltage and negative 'peaks of each wave
adjustment and. This
top-changing. ure of equal ampltude. characteristic Is due
the to absence of even harmonics, a well- of alter- understood property
which "nating-current excitation
be demonstrated readily
The ax's mathemat ca ly. zero current is, therefore.
and the
the time-meani piltude-mean of the distorted waves.
wou'd be if the as it waves were s'nustida'
Messrs. The de Havliland Com
Hatle.d Acro- pany, Limited. drome, Herts, have completed the construction of bree twin- engined aircraft which have been specially adapted for aerial survey work. These machines are the Dragon Rapide type, fitted with two 200-h.p. Gipsy 8ix ex nes, and have been ordered by the Netherlands New Guinea Pet- roleum Company. This company in ends to proceed with the sur. vering of some 25 milon acres ty aerial photography. In addi- tion to obtaining an in- dication of sites suitable. for petroleum production, the maps will furnish data regarding density of population in various districts and the best tracks" by which they can be reached, and information concerning forest and agricultural land. In addi ffon to a comprehensive standard equipment, the machines are St-- ted with bind-flying instruments, sun blinds, metal propellers, and Marconi transmitting and アビー celving wireless apparatus. À vertical camera, to take phon- graphs through the floor at RM ange of 148 deg., with uninter- rupted view. has been provided. The expedition will be fed by Mr. R. N. de Ruyter van Stevenick and it is anticipated that s com- mencement will be made on the Aurvy work at the end of Bep-- tember.
can
TELEVISION
Its Progress
of both
am-
Had the Government in Bri- tain encouraged television one- tenth as much 3.S the Ger- Government had done,
man
Great Britain would, have been well ahead of the rest of the world in television. and would have been firmly established a a leader of an important new industry. There were now about 130 workers in the Baird Labora tories, and they were still desir- cus of ob aming suitable men from the universities to assist in the research work required. Many problems remained to be solved by the prac ina. physicist with a good theore.ica. knowledge. al- ..though much money and the best brains available in the various coun ries had been employed wo bring television to its present state-Major 4. G. Church in Engineering.
!
J
SUSPENSION COMPASS
"A product of Messrs. Dobble, McInnes and Clyde Limited, pos- seasing special interest in view of ita ingenious design is the torque suspension compass,
In his compass the usual types of spiral or lent springs are re- placed by a ring subject to axial torsion, and means are provided for instantaneously varying the na ural period of his suspension If the binnacle is caused to vth- rate differenty" from the part!" cular reasonant frequency for which the suspension may have
り
Arm were responsible" for The some 2,000,000 KVA' of the "rans- formers now in use on the Bri- tish grid, and have recently coni- pleted a 20,000-kVA," 132/33-kV * spare on the unit for use as
men. Bame system. 1 may be tioned that there is still "a co- siderable demand for the origin. al Berry radial transformer, espc- cially where silent operation is essential. We may, therefore, re- call that the cores of these trans- formers are built up of a number uf L-shaped laminations, these being arranged so as to form a hollow cylinder from which arms project like the spokes of a whee! After insulation, this core is direc'ly wound with the first- half of the secondary winding. The primary winding, which is prepared in sections on wooden formers, is then slipped on and. finally,
an outer secondary is placed in position. The core la completed by bolting another ser.. des of L-shaped laminations over the whole.
been set initialy. Such changes in binnacle vibration may be due to variations in engine speed, ship loading, &, and unless they are countered, as in the present com- pass, there will be card oscilia- tion when a dry-card compass is used. The torque-suspension com. pass, though of the dry type is," therefore, equal in respect of freedom from card oscillation, to the liquid compass. The torque ring can be made out in the fi-. lustration at the top of the bin- nacle. The gimbal rings are suspended from it at two points, viz., one. forward and one aft, by short arms and inks, pivoted at the axis of the ring section. The pivots are formed as sleeves, which are carried in, roller bear- ings in brackets attached to the binnacle rim. At intervala round the circumference of the binnacle are other sleeves, he'd in brackets fitted with a clamping device! If ship Vibrations are applied to the binfacle, the bowl and, in conse- quence, the card, remain station- ary, the vibrations being absorbed by the twisting of the wire form- ing the ring, and not the twist. ing of the whole as referred to its rentre or the plane in which Its centre or the plane in which
AND
BUILDING
HYDRAULIC-POWER
Stream-Flow Date
as the basic month for power- In hydraulic-power engineering the computation of the "power rating purposes. The average Now available for development from of the lowest seven consecutive river-basing present a fundamen- days in that month is used in tal problem of very considerable determining the maximum avail-
able flow complexity, difficulties being en-
of the year, and the countered in the essentially pro-" average of all such maxima for the liminary work of assessing the years in which now statistics are
rate of discharge of the waterway, A river is fed by tributaries, and its rate of flow consequently varies from point to point. At any given point the discharge is subject to wide fluctuations, an extreme example being provided in tropical countries, where the Kow may be virtually or actually zero for a large part of the year, but may reach a remarkable magnitude for short periods during the monsoon...
STREAM-FLOW
In order to determine stream- flow data with any degree, of accuracy, observations over a long period of years are in fact neces- sary, and in the process of obtain. Ing them consideration, must be giver to the method of measure- ment most appropriate for the particular river. It will, however, often happen that the engineer is raced with the problem of rating river-basin for which gaugings are few or entirely lacking, and he must then use his judgmebt and experience in "estimating the diagnitude of the flow at different times. If it happens that the site under consideration comes within a catcament area of the
same general nature and size as one in which the relationship between run off and rainfall has been ex- perimentally determined, then, of course. the discharge" may be estimated with probably a high degree of accuracy.
The phenomenon of evaporation also has to be considered in rela- on to the percentage run-off: the magnitude of this factor varles widely from place to piace, anci its effect may become of impor tance not only in the run-of re- suiting from a given rainfall,out 4150 in its innuence upon storage reservoirs, especially where these are large in comparison with the catchment area. Again, the' quan- tity and character of vegetation in the district is known to in- muence the percentage run-off, if not also. Indesit, to some extent the rainfall itself.
FLOODS
countries
When the variety of in which the engineer is now called upon to plan water-power works is considered, in many of which no adequate records have veen taken, and often but the cost crude information regarding food phenomena la, avaliable, it wil be obvious that schemes must be planned with caution. A fur- ther aspect has also to be consi- Bereu for while the above are acme of the many compileating fuctors which bear upon
the stream-how available for power purposes, there are still further difficulties in applying the records when once they have been ob- tained or estimated. Not only is it necessary to deal with the statis- tics in such a way as to provide
ม่
avaliable is used as the effective maximum for the
purpose of calculations. Other countries have employed other methods, but it is evident that, "for statistica) uke for facilitating comparison ond between different sites throughout the world, some system of star- dardised treatment is desirable.
At the request of the World Power Conference, the International Electrotechnical Commission set up a committee in 1928 to make re- commendations for general accept- ance, and recently the British
pu-
Standards Institution have blished a specification in which the recommendations of the Inter- tional Electrotechnical Commission at a plenary meeting held in 1930 are now embodied..
In a foreword it is stated that "although the present methods of assessment d. water-power may vary, experts from a dozen coun- tries, having before them the full data of a stretch of river, and using the recommendations given In this specification, should be able to agree within narrow limits as to the "practical value" of the normal and maximum economic ratings."
A GREAT DISPLAY
The Shipping. Engineerlig and Exh.bi.ion opened Machinery recently
Olympia, At
IN COF- porates this year the Foundry Trades Exhibition and, in conse- quence, its scope is wider than in former years. In any case, it is a mistake to regard the Exhibi- tion as dominated by the first descriptive word or its tile, for, although a large number of the, displays are more or less directy concerned with shipping the en- gineer whose interests lls in other directions will find those inter- esis also catered for. This catho- city of aim is, indeed, reflected in the Use of Institutions, Asso- ciations and Societies, some 65 in number, that are paying official vista to
It the Exhibition. is further emphasised when the numcer of stands devoted to "enginearing materials and pro- cesses is considered, such displays Being applicable to the Industry genera ly. We stress this aspect of the Exhibition for the reason that, accompanying the growing lendency to segergation and spe- cialisation amongs engineers,
there seema an inclination to 25- sume that there is nothing to be learned from branches other than that with which the individual is concerned. At the same time. the shipowner, naval architect and marine engineer, will And that that part of the title of the Exhibition appealing to them does not belle 1's contents.
the information appropriate to the " It is true that ac.ual examples
scheme in hand; it is desirable also to obtain figures in form which will enable a true compari- son to be made with other schemes
and different sites.
The maximum power which can be developed "continuously" from a stream with no provision for artincial storage depends, clearly, apon the minimum flow, but at the same time it will be possible to Betteräte TL
very much greater amount of power than this for a part of the year. As to the maxi- mum economical development, and ine advisability of storage ponange, the merits of individual r CRECs must be the determining factors.
POWER-RATING
or
An invaluable instrument in the study of these matters is the dura- tion curve, in which are plotted as abscissae the percentages of time during which the flow is equal to or greater than the amount shown by corresponding ordinates. Some years ago the practice was sug- gested in Canada of arranging the months of the year according to the lowest daily flow, and the lowest of the six tigra
of motor boa.s' and so forth do noj now figure in the exhibits. these having been transferred, of late years, o a special section in the motor-car exhibtion, but marine machinery, both" for pre- pulsion and auxiliary purposes, la well Clustrated, and the exhibi- tion is particularly rich in dia- plays of instruments and appar- atus of the kind that are neces- sary for the effective running of a modern vessel. Experiment and investigation, too, are illustrated in an informative manner.
FOR A SIAMESE MINE »
Two types of Thornycroft vehl- cles were shipped a short while ago to the order of the Siamese Tin Mines Ltd., consisting of "Handy" class 2-ton and "Tartar" class 3-ton platform 'Jorries with tropical type cab. The bodywork incorporates stack sides to enable pipes and engineering plant to be carried safely un-country, while
WUL "Handy" class vehicle
4-wheel trailer.
AND
GEMENT
EMERALCRETE
RAPID HARDENING
PORTLAND GEMENT
IN PAPER BAGS OF 94LBS NETT
PRODUCT OF
GREEN ISLAND CEMENT CO. LTD.
EXCHANGE BUILDING, HONG KONG
THE TAIKOO DOCKYARD & ENGINEERING COMPANY OF HONGKONG, LIMITED.
·།། ་་?
BUILDERS OF ALL CLASSES OF SHIPS. BUILDERS OF RECIPROCATING STEAM ENGINES. BUILDERS OF MARINE AND LAND BOILERS: BUILDERS OF TURBINE MACHINERY
Under License From Messrs Parsons. BUILDERS OF DIESEL ENGINES
Under Special License
From Messrs. Sulzer Bros, Winterthur. Licensed To Manufacture Lanz Perlit Iron, Specially Suitable For Internal Combustion Engine Working Parts.
DOCK & SLIPWAYS.
FOR DOCKING VERY LARGE AS WELL AS SMALLER VESSELS,
ON ANY TIDE.
ALL CLASSES OF SHIP, ENGINE AND BOILER
REPAIRS AND EXTENSIVE
WELDING, BOTH ELECTRICAL AND OXY- ACETYLENE SKILFULLY AND PROMPTLY CARRIED OUT.
BUTTERFIELD & SWIRE, Agents,
* HONG KONG, CHINA & JAPAN..
TEL ADDRESS: "Taizconeck," Hoss Kong Talaruose: 80211.
CALL FLAG: "NUMERAL ONE" Over " PanNANT AND.'
HAS
WAR
STARTED IN
ABYSSINIA
PICTORIAL MAPS OF THIS
COUNTRY ARE OBTAINABLE
AT
HONGKONG DAILY PRESS
MOUNTED
50 cts, each
PRICES:
UNMOUNTED 25 cts each