Regulated and controlled direct current electrical supply for laboratories

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NATIONAL RESEARCH COUNCIL CANADA

DIVISION OF BUILDING RESEARCH

A REGULATED AND CONTROLLED DIRECT CURRENT ELECTRICAL SUPPLY FOR LABORATORIES

by J.S, Keeler

(This r e p o r t has been prepared f o r information and r e c o r d purposes

and is not t o be r e f e r e n c e d i n any p u b l i c a t f o n )

Report No, 102 of t h e

Division of Building Research

Ottawa . O c t o b . e ~

1956

PREFACE

The e q u i p p i n g of modern l a b o k s t c k i e s r e q u i r e s much s p e c i a l e n g i n e e r i n g , Heat t r a n s f e r l a b o r a t o r i e s are no e x c e p t i o n , s i n c e t h e y requLTe b o t h h e a t s o u r c e s and h e a t s i n k s which can be

o p e r a t e d under c l o s e e o n t r o l , The a p p a r a t u s d e s - c r i b e d i n t h i s r e p o r t p r o v i d e s a s u i t s b l e eneFgy s o u r c e f o r many t h e r m a l experiments planned $6-

t h e l a b o r a t o r i e s of t h e B u i l d i n g Servdces Ssct.3 on

of t h i s D i v i s i o n , The way

i n which

t h e " s i c , Tegu- l a t o r and c o n t r o l l e r c i r c u i t d e v i s e d by Lbze

D i v i s i o n of Physics was used t o p r o v i d e a s u d t -

a b l e e l e c t r i c a l supply f o r a nwnber of s e l e c t e d s t a t i o s s throughout t h e l a b o r a t o s % e s , t o g e t h a s w i t h t h e r e c o r d ~ f t h e check made of performance,

may be of i n t e r e s t t o o t h e r s i n need of' s u c h

f a c i l i t i e s .

O t t a w a 9

A _REGULATED AND CONTRQLLED DIRECT CURRENT

ELECTRICAL SUPPLY FOR LABORATORIES by

J . S . K e e l e r

I n experimental h e a t t r a n s f e r work, a c c u r a t e energy meas- urements a r e n e c e s s a r y . Thermal energy i s o f t e n produced e l e c t r i c - a l l y and i t i s u s u a l l y convenient t o measure t h e t h e r m a l energy by measuring t h e e l e c t r i c a l i n p u t . I n t h i s r e s p e c t d i r e c t c u r r e n t h a s a n advantage over a l t e r n a t i n g c u r r e n t 8s i t can be measured more

e a s i l y . Also s i n c e t e m p e r a t u r e i s o f t e n measured w i t h thermocouples, t h e same p o t e n t i o m e t e r used t o measure t h m o - e l e c t r i c e , m . f O f s can be used t o measure h e a t i n p u t i f d-c. h e a t i n g i s u s e d ,

A c o n s t a n t h e a t i n p u t i s r e q u i r e d f o r h e a t t r a n s f e r equip- ment such a s t h e guarded hot p l a t e thermalL:conductivity a p p a r a t u s , t h e l i n e h e a t source ( t h e r m a l c o n d u c t i v i t y p r o b e ) , thermal models, and a p p a r a t u s f o r measuring t h e h e a t t r a n s f e r t h r o u g h b u i l t up w a l l

s e c t i o n s ( e . g . guarded hot b o x ) . It i s n e c e s s a r y t h e r e f o r e t h a t t h e d i r e c t c u r r e n t supply be w e l l r e g u l a t e d and e a s i l y c o n t r o l l e d . I n g e n e r a l , an u n r e g u l a t e d d - c . s u p p l y , such as t h a t i n t h e D i v i s i o n a l l a b o r a t o r i e s , shows s i z e a b l e f l u c t u a t i o n s i n t h e o u t p u t v o l t a g e due t o changes i n t h e a - c . l i n e v o l t a g e o r i n t h e d-c. l o a d , and hence

i s u n s a t i s f a c t o r y by i t s e l f where v o l t a g e s t a b i l i t y and p r e c i s e meas- urement a r e r e q u i r e d .

An e l e c t r o n i c d-c. r e g u l a t o r and c o n t r o l l e r , which r e d u c e s t h e s e f l u c t u a t i o n s by a f a c t o r of 100, and a t t h e same time p r o v i d e s convenient c o n t r o l of o u t p u t v o l t a g e h a s been developed by Dauphinee and Woods of t h e D i v i a i o n of Physics ( ~ e v . S c i . I n s t r . Vol, 26, No,

7,

p,693, J u l y 1 9 5 5 ) . Th&s u n i t g i v e s b e t t e r r e g u l a t i o n t h a n any s t o c k u n i t a v a i l a b l e , The o u t p u t c o n t r o l p e r m i t s continuous v a r i a t i o n of t h e v o l t a g e l e v e l OF t h e r e g u l a t e d d - c . o u t p u t over t h e range of 0 t o

70 v o l t s .

The b a s i c c i r c u i t ofi)Dauphl.nee and Woods r e g u l a t o r and c o n t r o l l e r i s being used wherever r e g u l a t i o n of t h e 110 v , d - c , s u p p l y

i s r e q u i r e d , modif i c a t i o n s having been made o n l y i n l a y o u t , swbtehing

,

power supply and e x t e r n a l c o n n e c t i o n s t o a d a p t i t t o t h i s Divi.signl s l a b o r a t o r y arrangement, When modif l e d , only a simple change i n e x t e ~ n a l c o n n e c t i o n s i s r e q u i r e d t o a l t e r t h e o u t p u t c a p a c i t y ,

It i s t h e purpoge of t h i s r e p o r t t o d e s c r i b e t h e a d a p t a - t i o n of t h e o r i g i n a l d e s i g n t o provide r e g u l a t e d d-c. power f o r t h e D i v i s i o n l s h e a t t r a n s f e r work and t o g i v e t h e r e s u l t s of performance t e s t s c a r r i e d out t o determine t h e l i m i t a t i o n s of t h e u n i t s ,

CIRCUIT AND CONSTRUCTION

The c i r c u i t s f o r t h e c o n t s o l l e r and r e g u l a t o r a s used i n t h e D i v i s i o n l s u n i t s a s e shown i n F i g , 1. For a d e s ~ r i p t i o n it I s

convenient t o break t h e c i r c u i t i n t o two parts,aibkiel P e g u l a t o r and t h e c o n t r o l l e r , and d i s c u s s each s e p a r a t e l y ,

1) The R e g u l a t o r Unit:-

The r e g u l a t i n g c i r c u i t c o n s i s t s simply of a number of 6A$7 G

t u b e s connected i n p a r a l l e l , t h e unregulated d - c , i n p u t being f e d t o t h e p l a t e s , and t h e r e g u l a t e d output being t a k e n from t h e cathodes, Operation of t h e t u b e s i s dependent on t h e v o l t a g e of t h e g r i d s which a r e connected i n p a r a l l e l w i t h t h e c o n t r o l l e r o u t p u t , The number of r e g u l a t i n g t u b e s used i s dependent on t h e l o a d , The experience of t h e D i v i s i o n of Physics has shown t h a t 0 , 5 amps. of r e g u l a t e d d-c, can be drawn from each tube without any apparent damage although t h i s i s somewhat h i g h e r t h a n t h e manufacturer's recommended maxl.mwn, Because c a p a c i t i e s of 2.5, 5 , 0 and 10,O amps, a r e convenient f o r t h e proposed a p p l i c a t i o n s a 5-tube module was chosen, F i g u r e 2 shows t h e p h y s i c a l layout of one 2 , 5 amp. r e g u l a t o r u n i t and t h e arrangement usect', The p a r t s a r e assembled on a 3$-inch panel c h a s s i s t h a t can be mounted i n a s t a n d a r d r e l a y rack i n conJunction w i t h a 33-inch r a c k p a n e l ,

E x t e r n a l connections t o each r e g u l a t o r c h a s s i s ape through a s i x t e r m f n a l chassis-mounted plug, which c a r r i e s t h e unregulated d-c, i n p u t , r e g u l a t e d d - c , o u t p u t , c o n t r o l l e r output t o t h e r e g u l a t o r g r i d , a grgund l e a d , and r e g u l a t o r f i l a m e n t s supply, I n c r e a s i n g t h e c a p a c i t y of any r e g u l a t o r i s a very simple o p e r a t i o n , Up t o f o u r w a i t s , connected i n p a r a l l e l , may be used w i t h one c o n t r o l l e r a s c o n s t r u c t e d , t h e n e a r e s t u n i t being connected d i r e c t l y t o t h e c o n t r o l l e r , and a l l o t h e r s t o t h e s i x t e r m i n a l socket on t h e preceding r e g u l a t o r , Thua t h e m a x i m u m c a p a c i t y i s _{10 amps.}

Each r e g u l a t o r f i l a m e n t draws 2 , 5 ampa, To reduce t h e t o t a l f i l a m e n t c u r r e n t t h e f i l a m e n t s a r e i n s e r i e s r a t h e r t h a n i n p a r a l l e l , Consequently, when more t h a n one r e g u l a t o r i s used, t h e f i l a m e n t t e r - minals of t h e socket on t h e l a s t r e g u l a t o r c h a s s i s must be joined t o

complete t h e c i r c u i t , A s h o r t e d plug i s convenient t o use f o r t h i s purpose.

A l l l e a d s t o t h e r e g u l a t o r s o r i g i n a t e i n t h e c o n t r o l l e r u n i t which houses, i n a d d i t i o n t o t h e c o n t r o l c i r ~ u i t , t h e lnput and output plugs and s o c k e t s , s w i t c h e s , p i l o t lamps, f u s e s , meters, and t h e f i l a m e n t power supply.

2 ) The C o n t r o l l e r Unit :

-

The c o n t r o l l i n g c i r c u i t c o n s i s t s of a two s t a g e a m p l i f i e r u s i n g a 6AU6

aham

c u t o f f pentode and a

6AV6

a s a t rlodie w i t h a cathode f o l l o w e r . Input t o t h e c o n t r o l l e r i s tapped from a 209000 o h r h e o s t a t which, i n s e r i e s w i t h an 82,000 o h r e s i s t o r , is connected

a c r o s s t h e m g u l a t e d d-c, output and t h e b i a s v o l t a g e , The p o a i t i o g of t h e s l i d e r i n t h i s r h e o s t a t d e t e r n i n e s the r e g u l a t o r output v o l t - a g e , To permit t h e a d d i t i o n of a n e x t e r n a l e,rn,f, t o t h e c o n t r o l grhd of t h e 6AUb a c h a s s i s plug, connected a c r s s a

a

s e r i e s r e s i q t a n c e In t h e g r i d c i r c u i t , i s provided. T h i s f e a t u r e of t h e c ~ n t r o l can be used i n conjunction w i t h thermocouples o r m y s i g n a l e,m,d". and a s t a b l e , h i g h g a i n d - c , a m p l i f i e r a s

a

c o n t r o l system,

A l l power s u p p l i e s r e q u i r e d by t h e r e g u l a t o r and cowtkollek a r e f e d through t h e c o n t r o l l e r w r i t . The p l a t e and b i a s v o l t a g e s f o r t h e c o n t r o l l e r arc s u p p l i e d from r e g u l a t e d power s u p p l i e s a t -1-300 and -300 v o l t a d - c O 9 while t h e unregulated d - c , comes from a g e n e r a t o r a t +110 v o l t s d - c , These t h r e e supply v o l t a g e s a r e switched t o g e t h e r , wfth t h e +110 v o l t d-c, f u s e d a t 2 , 5 amps. p e r r e g u l a t o r , The 110 v o l t a - c , , which s u p p l i e s a l l f i l a m e n t s , i s a l s o switched and f u s e d i n t h e c o n t r o l l e r e h a a s i s , The s e r i e s of connected r e g u l a t o r f i l a m e n t s 1s

s u p p l i e d by an a d , j u s t a b l e a u t o t r a n $ f o m e r 9 which can aceommodate a maxlrn~m of f o u r r e g u l a t o r units, The f i l a m e n t s of t h e c o n t r o l t u b e s

a r e s u p p l i e d from

a

30-volt t a p on t h e a u t o t ~ a n s f o r m e r through a 3A10 b a l l a s t t u b e , Also mounted i n t h e c o n t r o l l e r u n i t a r e a d - c , v o l t - meter and a d - c , m e t e r f n t h e r e g u l a t e d o u t p u t .

The p h y s i c a l layout of t h e c o n t r o l l e r u n i t ( F i g ,

3 ) h a s been

designed f o r easy assembly and s e r v i c i n g , The components a r e assembled

OR

a

53-inch panel c h a s s i s which i n conjunction w i t h a 5+-inch sack panel, can be mounted in a standard r e l a y pack,

THE LABORATORY INSTALLATION

The d-c, source of supply f o r t h e D i v f s i o n l s l a b o m t o r l e a

i s a n a - c , d r i v e n motor-generator s e t which d e l i v e r s nominal 110 v.d-c, It f s i n s t a l l e d i n

a

~rnall meehanlcal equipment room c e n t r a l l y l ~ c a t e d t o the h e a t t r a n s f e r l a b o m t o r f e s ,

The r e g u l a t o ~ s and @ o n t r o l l e r s require r e g u l a t e d p l a t e and b i a s v o l t a g e s u p p l i e s of 9300 and -300 v , d - c , These s u p p l i e s , a v a i l - a b l e commercially, a r e mounted adJaeent t~ t h e mot ox?-generator s e t , The unregulated 110 v , d - c , , 9300 and -300 v , d T c , a ~ d grolmd a r e d%s- t ~ i b u t e d t s t h e l a b o s a t o ~ i e s regu%r%ng r e g u l a t e d d - @ ,

,

and t e r m i n a t e i n Camon female f o u r e f r c u i t o u t l e t s t o wh$ch t h e ~ e g u l a t s k and c o m t ~ o l l e r wit8 can be d l ~ e c t l y connected as r e q u i r e d ,

F i g u r e s 4,

5

_and b a r e photographs of one r e g u l a t o r and

c o n t r o l l e r e ~ m b l n a t f o n mounted i n a desk-type r e l a y r a c k , which sup- p ~ i e s r e g u l a t e d d - @ , power t o t h e 18-inch guarded hot p l a t e thermal conductLvfty a p p a r a t u s , Figure 4 i s a view of t h e f r o n t panels of two c o n t ~ o l l e r s and f o u r r e g u l a t o r $ , The lower p a r t of t h e r e U y s a c k c o n t a t ~ s t h e c o n t r o l panel f o r t h e hot p l a t e a p p a r a t u s , Figure 5 _{i s a r e a r view showing t h e e x t e r n a l connections and F i g ,} b shows

PERFORMANCE TESTS

P e ~ f o m a n c e te s t s were PU on a s i n g l e 2 , 5 amp, c o n t s o l l e r - s e g u l a t o r combl,nation t o determine i t s o p e r a t i n g c h a r a c t e r f s t i c s ,

The r e g u l a t e d output v o l t a g e was observed while t h e m.regu-

l a t e d I n p u t , t h e d - c , l o a d and t h e s e t t i n g of t h e c o n t r o l heo oat at

were var%ed i n d i v i d u a l l y , Tnput v o l t a g e covered a 40 v o l t range f r o m

90 t o 130 v o l t s d - c , i n 1 0 - v o l t s t e p s ; t h e d - c , load was v a r i e d fkow no load t o rnaxlmum

i2,5

amps, d - c , i n 5 s t e p s ; and the r h e o s t a t s e t - t i n g covered t h e f u l l mnge of 10 t u r n s

in 5 s t e p s ,

The output v o l t - age was measwed t o withfa? 0 , O l v o l t s d - c , oh a l a b o m t o r y potentiome- t e r , The load acd i n p u t were measured t o w i t h i n 0 , 0 1 amps, and 1 , O

v o l t s r e s p e c t i v e l y , while t h e c o n t r o l r h e o s t a t could be s e t t o w i t h i n 21500 o f a t u r n , (0.02 p e r c e n t of i t s s c a l e ) ,

F ~ o m t h e o b s e r v a t i o n s made i n t h i s s e r i e s of t e s t a a number of performance curves were p l o t t e d ( F i g s , -7 t 3 0 101, Figuke 7 shows t h e r e l a t i o n s h i p between output v o l t a g e and t h e s e t t i n g o f t h e c o n t r o l r h e o s t a t f o r an input, of 110 v ~ l t s d-c, Depa-tures of t h e half l o a d and f u l l l o a d curves from t h a t f o r no l o a d , a r e dare t o s a t u r a t i o n . i n t h e ~ e g u l a t o ~ t u b e s , T h i s e f f e c t i s b e t t e r i l l u s t r a t e d in F i g o 8, *

which shows t h e max%mm output v o l t a g e f o r all. c u r r e n t s up t o f u l l l o a d , Again t h i s i s based on an i c p u t of 110 v o l t s . Here t h e e f f e c t of s a t u r a t i o n i s q u i t e marked, A t a l o a d of l , 2 5 amps,

$

f u l l l o a d 9 t h e output v o l t a g e s t a r t s t h e s t e a d y drop which t a k e s i t t o 55 v o l t s m x i m m a t f u l l l o a d , The maximum power output t h e n i s

160

watts p e r r e g u l a t o r ~ r n - i t ,

Figure g ~ h o w s , on a percentage b a s i s , t h e v o l t a g e r e g u l a - t i o n f o r i n p u t v o l t a g e v a r i a t i o n s up t o 28 v o l t s e i t h e ~ s i d e of t h e 110 v o l t d-c, b a s e , The curves a r e p l o t t e d f o r half l o a d , 1 , 2 5 amps, and

3

s e t t i n g s of" t h e ~ u t p u t r h e o s t a t , Again t h e e f f e c t of s a t u r a - t i o n is e v l d e n t causing very poos r e g u l a t i o n f o r low v o l t a g e i n p u t s on t h e h i g h output v o l t a g e s e t t i n g s , Otherwise t h e v a r l a t i o n a i n output v o l t a g e a r e l e s s t h a n of 1 p e r c e n t f o r an i n p u t v o l t a g e changing as much as

5

v o l t s e i t h e r way, POP t h e 6,00 s e t t i n g , t h i s

i s a c t u a l l y l e s s t h a n 1/10 gf 1 p e r cent, POT s m a l l e r l o a d s r e g u l a - t i o n a t t h e h f g h e ~ s e t t i n g s is somewhat impsoved,

Zn

term9 of reduc- t k o n f a c t o r s p changes

i n

output v o l t a g e a r e g e n e r a l l y about 1/100 of t h o s e I n i n p u t v o l t a g e s ,

Voltags r e g u l a t i o n w i t h changing l o a d a t 110 v o l t i n p u t i s

i l l u s t r a t e d 1.n F i g , 10, a g a i n on a percentage b a s i s , The r e g u l a t i o n a t h i g h l o a d s w i t h t h e h i g h e r s e t t i n g s i s poos; however m t p u t v o l t - age variations a t t h e lower s e t t i n g s a s e l e s s t h a n

13

p e r c e n t ovey t h e f u l l Load range, T h i s i s poorer r e g u l a t i o n t h a n is shown 3ra _{P i g ,} 9 , but as t h e l o a d remains e s s e n t i a l l y c o n s t a n t f o ~ extended d e f i n i t e p e r i o d s , i n a11 intended a p p l c a t i o n s , t h i s a s p e c t of t h e p e r f o m a r ~ ~ ~ e is somewhat l e s s s i g n i f i c a n t O 1 G e n e r a l i z i n g , a 50 p e r c e n t i n c r e a s e

Supplementing t h e s e p e r f o ~ m n c e t e s t s , t h e e f f e c t off vas- f a t i o n s i n t h e ground p o t e n t i a l caused by voltage drop i n t h e groar*?d l e a d was observed. It was found t h a t over t h e f u l l - r a n g e of putput v o l t a g e , a change of 1

5

of a v o l t i n ground p o t e n t i a l changed t h e

/'

output by l e s s than 1 1 0 p e r c e n t . QONCLUSIQMS

The performance t e s t s have shown t h a t t h i s c o n t r o l l e r - r e g u l a t o r assembly produces an e x c e p t i o n a l l y w e l l r e g u l a t e d d i r e c t c u r r e n t voltage from a poorly r e g u l a t e d supply, I t s output v o l t a g e i s continuously a d j u s t a b l e over a l a r g e range, while

i t s

c a p a c i t y , which i s r e l a t i v e l y l a r g e , can be changed i n s t e p s by simple a l t e r -

a t i o n s i n t h e e x t e r n a l connections, One l i m i t a t i o n i s t h e decrease i n t h e maximum output voltage a t t h e higher loads due t~ s a t u p a t i o n of t h e r e g u l a t o r t u b e s , The optimum output v o l t a g e range f o r b e s t r e g ~ ~ l a t i o n 13 from 40 t o

55

v o l t s , The c o s t i s moderate, and t h e

constvuotion, i n s t a l l a t i o n and o p e r a t i o n a r e s t r a i g h t f o r w a r d , Per- haps t h e only drawback i n t h e ,system a s a whole i s t h e need for e x t e r n a l r e g u l a t e d p l a t e and b i a s voltage s u p p l i e s . These s u p p l i e s a r e r e l a t i v e l y expenaive and i f only one r e g u l a t e d supply was r e q u i r e d it w ~ u l d make a c o s t l y i n s t a l l a t $ o n , However, only one +300 and one -300 v , d ~ c , source @ r e needed t o supply a l a r g e number of ~ e g u l a t o r a and c o n t r o l l e r s , and t h i s t h e r e f o r e becomes a l e s s i m p o ~ t a n t consdd- e r a t i o n when s e v e r a l r e g u l a t e d s u p p l i e s a r e r e q u i r e d ,

I n conclusion, t h e r e g u l a t o r s and c o n t r o l l e r s described i n t h i s r e p o r t s a t k s f i e d t h e sequirements of t h e D i v i s i o n l a heat t ~ a n s f e r l a b o r a t o s l e s f o r r e g u l a t e d d-c

.

power,

FLg. 4 A vie\>$ cf the f r o n t p a n e l s

off the twe c o n L r o l l e r s and r o u r r e g u l a t c r s .

P l g .

5

A r e a s v i e w ~f Pfgure

4,

showing the external con-

F i g .

6

A more d e t a % l e d v i e w sf t h e c s w t s s ~ -

4.00 6-00 8.00 10-00 12~00

OUTPUT SETTING

L 0

FIGURE 7

LOAD

c

0 AMPS

LOAD

r:

1-25 AMPS

INPUT

=

110V. D.C.

,/

-- D B R R E P O R T 102

.

,.

I 1 INPUT

-

I I O V D.C. L

0

0

_1.0

FIGURE

8

2 . 0 D B R R E P O R T 102

COUTPUT S E T T I N 3

₌

2 . 0 0 INPUT = l I 0 VOLTS

-

D.C. VARIATION IN OUTPUT BASED ON OUTPUT AT 1-25 AMP. LOAD 0-

5

1.0

1.5

2 . 0

LOAD PER REGULATOR I N AMPS 0-C.

FIGURE

10