The Electrician : the oldest weekly illustrated journal of electrical engineering, industry, science and finance, Vol. 139, No. 7 (3609)

FERRANTI, LTD., Halllnwood, Lancs. London Of f i ce : K ern H o u se , K in g s w a y ,W .C ,2

e r r a n t i

15 A U G U S T 1947 S I X P E N C E

F O R R E S T . . .

L i g h t i n g S p e c i a l i s t s

F o r e m o s t i n F l u o r e s c e n t The Fittings illustrated are available for I M M E D I A T E D E L I V E R Y

M A D E I N A C T O N , L O N D O N . G E O R G E

Orders are accepted, subject to our standard conditions of sale, a copy of which w ill be forwarded on request.

OSBORNE RD., ACTON, LONDON, W. 3.

E S T D . 1780

F O R R E S T

A N D S O N L T D

T e ’e p h o n e : A C O R N 5081 (5 lines) T e le g ra m s : G E F S O L , È A L Ü X , L O N D O N An open-ended trough pendant fitting suit­

able for most industrial uses. Finished stove enamelled white internally and cream exter­

nally. Fitting can be supplied to carry 1, 2 or 3 Lamps. A lso available with Vitreous Enamelled Reflector.

G 2760

An industrial ceiling fitting with built-in control gear arranged for easy access.

Lampholder covers instantly detachable.

Finished white stoved enamel. Fitting can be supplied to carry I, 2 or 3 Lamps.

Enquiries are invited for speoiai- purpose fittings for either tungsten or fluorescent lamps for which an expert designing staff is available.

THE ELECTRICIAN IS AUGUST 1947

.hl« C K - «

h~ j l c.s-.i t*«tNo 'c* !>•■ «">»"*j*’

[ -'""“Xh.-ro.

J5

AUGUST 1947 THE ELECTRICIAN

T R A P I N E X P a i n t T R A N S F E R S

T h e F i n i s h i n g T o u c h ! L IN K YOUR PRO DUCT AND P U B L IC IT Y B Y B R IL L IA N T T R A P IN E X P A IN T T R A N S F E R S

The method of marking a product by means of brilliantly coloured paint printed

“ Trapinex” transfers affords the perfect link up with other forms of publicity at point of sale. L. G. Hawkins & Co. Ltd. use this method of tying the nameplate in their press advertising with the same design of

“ Trapinex” transfer on their electrical products.

“ Trapinex” (Regd.) Transfers offer all the advantages of paint over printer’s ink.

More brilliant colours in any number, bold design, long lasting durability, washability, and weather proof qualities.

W I N D O W P U B L I C I T Y

F o r w in d o w d is p la y a p p lie d d ir e c t to the g la ss in open designs, “ T r a p in e x ” P a in t P r in te d T ra n s fe r s have u n iq u e a d v a n ta g e s— no film o r p a p e r b a c k g ro u n d o b sc u re s the go ods, a p o in t w h ic h r e ta ile rs fu lly

a p p reciate .

Y o u r M a r k in g P roblem s Solved!

“ Trapinex” Paint Transfers (Patd.) are used for an immense variety of purposes on products as diverse as cosmetics and heavy machinery for brand marks, name plates, warnings, diagrams, decorations, etc., as well as for packaging, display and publicity.

Direct printing in paint on gleaming plastics by the “ Trapinex” process provides display cards for window or counter display at point of sale, or for railway and tube sights.

A d v ic e fre e ly give n , b u t w h e n y o u w rite fo r p ric e s please state :— (

1

2

3

4

5

6

T R A P I N E X

(

.)

. TRAPINEX LTD., 19, Commerce Works, 43, Commerce Road, Wood Green, London,

’P h o n e : B o tc e s P a r k

68

438

THE ELECTRICIAN

AUGUST 1947

o u t p u t

s t e p p e d

u p

In the last six months we doubled production of 212K Memroy all-insulated switch-fuses. We showed substantial output increases in other M.E.M lines too, and the production drive continues. Before very long, the sheer weight of M.E.M. output will certainly make itself felt. But industry and housing are still demanding tremendous quantities of M.E.M. gear and, in spite of this fine response from the factory, demand still keeps ahead of supply.

Your wholesaler has the difficult job of sharing out such supplies as are available. Your best plan is still to keep in touch with him.

Midland Electric Manufacturing Co. Ltd., Birmingham, 11 • Branches in London & Manchester

9 ' ïHg; BR

TISH ^

rHOMS0N'HOUSTG|f Ca t i m e r rrre kb fchm ■ w p i^.

ft b r i t i s i p a t c n ts ó m*

W r i t e f o r list N o . 5 6 4 2 - 5

T H E B R IT IS H T H O M S O N -H O U S T O N C O M P A N Y L IM IT E D . R U C B Y . E N G L A N D

m

A 37 61

I N D U S T R I A L

E L E C T R I C

T I M E R

Designed to with­

stand frequent and ar­

duous service in indus­

try, the BTH Timer has three ranges, namely:—

u p t o 5 m i n . in S se c . s t e p s, u p t o 2 0 m in . i n 2 0 se c. s t e p s , u p t o 6 0 m i n . i n 6 0 se c. st e p s.

It is controlled by any form of pilot switch or push button and will give lasting trouble-free service.

i S AUGUST 1947 THE ELECTRICIAN

440 441

N o . 2 T O O L A N D C U T T E R G R I N D E R T h is m a c h in e re q u ire s n o introd u c tio n . Its u n u su a l fle x ib ility p e rm its a va rie ty o f m illin g c utte rs, re a m e rs, f o rm tools, h ob s, etc., to b e easily, q u ic k ly and a cc ura te ly g ro u n d .

W h e r e the se m a c h in e s a re installed, re d u c tio n s in s h a r p e n in g tim e o f 15/- to 2 5 * / a re re g u la rly e ffe c te d — a valuable c o n sid e ra tio n w h e n p la n n in g inc rea se d p ro d u c tio n .

v e r s e v e r y a s p e c t o f

W O N Q SE T TO O L A N D C U T T ER G R IN O E R Be c au se o f th e M o n o s e t ’s e x tre m e fle x ib ility a n d b u ilt-in fe ature s, all o p e r a t io n s re q u ire d to p ro d u c e c utte rs can b e c o m p le te d in o n e setting.

T h e S p ir a l L e a d M e c h a n is m g e n e ra te s st r a ig h t o r tap ere d , rig h t-h a n d o r left- hand, in fin ite ly v a ria b le sp ira ls w ith a sin gle sim p le a djustm ent.

E x c e lle n t c on ce n tric ity is a ssu re d w ith su b se q u e n t s m o o th c u ttin g a ctio n a nd lo n g to o l life.

C O N T O U R C U T T E R G R I N D E R | In t r o d u c in g fo r the first tim e the a d v a n ta g e s o f c o n t o u r g r o u n d 'm il lin g c u tte rs fu lly c o m p e n s a te d f o r e ith e r u n d e r c u t o r h e l ic a l t e e t h o r , if re q u ire d« b o th to g e th e r. .

M a s t e r te m p la te p r o v id e s re q u ire d form .

M a c h in e c o p ie s f o rm w ith a n y d e sire d c le a ra n c e angle.

A s im p le a n g u la r se ttin g c o m p e n s a te s fo r “ u n d e rc u t " .

In te rc h a n g e a b le “ h e l i x " c a m s m o u n t o n th e left e nd o f t h e w o r k sp in d le a nd c o m p e n sa te f o r h e lix angle.

T h e re s u lt — a n e w s t a n d a rd o f f o rm m illing.

A l s o g r i n d s : — C ir c u l a r F o r m T o o ls.

S in g le P o in t F o r m T o o ls.

THE ELECTRICIAN IS AUGUST i 947 IS AUGUST 1947 THE ELECTRICIAN

THE ELECTRICIAN IS AUGUST 1947

443

The estimated number of electric cookers in service indicates YO U R potential market for S IM M E R S TA T S !

The SIM M ER S TA T (retail 21/-), fitted in place of the usual 3-heat or 4-heat hot-plate switch, M O D ERN ISES any cooker, providing PER FEC T S IM M E R IN G control.

Every housewife that cooks by electricity is a potential customer. W rite now for Trade Terms for immediate delivery to :

S U N V I C C O N T R O L S L T D .

STANHOPE HOUSE, KEAN ST., LONDON, W.C.2

C U t 'k e a t

HOTPLATE

CONTROL

IS AUGUST 1947

TAS/SC. 119

THE ELETRCICIAN

f t . H j Y M O N D i

E2I47

15 a u g u s t 1947

O p e n m a r i n e - t y p e s w i t c h b o a r d c o n t r o l l i n g t h r e e 2 0 0 k W g e n e r a t o r a a n d c i r c u i t s a n d I n c o r p o r a t i n g D o r m a n X L a l r - b r e a k c i r c u i t b r e a k e r s a n d D o r m a n " F " t y p e s w i t c h e s a s i n s t a l l e d o n t h e L . N . E . R a i l w a y 's n e w c a r g o l i n e r S . S .

( J o h n B r o w n & C o . ,

in o n e o p e r a t io n o n a ll- B r i t is h h ig h sp e e d m a ­ c h in e s u s i n g T u n g s t e n C a r b id e a nd D i a m o n d d ie s, g i v in g p e rfe c t fin is h a nd g a u g e t o m e e t th e m o s t e x a c tin g sp e c ific a t io n s r e ­ q u ir e d to-d a y .

47, Victoria Street,

W e s t m i n s t e r » L o n d o n , S . W . I T e le p h o n e : A b b e y 27 71 (Pte . B r. E x .)

W o r k s ; E n fie ld , M id d le s e x

IS AUGUST 1947 THE ELECTRICIAN

. . . n e w in design, efficiency, simplicity and scope.

This example from the range of ne w protective relays developed by C H A M B E R L A I N & H O O K H A M LTD., is an overcurrent and earth leakage relay which combines most advantages of earlier types of protective devices with a number of especially valuable features.

LOW CONSUMPTION HIGH SENSI TI VI TY

HIGH TORQUE READY ACCESSIBILITY

EAS Y READI NG

For full information apply to the Manufacturers :

C H A M B E R L A I N & H O O K H A M LTD. B I R M I N G H A M

n

P R E S S T O O L S P R E S S I N G S M O U L D S A N D J I G S

S E E W H A T I S S T O P P I N G F A S T R

W I T H 0 U T M A C H I N E S

By installing a S c o p h o n y E le c tro n ic S tr o b o s c o p e detailed inspection of all moving parts can be made without slowing o rstop pin g machines ; or interfering with production in any way. The Stroboscope is a highly sensitive instrument which arrests visual motion, thus allowing the effect of vibration, bounce and wear to be observed in all rotating and reciprocating mechanisms.

Such inspection saves sudden breakdowns and gives a truer appreciation of

"ca u se and effect” in all types of machinery.

The S c o p h o n y S tr o b o s c o p e is the wonder of this mechanical age and no wise maintenance engineer can afford to be without one. It is indispensable in mills, factories, garages, research laboratories, locomotion and a host of other places,

— it’s

another

S C O P H O N Y L I M I T E D

THE ELECTRICIAN iS AUGUST 1947

447

C R O M P T O N P A R K I N S O N L T D , A S T O R H O U S E ,

Telephone : C H A n c e ry 3 3 3 3

C H , L O N D O N , W .C .2

Telegra m s : C ro m p a rk , E stran d , London

j 5 AUGUST 1947 THE ELECTRICIAN

enow«*

m ufacturers

ge and small

cmpl°>’ * * ' 0 raise the

oH in trans- ,ear » oVCt

„„ -puiiy

,assage- and automatic

* 800 gallon

V o N D O H

THE ELECTRICIAN IS AUGUST 1947

P R I S M A L U X

D I R E C T I O N A L L I G H T I N G U N I T S

This new Die-cast Prismatic Fitting replaces the old style bulkhead fitting.

For horizontal or vertical mounting.

Writer or

580

1

I N E E R I N G C O M P A N Y L T D .

C H E S T E R 16.

Tel. TRAfford Park 1801

Lines)

London Office :

34

VICTORIA ST., LONDON, S.W. I

Atlas lamps brighten up even the most brilliant ideas-men . . . throw new light on obscure situations . . . stay steady and strong when the human element fails. More and more efficient people are specifying Atlas lamps because they have checked up that for long life and sheer light value there is no better lamp.

Every Atlas lamp is guaranteed to be made to strict B.S.I. specifica­

tion and is tested at each stage of manufacture. Write for terms today.

A C O M PLETE L IG H T IN G SERVICE O u r lighting engineers will supply

you w ith exactly the lighting you need, exactly w here you need it. We design and supply m odern fittings using new m aterials boldly, yet

planned w ith comm on sense and

‘ eye-appeal ’. W e offer you a com ­ plete, individual lighting service.

W hy not get in to u c h ? There is no obligation.

A T L A S L A M P S

f o r S T A Y I N G P O W E R

aI36 T H O R N E L E C T R I C A L I N D U S T R I E S L T D . , I0 5 - I0 9 J U D D ST., LONDO N, W .C .I T e l.E u sto n 1183

N O R T H E R N B R A N C H : S T E V E N S O N S Q U A R E , M A N C H E S T E R L T E L . C E N T R A L 3185 N .E . D E P O T : 4 6 S A N D H IL L , N E W C A S T L E -O N -T Y N E 1. T E L . N E W C A S T L E 24068

N E X T T I M E H E L L G E T A H A T L A S

IS A U G U ST 1947 THE ELECTRICIAN

TELEPHONES Lt*.

2 2 , L I N C O L N ’ S I N N F I E L D S W . C . 2

THE MODERN TREND

BR1T1SH L I MI T E D

U M L X

METRUM W O R K S, BEATTY ST., CAMDEN T O W N , L O N D O N , N .W .l . EUS. 5951-2-3 trical equipm ent is a vital factor in the

competitive m arket o f today. N o dealer can afford to display or attempt to sell, an appliance which is not completely up- to-date in design and wholly reliable in performance . . . . as, in turn, no house- svife can resist the clean modern lines and labour-saving efficiency o f DIAM IX products.

T H E A U T O M A T I C T O A S T E R

is but one example from the D IA M IX range, which also includes the

“ Junior ” and “ Push button ” Cookers, Thermostatic Irons, Fires and Boiling Rings. Please write o r 'phone for New Season's Catalogues.

THE ELECTRICIAN IS A U G U ST 1947

(t C am e a t m e lik e a c a m io n b all — th e id e a t h a t it c a n be m a d e i n ru b b e r . M u s t s p e a k to L o riv a l a b o u t i t ! ”

R U B B E R O R P L A S T IC S ?

While each material possesses its own characteristics, in m any applications one is as suitable as the other, and in these times o f scarcity it is as well to have this in m ind. Firm s in need o f components, complete articles or packaging should seek our advice, which is based upon wide experience and specialized knowledge. We produce articles in rubber and ebonite as well as plastics, and our service includes design and manufacture.

L O R I V A L P L A S T I C S

j f U Y U N I T E D E B O N I T E & L O R I V A L L I M I T E D E O L ) L I T T L E L E V E R , N E A R B O L T O N , L A N C S

A U G U ST 1947 THE E L b C iK iC lA N

E L E C T R I C A L A N D R A D I O E N G I N E E R S

q u ic k ly a p p r e c i a te t h e v a lu e o f h a v in g a re e l o f B a r le c ta A d h e s iv e T h r e a d h a n d y i n t h e i r t o o l k i t o r o n th e

b e n c h in t h e w o r k s h o p .

C O M P L E T E O V E R H A U L S R E W I N D I N G

A N D

Q U I C K D E L I V E R Y

$i>l)csiuc \

ÍBarlecta)

■ ïbreaù

p e r 100 ya rd

REEL

(subject)

W o u n d o n metal s p o o l . E n c l o s e d I n

a l u m i n i u m

case.

Please o r d e r th ro u g h y o u r usual W holesaler.

B A R R I E S

ELECTRICAL AGENCIES LTD.

K IN G S T R E E T , B R IG H T O N , 1 .

Telephone: Brighton 8366 (7 lines) P .B .X .

ELECTRICAL CO. LTD.

412-414, C A L E D O N I A N R O A D . I S L I N G T O N , L O N D O N , N.7.

Telephone : NORTH 4871-2

The ra th e r rummy looking object above is one section of the new DS skirt for surface mounting the DS conduit box type socket. The other section is an absolute tw in, a n d th ey g e t to- g e th e r as show n below.

This e n a b le s the skirt to be fixed after the w iring h a s b e e n com pleted an d m eans g re a te r ease for the w irem an.

Tust another in g en io u s addition to the DS F used

Plug and Socket ra n g e .

A n n o u n cem en t o f V S P lu g , L td ., M a n c h e ste r . London . G lasgow T H E E L E C T R I C I A N

EIM-47 I S A U G U S T

453

T h e J o b was to sweat on the fins using a minimum of solder and man hours and w ithout employing skilled labour.

T h e M e t h o d was by using Fryolux Solder Paint.

This was trickled on to the tubes between the fins. The whole unit was then placed in an oven and heated and the job was done. For quantity production a special container was made having the requisite number of spaced holes from which Fryolux Solder Paint flowed on to the tubes between the fins.

F R Y O L U X S o l d e r P a i n t

FO R TINNING AND SW EA T SO LDERIN G

A p p ly by b ru s h in g , sp ra y in g o r d ip p in g — h e a t by a n y c o n v e n ie n t m e a n s— an d t h e j o b ’s d o n e .

7 0 % S A V I N G I N M A T E R I A L

5 0 % S A V I N G I N L A B O U R C O S T S FRY'S METAL FOUNDRIES Ltd., Tandem Works, Merton Abbey, London,S.W

.1 9

A n d at M A N C H E S T E R , G L A S G O W , B R I S T O L a n d D U B L I N .

T h e a r t i c l e w a s a C o p p e r H e a t E x c h a n g e r

15 A U G U ST 1947 THE ELECTRICIAN

W

HASLAM ST., CASTLE BOULEVARD, NO TT IN G H A M

k

'P H O N E : N O T T I N G H A M 4 6 0 6 8 <3 U n c i )

‘G R A M S : C A P S T A N . N O T T IN G H A M

ON AIR MINISTRY. ADMIRALTY AND WAR OFFICE LISTS

R E P E T I T I O N W O R K

I N A L L M E T A L S Plug with Guard Ring to

protect Pins

Terminal Socket & Cover

W E A T H E R P R O O F M E T A L - C L A D

PLUGS & SOCKETS

5 to 300 Amp. 250 / 500 Vo!?..

3 and 4 Pole Earthed Type and 2 Pole.

For E le ctric L ig h tin g and P ow er, Tra nsm ission, C o m m u n ic a tio n , P o r ta b le Tools, etc.

Cast Brass Terminal Socket and Cover

Through Socket and Cover

M a n u f a c t u r e d b y

S IM M O N D S & S T O K E S L T D .

V IC T O R I A H O U S E . S O U T H A M P T O N R O W .' L O N D O N . W .C .I ; H O L B O R N M )7

THE ELECTRICIAN 15 A U G U ST 1947

A d vt. of Pirelli-General Cable Works L td ., Southampton.

15 A U G U S T 1947 THE E L E C T R IC IA N

OIL-FILLED SUPER TENSION

3 3 k V t o 3 3 0 k V

I ^{i r e l u} - ^l I ^{en er a} I

M A N U FA C T U R E R S OF EVERY K IND OF ELECTRIC CABLE

M O U L D I N G P R E S S E S

T h e new EM B W P L A S T IC M O U L D I N G P R E S S E S em body m any up - to - date features :

Heavy w elded steel side fram es, replacing th e old ro u n d type pillars, give great rigidity and enable th e moving platen to be provided w ith proper slides.

T h e bearing surfaces lie radial­

ly from the centre of the platen so th at any expansion due to variations in tem perature has no effect on the w orking clearance.

M ade in up-stroke and down- stroke types. 25 to 160 tons.

E

■ l l l i D i LTD. B R O M W IC H

J u s i n g fa c ilitie s

I E N G L I S H 1 E L E C T R I C

I N D I C A T I N G

•y E N G L I S H E L E C T R I C 44 R ” T Y P E

"3 S I E M E N ’S J 500 v. D . C . T R A C T I O N A S L Y D L O K

R E W I R A B L E F U S E L I N K

E .M .B .W . 160 TON M O ULD ING P R E S S .

F ^{m b} W

S I M P L I F I E D

A D A P T A B I L I T Y

S h a rs to n Road, W y th e n s h a w e , M a n ch e ste r.

EDWARD

The fuse you will eventually use

T h e la rg e r sizes in th e N e w S L Y D L O K Fuse range p ro v id e fo u r a lte rn ative d e g re e s of p ro te c tio n , fro m 2 5 0 A C D C 3 , u sin g th e stand ard S L Y D L O K re w ira b le F u se lin k (at the co st of a fuse w ire ,) t o S O O A C D C 4 , u sin g o n e of t h re e p ro p r ie ta r y m akes of H .R .C . ca rtrid ges, as sk e tch e d above, all w it h o u t change o f h old er.

Lo w e r, but n o t higher, rated ca rtrid g e s m ay be In se rte d in each respective size fu se h o ld e r and, equally im p o rta n t, n e ith e r can be inse rte d o r used in th e base w it h o u t the o th e r.

THE ELECTRICIAN

dm E.W . 13

IS A U G U ST 1947

E L E C T R I C W A T E R - H E A T I N G

S934A Trade Mark "SANTON”

I T AU G U ST 1947 THE ELECTRICIAN

D a ta -b o o k in th e in d u s tr y . . .

No more v alu ab le time w asted h u n tin g up the rig h t w ater h e a le r to suit Mrs. Smith ! All the inform ation you require is a t your fin g ertip s in the new Santon D ata-book. C ontents of this h an d y re fe re n c e volum e in clu d e : SPECIFICATIONS o f a l l SANTON

e l e c t r i c h e a t e r s a s w e l l a s d e t a i ls o f l o a d i n g s a n d s iz e s .

WORKING DRAWINGS to h e l p m a k e i n s t a l l a t i o n e v e n m o r e s im p le .

FLANGES f o r e v e r y t y p e o i i m m e r ­ s i o n h e a t e r f u l l y d e s c r i b e d . A Ibo d e t a i l s o f s p e c i a l f i x i n g t o o ls .

WATER HEATING FORMULAE.

Useful inform ation in clu d es tem . p e ra tu re conversion c h a rt a n d formulae to provide a ll re le v a n t information.

AUTOMATIC CALCULATOR. A t - a - g l a n c e f i g u r e s g i v e c a p a c i t i e s of

c iB t e r n s a n d c y l i n d e r s of a l l s i z e s .

W rite for your Copy of the Santon D ata Book now to SANTON LTD A NEWPORT. 15, MON. (Tel. : 71211-3).

1 . T h e m o s t c o m p le t e a n d c o n v e n ie n t

Why it pays to s p e c if y “ SANTON” :—

457

1 5 , 0 0 0 N T F E ^BATTERIES

o n d u t y 1 0 y e a r s

f o r r e p a i r s !

This was the actual experience of a Railway Company operating N IF E Batteries under very severe conditions. Obviously N IF E is no ordinary battery. It is an Alkaline cell of all-steel con­

struction, practically indestructible, entirely free from corrosive fumes and immune from damage even by dead “ shorting.”

? r o o f t h a t t h e r e i s

more Lift , N IF E

Nozu available fo r all purposes except private radio and private cars.

N IFE BATTERIES LT D ., R ed d itch , W o r c i.

THE ELEC TRICIAN IS A U G U ST 1947

Bouverie House

Fleet Street

London E C

Number

Vol

No.

C O N T E N T S

V iew s on Current A ffairs ... 459 A b o u t T ransform ers— I ... 462 E a rth in g P roblem s ... 467 Stan d a rd isa tio n o f Voltage ... 468 P ortrait— S ir George N elson ... 469 E lectrical Personalities... 470 L o a d Spreading ... 471 B o o k R eview s ... 472 L o co m o tive T estin g P lant ... 473 N o te s fro m In d ia ... 474 E lectricity S u p p ly ... 475 E lectrical S ta tistic s ... 476 R iversid e S ta tio n a t Poplar ... 477 E q u ip m e n t a n d A p p lia n c e s ... 478 In d u stria l In fo rm a tio n ... 479 C ontracts O pen ... 481 C om pany N ew s ... 482 Commercial In fo rm a tio n ... 484

M I D L A N D S O F F I C E :

D a i m l e r H o u s e , P a r a d i s e S t r e e t , B ir m i n g h a m T e l e p h o n e : M i d l a n d s 0 7 8 4 — 5

S C O T T I S H O F F I C E : 1 1 6 , H o p e S t r e e t , G l a s g o w , C .2 T e l e p h o n e : C e n t r a l 3 9 7 0

The offices o f T h e E l e c t r i c i a n are closed on S a tu r d a y s in accordance with the n F ive-day W e e k " p la n adopted by B enn Brothers, L td .

S I N G L E C O P Y (FRIDAY) - - - 6 d .

(B Y POST) - - 8 d .

A N N U A L S U B S C R I P T I O N

H O M E A N D O V E R S E A S - 3 0 s

C r i s i s a n d E x p o r t s R

th o e le c tric a l in d u s tr y , t h e a r r a n g e ­ m e n ts d ra w n u p to m e e t th o n a tio n a l c risis sh o w a la c k of u n d e r s ta n d in g of th o g e n e ra l in d u s tr i a l p o sitio n , of th o c o n d itio n s n o w o b ta in in g , a n d of th e r e q u ir e m e n ts fo r im p ro v e m e n t.

H ig h in th o li s t o f o b je c tiv e s to be a tt a in o d is a n e x p a n s io n o f e x p o r t tr a d e , a n d sin c e th o e le c tric a l i n d u s tr y is a lr e a d y c o n tr ib u tin g s u b s ta n tia lly to t h a t t r a d e w h ile m e e tin g th e d e m a n d s fo r g e n e ra tin g a n d o th e r e q u ip m e n t a t h o m e, i t is in a p o s itio n to lo o k u p o n th o e x ­ p o r t . fo r e c a s ts m a d e b y G o v e rn m e n t s p o k e s m e n w ith a n a p p r e c ia tio n o f th e difficulties, s o u n d e r in i t s ju d g m e n t t h a n t h a t of th e p o litic a l w o rld .

A n y rcv io w o f th o s e fo r e c a s ts m u s t, in th o f ir s t place, ta k e in to a c c o u n t th o f a c t t h a t m o s t o f th e in d u s tr y o f th o c o u n tr y a s a w hole— fr o m th o m a k in g o f m a c h in e s to th e p r o d u c tio n of c o tto n g o o d s; fro m t h e m a k in g o f s te e l to th e m a n u f a c tu r e o f f u r n i t u r e ; fro m th e b u ild in g o f s h ip s to th o ru n n in g of ra ilw a y s — is la r g e ly d e p e n d e n t in v a r y ­ in g d e g re e o n t h e re n e w a l o r f i r s t in s t a l ­ la tio n o f e le c tric a l p l a n t of v a r io u s k i n d s ; o n o le c tric a l p o w e r to r u n t h e p l a n t s ; a n d in m a n y c a se s o n c o n tin u o u s elec­

tr ic i ty s u p p ly fo r p ro c e s s o p e ra tio n . F o r w ell o v e r tw o y e a r s th e n a ti o n a l p e a k lo a d h a s b e e n a t a fig u re f a r in ex cess of g e n e ra tin g c a p a c i ty ; t h e m a n u f a c tu r ­ in g o u t p u t o f e le c tric a l p l a n t fo r in d u s ­ t r y h a s b e e n r e s tr ic te d b y s te e l a n d o th e r s h o r ta g e s ; lo a d s h e d d in g h a s b e e n w id e ­ s p r e a d in th e v a n te r m o n t h s ; a n d th e p o w e r s t a ti o n s h a v e b e e n s h o r t o f coal.

T o m e e t th e s e c o n d itio n s th e in d u s tr y of th e c o u n tr y is n o w en g a g e d in s h a p in g sch em es w h ich w ill b y s ta g g e rin g w o rk ­ in g h o u r s re d u c e th e p e a k lo a d b y a t h i r d ; b y rig id e c o n o m y in p o w er co n ­ s u m p tio n in th o d o m e s tic h o ld d u rin g th e s u m m e r, c o a l s to c k s h a v e b e e n b u ilt u p a t th e ¡low er s ta ti o n s to a v o lu m e e q u a l to fo u r a n d a h a lf w e e k s’ w in te r s u p p ly ; a n d sin c e J u l y l a s t y e a r a n in ­ c re a s e in g e n e ra tin g c a p a c ity o f a b o u t 330 M W h a s b e e n b r o u g h t a b o u t. So f a r so g o o d ; b u t a g a in s t th o l a t t e r fig u re o f 330 M W a d d itio n a l p la n t, m u s t be re c o r d e d th e f a c t t h a t th e n a tio n a l d e m a n d fo r e le c tric ity s u p p ly d u rin g J a n u a r y to J u n e t h i s y e a r in c re a s e d b y a b o u t 5.8 p e r c e n t, w h e n c o m p a re d w ith th e firs t h a lf o f 1946, a n d la s t w eek -en d s t r e e t a n d f a c t o r y lig h tin g w e re a d d e d to th e l o a d . ,

S ales a n d P r o d u c t i o n

T H E a b o v e e x a m p le s o f th e c o n d itio n s u n d e r w h ich th o in d u s tr y of t h e c o u n tr y is w o rk in g a r e o n ly a few o f th o s e w h ic h c o u ld b e q u o te d , b u t a re , w e s u b m it, su fficien t in n u m b e r to in d ic a te t h a t th e e x p o r t ta r g e ts h e ld u p b y th e G o v e rn ­ m e n t a r e la rg e ly th e o r e tic a l in v a lu e in th o p r e s e n t s ta g e of p o s t-w a r reco v ery , a n d in a n y c a s e m a k e no a llo w a n c e fo r th o f a c t t h a t c o u n trie s, u n h a m p e r e d b y a n y fo r m o f crisis, a r e c o m p e tin g fo r th e s a m e o v e rs e a s tr a d e . T h a t in d u s tr y in g e n e ra l w ill do it s b e s t a n d t h a t th e elec­

tr ic a l in d u s tr y in p a r t ic u l a r w ill do e v e ry th in g p o ssib le to m e e t th e d e m a n d s m a d o u p o n it, a r e n o t in d o u b t ; it. w ould, h o w ev er, b e w ro n g fo r th e p u b lic to b e le d in to b e h o v in g t h a t th e u n q u a lifie d m a n u f a c tu r e o f g o o d s fo r e x p o r t is th e sole so lu tio n . A p a r t fro m th e n e c e s s ity of p u tt in g o u r ow n h o u se in o rd e r b efo re w e c a n h o p e to p ro d u c e a t m a x im u m c a p a c ity , th e g o o d s w h ic h w ill r e s u lt w h en t h a t c o n d itio n o b ta in s w ill h a v e to b o s o ld in a m a r k e t a lr e a d y sh o w in g sig n s of b e c o m in g se le c tiv e c o m p a re d w ith a y e a r ago. I n th e s e c irc u m sta n c e s, in q u ir y m u s t bo m a d e to e n s u re t h a t th e g o o d s w e m a k e w ill b e th o s e w h ic h w ill bo w a n te d a s th e m o n th s go b y ; a n d t h a t th e y a r e o ffered a t th e right, p rice.

Less I n t e r f e r e n c e —M o r e M a te r ia l s G O V E R N M E N T sp o k e s m e n s u g g e s t t h a t p r o d u c tio n is th e k e y to th o c risis p r o b ­ lem s, a n d th o u g h p ro d u c tio n , b r o a d ly

a n d sim p ly , m ig h t h a v e b r o u g h t th e d e sire d r e s u lts a y e a r ago, to -d a y , o u t ­ p u t m u s t b e b a la n c e d a g a in s t q u a lity in d esig n , p e rfe c tio n in p e rf o rm a n c e a n d a d v a n c e d te c h n iq u e . T h e s e c o n d itio n s a re , i t is c e rta in , w ell w ith in th e c a p a c ity of B r itis h in d u s tr y , b u t if th e y a r e to b e m e t, w ill d e m a n d , fro m G o v e rn m e n t d e p a r tm e n ts , less in te rfe re n c e a n d th e m a x im u m p o ssib le s u p p ly o f ra w m a te r i a ls ; a n d , fro m th o in d iv id u a l in o v e iy o c c u p a tio n , th e d e te r m in a tio n to e x e r t t h a t d e g re e of a d d itio n a l e ffo rt w h ich w ill su c c e e d in c h a n g in g th e p r o s ­ p e c ts of a p p ro a c h in g eco n o m ic d is a s te r in to th o s e w h ic h w ill e n s u re n a tio n a l s ta b ility a n d , fin ally , p ro s p e rity . I n d u s t r y ’s U n h e e d e d W a rn in g s T H E w o rd crisis is to - d a y , to o freely , u sed , in t h a t th e r e is n o th in g in o u r p r e s e n t e m b a r r a s s m e n t w h ic h h a s n o t b e e n e x p e c te d . T h o se w ho c o n tro l o u r d e s tin ie s h a v e c a lle d i t th e e le v e n th h o u r, a n d if w e a c c e p t t h a t d e s c rip ­ tio n a s c o r r e c t i t m u s t b e b e c a u se th o w a rn in g s of in d u s tr y , lik e th o s e w h ic h p re c e d e d th o fu el crisis, h a v e n o t b e e n h e e d e d . I f i t is th e e le v e n th h o u r of a crisis, i t is also t h a t h o u r w h e n m ig h t b e e x p e c te d a c le a r d e c la ra tio n of th e f a c t s of o u r in d u s tr i a l p o sitio n , a n d a re m o v a l o f t h e r e d ta p e a n d f e tte r s w h ic h r e s tr a i n th e w h e e ls o f in d u s tr y a n d o p p re s s th o s e e n g a g e d in tu r n in g th e m . I t is th o h o u r fo r le s s ta l k ; fo r less m u d d lè d th in k in g ; fo r m o re n a tio n ; a n d m o re w o rk .

T e c h n ic a l T r a i n i n g a n d R e s e a r c h I N view' of th e I .E .E . R e p o r t o n th e p ra c tic a l tr a in in g of p ro fessio n al en g in ee rs, a n d o u r re m a rk s u p o n i t in Th e Elec tr icia n of J u l y 18 la st, i t is of in te r e s t to n o te t h a t th e r e h a v e b e e n s u b m itte d to t h e L o r d P r e s id e n t of th e C ouncil a n d t h e M in iste r o f E d u c a tio n , th e re c o m m e n d a tio n s o f th e P a r l ia m e n ­ ta r y a n d S cientific C o m m itte e w ith re s p e c t t o colleges o f te c h n o lo g y a n d t h e tr a in in g of te c h n ic a l m a n -p o w e r. I n effect th e re c o m m e n d a tio n s c o n firm th e fin d in g s o f th e e le c tric a l in d u s tr y , t h a t in o rd e r to re s to re a n d e n h a n c e o u r in d u s tr ia l p o sitio n , i t is n e c e ss a ry fo r re s e a rc h n o t o n ly to b e c a rr ie d o u t a s w id e ly a n d a s e x te n s iv e ly a s p o ssib le, b u t to e n s u re t h a t i t s re s u lts a r e a p p lie d p r o m p tly to p ro d u c tio n . B e fo re th is c o n ­

THE ELECTRICIAN IS A U G U ST 1947

461 d itio n c a n bo b r o u g h t a b o u t, h o w ev er,

th e tr a in e d o u t p u t of o u r te ch n o lo g ical colleges m u s t b e su ffic ie n tly k n o w led g e­

a b le to a p p re c ia te th e in d u s tr ia l a p p lic a ­ tio n s o f s u c h re s e a rc h , itho n u m b e r of g r a d u a t e s of s u c h colleges m u s t b e in ­ c re a s e d to a t le a s t d o u b le its p re s e n t figure, w h ile t h e s ta n d a r d of tra in in g w ill n e e d to h e ra is e d to o n e a p p r o a c h ­ in g t h a t s e t b y t h e u n iv e rs itie s . A d e q u a c y o f T e a c h in g S ta ff T E C H N IC A L tr a in i n g is f u r th e r c h a m ­ p io n e d b y th e I .E .E ., fo r in a special r e p o r t, a b s t r a c t e d in la s t w e e k ’s issue, th o q u e s tio n of r e s e a rc h in th e ra d io field w a s c o v e re d . H e re , a s in o th e r b r a n c h e s of in d u s tr y , th e e a rly a v a il­

a b ility o f re s e a rc h r e s u lts is e m p h a ­ sised, a n d th o su g g e stio n is p u t fo rw a rd of d is s e m in a tin g d e ta ils of re s e a rc h w o rk th r o u g h so m e fo rm of b u re a u .- A m o n g th e d iffic u ltie s w inch h a v e to bo o v e rc o m e b efo re itho colleges c a n ibe e x p e c te d to in c re a s e th e n u m b e r of g r a d u a t e s a v a ila b le to in d u s tr y , h o w ­ ev er, is t h a t c o n c e rn e d w ith te a c h in g s ta ll. T h o o p p o rtu n itie s p re s e n te d b y s u c h colleges a r e few w h e n c o m p a re d w ith e ith e r th e u n iv e rs itie s o r in d u s try , a n d u n til a p p o in tm e n ts in th e m a r e m a d e m o re a t t r a c t i v e th e r e is a d a n g e r t h a t th e re c o m m e n d a tio n s so o fte n m a d e by th e e le c tric a l in d u s tr y , th o en g in ee rin g in s titu tio n s a n d o th e rs , m a y n o t b e as w id e ly a d o p te d a s is h o p e d th r o u g h sh eer in a b ility to fin d e n o u g h te c h n ic a l te a c h ­ in g s ta ff to c a rr y th e m o u t.

E l e c tr o n ic A ids to P r o d u c t i o n H O W a m o re w id e s p r e a d u se o f elec­

tr o n ic d e v ic e s in in d u s tr y w o u ld le a d t o a g r e a tly in c re a s e d o u t p u t o f m a n u f a c tu r e d g o o d s a n d so a s s is t m a te ria lly in o v e r­

c o m in g th e p r e s e n t eco n o m ic crisis, is in d ic a te d b y D r. H . A. Th o m a s, p rin c ip a l sc ie n tific officer' in th e R a d io D iv isio n of t h e N a tio n a l P h y s ic a l L a b o ra to ry , in a n a r tic le h e a d e d “ E le c tro n ic s a s a n A id t o P r o d u c tio n ,” in a r e c e n t is su e of th e B o a rd o f T r a d e J o u r n a l. A s he p o in ts o u t, th e c o r r e c t a p p lic a tio n of e le c tro n ic te c h n iq u e le a d s n o t o n ly to g r e a te r p ro d u c tio n p e r m a n -h o u r, b u t effects v e ry im p o rta n t- im p ro v e m e n ts in th e q u a lity a n d c o n siste n c y -o f t h e m a n u ­ f a c tu re d p ro d u c t. T h e q u a n t i t y o f elec­

tro n ic e q u ip m e n t n e e d e d is sm all, th e c o s t is n eg lig ib le in c o m p a ris o n w ith th e im p ro v e d o u t p u t w h ic h c a n b e o b ta in e d , a n d th e r e a r e a v a ila b le m a n y e le c tro n i­

c a lly -m in d e d en g in ee rs, c a p a b le of d e ­ v e lo p in g su c h e q u ip m e n t. T h e m a in re a s o n w h y s u c h te c h n iq u e s h a v e n o t b e e n m o re g e n e ra lly a d o p te d , is a t t r i b u t e d b y D r.

Tho m as to t h e f a c t t h a t in d u s tr y is n o t y e t a w a re o f t h e p o te n tia litie s o f elec­

tro n ic en g in ee rin g , a n d d o c s n o t re a lise th e e n o rm o u s p o ss ib ilitie s of a p p ly in g th is n ew a i d ; a n d , to a lesser d eg ree, to th e f a c t .th a t th e m a n u f a c tu r e r s of elec­

tro n ic e q u ip m e n t a r e n a tu r a ll y a v e rs e to d e v e lo p in g a t th e ir ow n e x p en se e q u ip ­ m e n t w h ic h m a y h a v e a n u n c e r ta in or lim ite d m a r k e t. D r. Thom as su g g ests t h a t i t is o n ly b y b rin g in g to g e th e r th e in d u s tria l s c ie n tis t a ss o c ia te d w ith th e d e v e lo p m e n t o f a p a r tic u la r p ro d u c t, a n d th o e le c tro n ic “ e x p e r t,” w h o u s u a lly is u n fa m ilia r w ith th o p r a c tic a l p ro b le m s of p ro d u c tio n , t h a t p ro g re ss w ill b e m ad e.

I n Ithe in t e r e s t s o f th e n a tio n a l eco n o m y s u c h e le c tro n ic “ e x p e r ts ” s h o u ld be g iv e n w id o sc o p e to a p p ly th e ir sp ecialised k n o w led g e to im p ro v e in d u s ­ tr ia l processes.

T h e T r a n s p o r t C o m m i s s i o n T H E a p p o in tm e n t o f S ir Cy r il Hu rcom b

to th e c h a ir m a n s h ip of th e T r a n s p o r t C om m ission, m e a n s t h a t so o n e r o r la te r th e in d u s tr y w ill lose a n o ld frie n d . A s c h a ir m a n of th e E le c tric ity C o m ­ m issio n , S ir Cy r il h a s m a in ta in e d a s p ir it of c o -o p e ra tio n a n d u n d e r s ta n d in g w ith th e in d u s tr y th r o u g h o u t m a n y y e a rs of o u ts ta n d in g difficulties, a n d m a n y w ill m iss h im . A n o th o r e le c tric a l p e rs o n a lity fro m a n a d m in is tr a tiv e p o i n t o f v iew is L o r d As h f ie l d, w ho, a s t h e p io n e e rin g s p ir it b e h in d th e L o n d o n U n d e rg ro u n d , m a d e o u r sy s te m th e e n v y o f th e w o rld . H e, to o , is d e s tin e d fo r t h e T r a n s p o r t C om m ission, th o u g h in h is case h is n ew re s p o n sib ilitie s w ill n o t b e so v e ry d iffe re n t fro m th o s e h e a t p r e s e n t c a rrie s a s c h a ir m a n of L o n d o n T r a n s p o r t. T h o n a tu r e o f th e s e n e w a p p o in tm e n ts will e n su re th e ir h o ld e rs m a k in g a t least so m e c o n tin u e d c o n ta c t w ith e le c tric a l in d u s tr y , fo r a m o n g , t h e p ro b le m s of ro a d a n d r a il w h ic h c o n f r o n t th e m a re th o s e c o n c e rn e d w ith t h e f u r th e r a n c e of ra ilw a y e le c trific a tio n a n d e n c o u ra g e ­ m e n t in th e u se of th e e le c tric v ehicle.

ry AU G U ST 1947 THE ELECTRICIAN

A b o u t T r a n s f o r m e r s

b y G . O . C A S T E E L , M . L E . E .

D e s i g n a n d C o n s t r u c t i o n o f t h e C o r e

This is P a rt I o f a series o f articles in w hich th e a u th o r w ill discuss a nd describe the m aterials u sed in th e design a nd construction o f pow er transform ers. M ethods o f m a n u ­ fa ctu re, processes in v o lv e d , a n d th e tests to w h ich b o th m aterials a nd com ponents are p u t, w ill be referred to as the series progresses, to g eth er w ith explanations of how

various engineering problem s relating to transform ers are overcom e.

T

t r y are of th e “ c o re ” ty p e of construction, w ith coils w'ound on circular m andrels and cores b u ilt w ith vario u s w id th s of plate, all, how ever, w ith in a circular perim eter.

I n p o in t of fa c t, th e b e st u se of th e m aterials is m a d e if th e core is rectan g u ­ la r in sh ap e w ith a ra tio of len g th to b re a d th of a b o u t 1.8 to 1 ; th e round coil, how ever, h a s th e a d v a n ta g e of superior m echanical s tre n g th , while i t is easier to w ind a n d to in su late, is m ore likely to be dim ensionally c o n sta n t in m an u factu re, an d cooling is generally m ore efficient. I n th e case of large tran sfo rm ers, m echanical s tre n g th is a n over-riding consideration, b u t fo r sm all tran sfo rm ers, of high effici­

e n cy such as form th e b u lk of th e distri­

b u tio n u n its in A m erica a n d C anada, a rectan g u lar coro is in v a ria b ly used. T he cost of th e co m p arativ ely large q u an tities of iron a n d copper necessary to obtain th e desired efficiency, sw am ps th e e x tra labour charges entailed b y th is form of co n stru ctio n , w hile th e m aterials are w orked a t such conservative loading t h a t cooling p resen ts no problem s a n d th e m echanical forces m e t w ith in d istrib u tio n sizes are n o t serious.

F o r th e purposes of th is series of articles, how ever, consideration will be given to th e s ta n d a rd p ractice in th is co u n try , a n d th is im plies th e use of ro u n d cores.

Core D im ensions.—E v e ry s tu d e n t is, essum edly, fam iliar w ith K a p p ’s P ropor-

VARNISH

RUBBER R O L L E R S

th ese p rovide a useful guide, b u t p ractical necessity lim its th e designer to a n u m b er of s ta n d a rd core sections a n d p ro b ab ly a n u m b e r of s ta n d a rd leg lengths a n d leg centres fo r each section. Peculiarities of custom ers’ specifications, such as n o n ­ s ta n d a rd reactan ces o r u n u su al ratio s of

copper loss to iro n loss, fu rth e r confuse th e use of th eo retical fo rm u la . I n ad d itio n , alth o u g h m a n y of th e form ula! includo th e cost of copper a n d core steel, th e a u th o r h as y e t to see one w hich ta k e s in to acco u n t th e cost of insulations, c o n stru ctio n al steel a n d oil, all of w hich affect th e final deci­

sion. T h e choico of core dim ensions is alw ays th e offspring of tria l a n d erro r o u t of experience.

Core Circle S tep s.—H a v in g decided u p o n a ro u n d core of th e form illu s tra te d in Fig. 1, i t h a s to be decided how m a n y different w id th s of core p la te to em ploy, or, a s i t is m o re com m only expressed, how m a n y step s to p u t in to th e core circle.

Again, th e designer h as to arriv e a t th e

FU RNACE Re s i s t o r s -e a c h WITH

THERMOSTATIC CONTROL

\ ( 0 ) = = H

CONVEYOR

* * * *■ — --- " ’ COREPtATESII

V A R N IS H S U M P

Fig. 2

tions a n d vario u s o th e r form ula; w hich p ro ­ vide a th eo retical or a n em pirical m eth o d of arriv in g a t th e various dim ensions of th e

core fo r a n y given transform er. Some of o p tim u m betw een p ractical considerations a n d th e b e st use of th e basic m a te ria ls ; th e

THE E L E C T R IC IA N IS A UG U ST 1947

form er w ould d ic ta te one p late w id th , th a t is a sq u are core w ith in a ro u n d coil, while th e la tte r w ould req u ire every p late to bo of slightly different w id th to th e n e x t, so o b tain in g a tr u ly ro u n d core w hich would,

of course, p rovide th e m axim um useful section from an y core circle. U sually three, fo u r o r five step s are fou n d to

b e b e st, depending o n th e size of th e tran sfo rm er a n d th e re la tiv e costs of core steel an d labour.

U nless th e core steel is to bo re-an n ealed a f te r c u ttin g a n d p u nching, tire u se of vory n arro w p lates to o b ta in th e m ax im u m of iron section w ith in th e circle d e fe a ts its own o b ject. A sm all area a d ja c e n t to a c u t edge is affected' b y th e to o l b o th as to p erm eab ility a n d loss characteristic, a n d in n arrow p lates th e affected p o rtio n b e ­ com es an ap p reciab le p ro p o r­

tio n o f tho w hole a n d th e de­

signed figures will n o t be m a in ta in e d on te s t.

Dimensions of S te p s T here is a sim ple m a th e m a tic a l ex­

pression giving th e dim en­

sions of th e various step s to

o b ta in tire m ax im u m of iron section fo ran y given n u m b e r of step s, b u t again practical

DUCTS

IS A U G U ST 1947

necessities jostle w ith th eo ry . T hocore steel com es from tho suppliers in sheets of s ta n d a rd sizes a n d m u s t be c u t w ith a m inim um of w astag e; ideally, every core p lato w id th should be a n e x a c t divisor of th o sh e e t -w idth; if n o t, vario u s com bina­

tions of p la te w id th m u s t divide ex actly in to th e sh e e t w id th , b u t in tho la tte r ease th o p ro p o rtio n ate am o u n ts of th e various p lato w id th s re q u ire d a n d /o r o b tain ed m u s t b e b o rn e in m in d .

Tho yokes o r horizontal m em bers of th e m agnetic circu it, connecting th e vertical lim bs to g eth er, to p a n d b o tto m , are com­

m only m ade larg er in section u p to a b o u t fifteen p er c e n t .; tin s being a m eth o d of red u cin g th e iron loss w ith o u t affecting th e len g th of th o w inding tu rn s . If a g reater red u ctio n in loss is a tte m p te d b y fu rth e r increasing th e yoke area, th e

463

m eth o d fails b ecause th e effect of th e longer len g th of flux p a th th ro u g h th e u p p e r areas of th e yoke becom es notice­

able, a n d th e flux te n d s to crow d in to t h a t p a r t of th e core a d ja c e n t to th e lim bs.

W h a te v e r th e p ro p o rtio n of yoke a re a to leg area, th e various p a c k e ts in th e y oke m u s t b e a r th e sam e relatio n sh ip to th e corresponding p a c k e t in th o lim b, o therw ise cross fluxes w ill develop a t th e jo in ts, causing increased lo s s e s 'a n d m ag ­ netising c u rre n t, th e risk of local h eatin g a n d a n increase in noise.

A b o u t h alf th e noise p roduced b y a tran sfo rm er core in n o rm al op eratio n is duo to m ag n eto -strictio n a n d this" can only b e red u ced b y low ering th e w orking flux d en sity . T ho rem ain d er is produced a t th e jo in ts an d can b e -m in im ise d b y careful building, rigid clam ping a n d th e elim ination of cross fluxes. A com plete

THE ELECTRICIAN Fig. 5.— Core o f 45 M V A transformer

tran sfo rm er will produce o th e r extraneous noises from leads a n d fittings, b u t th is will bo discussed elsewhere.

Core Losses.—T he loss in a core w hen i t is ex cited consists in p a r t of hysteresis

Fig. 8.— Core for transformer of I 000 k V A , showing simple limb bolting

ran d o m sam ples m u s t b e te s te d every d a y , for thickness of film a n d in su latio n v a lu e ; ty p ic a l values are a film of three- te n -th o u sa n d th s of a n in ch in thickness w ith a break d o w n vo ltag e of 200 V. A th ic k e r v arn ish film is likely to b e im p er­

fectly sto v ed a n d possibly ta c k y ; th e in- 15 A U G U ST tV4?

Fig. 7.— Core o f sm all transformer, showing limb bound with webbing tape

loss, of w hich th e frequency of th e su pply voltage, th e m axim um v alu e of th e flux d e n sity a n d th e n a tu re of th e m aterial are c o n trib u to ry facto rs. T h e balance consists of e d d y c u rre n t loss w hich de­

pends up o n th e freq u en cy , th e flux density, th e ohm ic resistance of th e core steel a n d th e thickness of th e lam inations.

F o r th is reason th e sheets a re m a d e as th in as can bo econom ically produced, a n d conveniently h an d led b y th e tr a n s ­ form er m a k e rs; 14 m ils, is th e thickness in general use for pow er tra n sfo rm e rs;

lam inations of 7 m ils, thickness h a v e been produced for h ig h freq u en cy applications an d th e stam pings u sed for sm all tr a n s ­ form ers designed fo r rad io frequencies, are 4 m ils, th ic k ; th e p ro d u c tio n costs fo r th e th in n e r sheets increase v ery rapidly.

I n a m od em core of 14 m ils, th ick lam inations, th e ed d y c u rre n t losses re p re ­ se n t a b o u t tw e n ty p e r cent, of th e to ta l loss a t fifty cycles.

Cere P late Insulation.—-The red u ctio n in eddy c u rre n t losses b y lam inating th e core can only bo o b tain ed if e v ery core p late is effectively in su lated from th e n e x t; p ap er, v arn ish , enam el an d various m ix tu res of chalk, flour, isinglass and kaolin h a v e all been used fo r th is purpose.

P a p e r requires a n extensive p la n t for its app licatio n to th e sheet. I t , in itself, occupies a com paratively large area of th e core giving a space fa c to r of only a b o u t eighty-five p e r c e n t., a n d i t is liable THE ELE C TR IC IA N

to b reak dow n quick ly if a h o t sp o t should develop in th e core. P a p e r, like th e m ix­

tu re s m entioned, w hich are usually applied w ith a sp ray , can only be applied conveniently to th e original sh e e t; enam el a n d v a rn ish are, on th e c o n tra ry , u su ally applied to th e core p la te s a fte r c u ttin g a n d puneliing, w hich m eans t h a t all th e cu t edges a re in su lated . T h is w ould b e of no g re a t im p o rtan ce if every core w ere p erfectly c u t, p u n ch ed a n d assem bled, b u t it provides a v ery real safeg u ard in th is im p erfect w orld w here m in u te b u rrs som e­

tim es a p p e a r on th e edges a n d holes ju s t a little o u t of alignm ent.

F ig . 2 show s, in outline, a ty p ical p la n t fo r v a rn ish in su latin g of core p la te s ; the lam inations are fed th ro u g h pow er driven ru b b e r rollers w hich are co n sta n tly s u p ­ plied w ith v a rn ish from th e ta n k above.

T he p ressu re a n d speed of th e rollers an d th e te m p e ra tu re a n d viscosity of th e v arn ish m u s t all b e carefully controlled if a film of c o n s ta n t thickness a n d con­

sistency is to be o b tain ed . F ro m th e rollers th e core p la te s pass on to a con­

vey o r b e lt w hich tra v e ls th ro u g h a tu n n e l fu rn a c e ; th is ■ m ay b e h e a te d b y gas bu rn ers, electric resistors or in fra rod, b u t i t m u s t be th e rm o sta tic a lly controlled, in stages, th ro u g h o u t its len g th . A b a tc h of

su latio n value m ay a p p e a r satisfacto ry , b u t of solid in sulation, such as 10 mil. thick it w ould d e te rio ra te w hen clam ping pres- p ressboard, a t fre q u e n t in te rv a ls th ro u g h - su re w as applied to th e c o re ; a th in n e r film

will n o t record a satisfacto ry insulation valu e.

I f th e core p la te s are to be reannealed a f te r c u ttin g a n d p u nching, i t m u s t bo e a rn e d o u t before th e in su latin g process, w hich is, of course, im possible in th e case of those m aterials ap p lied to th e original sh eet. R ean n ealin g is carried o u t in an in e rt atm o sp h ere a t a te m p e ra tu re of a b o u t 700° C.

Building th e Core. W hen th e p la te s have been p re p a re d th e cores are b u ilt by h an d . T h e core clam ps a n d flitch p lates are a r ­ ran g ed in a jig on a su itab le ta b le w ith u p rig h t p in s of th e a p p ro p ria te d iam eter a n d co n v en ie n t len g th in th e b o lt holes;

th e core p lates are th re a d e d over th e pins.

T he jo in ts betw een th e core legs an d the yokes are , in m o d ern tran sfo rm ers, in ­ v a ria b ly of th e in ter-leav cd ty p e ; th is is o b ta in e d by overlapping th e p lates suc­

cessively in opposite d irections, as depicted in Fig. 3, w herein, fo r clarity , th e plates h ave b een d raw n of ex ag g erated thickness.

B e st electrical re su lts w ould bo o btained if th e lam inations w ere to bo interleav ed singly, b u t i t is general p ra c tic e to build th e cores w ith lam inations in tw os, threes o r fo u r s ; th is sh o rten s th e tim e required fo r building a n d reduces th e chances of buckling p lates.

Coro p la te s in su lated w ith p a p e r o r w ith . th e sprayod-on m ix tu re s are usually insu­

la te d on one side only of each sh e e t;

v arnish o r enam el ap p lied b y rollers covers

bo th sides of th e p la te a n d i t is usual '\S■ ID- Distribution transformer fo r C ana- th e n to b uild w ith in su la te d a n d uninsu- aian systems. The rectangular fo rm o f la tc d p la te s stack ed a lte rn a te ly . In addi- construction enables a very high electrical tion, it is good p ractico to in s e rt a sheet efficiency to be obtained

o u t th e d e p th of th e com . If this is done i t is im p o rta n t to m ake a n electrical connection in th e sh ap e of a sm all e a rth clip betw een each p a c k e t a n d th e n ex t.

W hen th e core h as been b u ilt u p to th e specified d e p th , th e second s e t of core clam ps a n d flitch p la te s is a d d e d ; bolts a n d th e ir in su latio n .are su b s titu te d for th e building pins a n d th e core is clam ped up. Sm all cores a m b u ilt as described, b u t w ith o u t th e to p yoke p lates being in ­ clu d ed ; larger cores are b u ilt a n d clam p ed .co m p lete a n d th e to p yoke p lates rem oved a fte r th e core h a s b een stood up- . r ig h t; in e ith e r case th e top y oke p lates h av e to be b u ilt in b y h a n d a fte r th e w ind- Fig. 9.—F la n t fo r applying varnish insulation to transformer ings h ave b een assem bled on

core lam inations th e legs.

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iy A UG U ST 1947 THE E L E C T R IC IA N