Variation of control characteristics of power thyratron tubes with frequency
by H W Snyder
A THESIS Submitted to the Graduate committee In partial fulfillment of the requirements for the
degree of Master of Science in Electrical Engineering
Montana State University
© Copyright by H W Snyder (1949)
Abstract:
A study was made of the variation in the control characteristics of three electrode thyratron tubes
operation at frequencies up to 1080 cycles per second. Tests were made on thyratron tubes in half-wave
rectification with magnitude d-c grid voltage control. The existence of two control characteristics, a
starting control characteristic and an extinguishing control characteristic, at higher-than-power
frequencies was confirmed. The starting control characteristic was determined to be dependent uoon
frequency of spoiled anode voltage, lnterolectrode capacitance, and tube "dark" currents which are
determined by geometry of electrode structures. Extinguishing control characteristic was found to be a
tube deionization phenomenon. VA IATION 07 CO-T OL GHA . 4CT2B I3 TIC5 OF
'OmLA THYKATAOw TJDGJ AlTH FRGQJZNCY
by
H. - .
'JYDaR
A THESIS
S u b m itted to th e G raduate Committee
In
p a r t i a l f u l f i l l m e n t o f th e r e q u ire m en ts
f o r th e d e g r e e o f
M aster o f S c ie n c e i n E l e c t r i c a l E n g in e e r in g
at
Montana S t a t e C o lle g e
Ap roved:
In Charge o f Major Work
Bozeman, Montana
J u n e 9 19^9
V sl^ l8 ,
Cu- i X
-
2 -
TABLE OF CONTENTS
A b s tr a c t e ................................................................................................ .......
I n t r o d u c t i o n .......................................................................................
4
H i s t o r i c a l S u r v e y ..............................
5
D e s c r i p t i o n o f T e s t E qu ipment and
P ro c e d u r e . . .
S t a r t i n g C h a r a c t e r i s t i c s . ....................
Pest R e s u l t s ,
R x t i n g u l a l l n g C h a r a c t e r i s t i c s ........................
7
9
20
C o n c l u s i o n s .............................................................................................24
A ppendix I
....................................................
A puendix I I
Ap end I x I I I
. . . . . . .
.
...........................................
. .........................................................
89332
-39
42
43
- 3 ABJTRACT
A s t u d y wae reads o f t h e v a r i a t i o n i n t h e oo i t r o l
c h a r a c t e r i s t i c s o f t h r e e e l e c t r o d e t h y r a t r o n t u b e s oper­
a t i o n a t f r e q u e n c i e s up t o 1030 c y c l e s p e r s e c o n d .
T ests
were made on t h y r a t r o n t u b e s i n h a l f - w a v e r e c t i f i c a t i o n
w ith magnitude d - c g r i d v o l ta g e c o n t r o l .
two c o n t r o l c h a r a c t e r i s t i c s ,
The e x i o t l n c o o f
a s ta r tin g control character­
i s t i c and an e x t i n g u i s h i n g c o n t r o l c h a r a c t e r i s t i c , a t
h i g h e r - t h e n - p o w e r f r e q u e n c i e s was c o n f i r m e d .
The s t a r t i n g
c o n t r o l c h a r a c t e r i s t i c wae d e t e r m i n e d t o b e do m n d e n t upon
f r e q u e n c y o f a >- I i e d anode v o l t a g e , I n t e r e l e c t r o d e c a p a c i ­
t a n c e , and t u b e " d a r k " c u r r e n t s which a r e d e t e r m i n e d by
geometry o f e l e c t r o d e s t r u c t u r e s .
x t l n g ilsh ln g co n tro l
c h a r a c t e r i s t i c was found t o b e a t u b e d e i o n i z a t i o n
phenomenon
_
4 -
VARIATION OF CONTROL OHA ACTStIOTICO OF
POAER THYXATRON TUBOS HTH FREQUENCY
INTRODUCTION
The i n d u s t r i a l a p p l i c a t i o n o f e l e c t r i c
X>wer a t
f r e q u e n c i e s o t h e r t h a n t h o s e n o r m a l l y employed f o r g e n e r a t i o n
la in creasin g rao ld ly ,
e s p e c i a l l y f o r such s p e c i a l i s e d
purposes as h e a tin g , b ra z in g ,
by i n d u c t i o n ,
s o l d e r i n g and m e l t i n g o f m e t a l s
sp e ed c o n t r o l o f m o t o r s b y f r e q u e n c y v a r i a t i o n ,
s e r v o - m e c h a n i s m c o n t r o l s , r a d a r m o d u l a t o r s , and a i r c r a f t
r e c t i f i e r s and I n v e r t e r s .
Power a t t h e d e s i r e d
frequency
o f u t i l i z a t i o n i s g e n e r a l l y o b t a i n e d from s t a n d a r d f r e q u e n c y
power s y s t e m s b y means o f f r e q u e n c y c o n v e r t i n g d e v i c e s o r
g e n e r a t i n g d e v i c e s w h ic h a r e more and more t a k i n g t h e form
of c ir c u its in corporating th y ratro n tubes.
G e n e ra lly the
c i r c u i t s used i n t h e s e freq u e n cy c o n v e r t in g o r g e n e r a t i n g
dev ices a re w ell understood, b u t u n t i l r e c e n tly th e v a ria ­
t i o n s which might o c c u r i n t h e c o n t r o l c h a r a c t e r i s t i c s o f
t h e t h y m t r o n t u b e s when s u b j e c t e d t o h i g h e r - t h a n - p o w e r
f r e q u e n c i e s were n o t known, t h o u g h i t was and i a g e n e r a l l y
a c c e p t e d t h a t t h e r e a r e f r e q u e n c y l i m i t a t i o n s i n t h e use o f
t h e s e t u b e s b e c a u s e o f f i n i t e i o n i z a t i o n and d e i o n i z a t i o n
tim es
- 5 HISTORICAL SUHVZY
Aa e a r l y a s 1934 B e r k e y and H a l l e r p o i n t e d o u t t h a t
t h y r a t r o n f i r i n g c h a r a c t e r i s t i c s would depend o n f r e q u e n c y
I
o f applied v o lta g e .
I t was I n d i c a t e d by v.. 9 . Sh e p h e rd
I n 1943 t h a t t h e r e were two c o n t r o l c h a r a c t e r i s t i c s I n
t h y r a t r o n c o n t r o l phenomena w h i c h h e c l a s s e d a s s t a t i c and
2
dyn amic c h a r a c t e r i s t i c s .
H. H. W i t t e n b e r g
i n 1945 I n t r o ­
du ced t h e c o n c e p t o f a s t a r t i n g c o n t r o l c h a r a c t e r i s t i c ,
m eanin g f i r s t c y c l e s t a r t i n g a s compared t o s u c c e s s i v e c y c l e
f i r i n g , and an e x t i n g u i s h i n g c o n t r o l c h a r a c t e r i s t i c , meaning
f a i l u r e t o I g n i t e on s u c c e s s i v e c y c l e s , and showed t h a t
t h o u g h t h e s e c h a r a c t e r i s t i c s a r e g e n e r a l l y c o i n c i d e n t a t low
f r e q u e n c i e s (60 c y c l e s p e r s e c o n d ) t h e y may become s e p a r a t e ,
a t l e a s t f o r the c o n tr o l type t h y r a tr o n tu b e s .
range o f f r e q u e n c ie s .
As t h e f r e q u e n c y i s
co n tro l c h a r a c te r is tic s ex h ib it s h if ts ,
In the
increased both
the ex tin g u ish in g
c h a r a c t e r i s t i c g e n e r a l l y s h i f t i n g most.
I t was u o i n t e d o u t
t h a t t h e s t a r t i n g c h a r a c t e r i s t i c would t e n d t o s h i f t I n a
n e g a tiv e d i r e c t i o n b e ca u se o f c o u p lin g to the g r i d through
t h e a n o d e - g r i d c a p a c i t a n c e and a l s o b e c a u s e o f i n c r e a s e d g a s
p r e s s u r e , w h i l e t h e e x t i n g u i s h i n g c h a r a c t e r i s t i c would a l s o
tend to s h i f t n e g a tiv e ly w ith In c re a s e In g rid r e s i s t a n c e ,
i n c r e a s e o f an o d e c u r r e n t ,
in c re a s e i n gas p re s s u re , the
p r e s e n c e o f a nd t h e amount o f I n d u c t a n c e i n t h e
c irc u it,
as w ell as in c r e a s in g frequency.
an o d e
I t was a l s o noted.
mm
(>
t h a t t h e s h i f t was more n o t i c e a b l e I n t h o s e t u b e s w i t h
l a r g e r c r o s s - s e c t i o n a l e l e c t r o d e a r e a Vor g r e a t e r v o l u m e ) .
I t waa t b e p u r p o s e o f t h i s I n v e s t i g a t i o n t o s t u d y t h e
v a r i a ti o n In the c o n tro l c h a r a c t e r i s t i c s of the la r g e r
power t h y r a t r o n t u b e s o f t h e s i n g l e g r i d , m e r c u r y - v a p o r
ty p e b ecau se of t h e t r e n d tow ard I n s t a l l a t i o n s r e q u i r i n g
more power t h a n c o n t r o l t y p e t h y r a t r o n t u b e s c a n s u p p l y .
One t h y r a t r o n t u b e o f t h e M e rc u r y - v a p o r - 1 n e r t - g a s s t a b i l ­
i z e d t y p e was a l s o t e s t e d .
Tubes t e s t e d
FG-57 , FG-6 7 , 3C23, 9 6 7 , UX9 7 3 .
v e rs SG-2 7 A,
- 7 DESCRIPTION OF TZGT Z Q , U I N T AND =XOCZDU .S
F i g u r e I Bhoxs a d i a g r a m o f t h e c i r c u i t u s e d f o r t e s t ­
ing the tubes.
The t a p s on t h e i n v e r t e r p r o v i d e d a d j u s t a b l e
an o d e v o l t a g e f o r t h e t u b e u n d e r t e s t up t o
850 v o l t e #
ooak v a l u e s o f
Rj was a v a r i a b l e r e s i s t o r i n t h e a n o d e l e a d t o
l i m i t t h e a v e r a g e anode C u r r e n t .
F i l a m e n t power was
sup­
p l i e d from 1 60 C y c l e p e r se co nd a m r o e t h r o u g h a v a r i a c i n
o r d e r t o k e ep t h e f i l a m e n t v o l t a g e c o n s t a n t a s w e l l a s t o
p r o v i d e roite m e a s u r e o f c o n t r o l o f t h e c o n d e n s e d m e r c u r y
te m p e r a tu re o f tlie tu b e under t e s t .
A s m a l l a i r b l o w e r was
a l s o used i n t h i s c o n n e c t i o n .
A s i n e wave o f t e s t v o l t a g e wgta u se d b e c a u s e wave s h a p e
d o e s a f f e c t t h y r a t r o n p e r f o r m a n c e , and t h e s i n e , wave n o t o n l y
g i v e s r e s u l t s e a s i e r t o a n a l y z e b u t i s a l s o most w i d e l y u s e d
o f a l l wave s h a p e s .
V o l t a g e wave s h a p e was m o n i t o r e d by t h e
c a t h o d e r a y o s c i l l o s c o p e and c h e c k e d by c o m p a r i s o n o f t h e
r e a d i n g s o f a r e c t i f i e r t y p e v o l t m e t e r and a r a d i a l v ane t y p e
v o ltm eter.
F r e c u e n c y o f t h e a p p l i e d v o l t a g e was d e t e r m i n e d
b y means o f t h e a u d i o f r e q u e n c y o s c i l l a t o r and t h e L i s s a j o u s
p a t t e r n on t h e s c r e e n o f t h e c a t h o d e r a y o s c i l l o s c o p e .
Grid
v o l t a g e was o b t a i n e d from a 2 A v o l t b a t t e r y and t h e p o t e n t ­
iom eter.
The t u b e u n d e r g o i n g t e s t was f i r e d a t t h e c r e s t o f
t h e a n o d e s u p p l y v o l t a g e wave b y m a g n i t u d e c o n t r o l o f t h e
g r i d v o l t a g e and t h e f i r i n g
?o in t was m o n i t o r e d w i t h t h e
_ 8 -
cathode ray o s c lllo a c o o e .
The s o u r c e o f t h e t e s t v o l t a g e was a p a r a l l e l I n v e r t e r
u s i n g s p a i r o f P1'^ 6 7 t h y r a t r o n t u b e s .
Output
power was
l i m i t e d by t h e i n p u t v o l t a g e r a t i n g o f t h e i n v e r t e r t r a n s ­
former
and t h e c u r r e n t r a t i n g o f t h e I n v e r t e r t u b e s .
i n v e r t e r was c h o s e n a s b e i n g b e s t a b l e t o s u n l y t h e
The
re­
q u i r e d v a r i a b l e f r e q u e n c y , v a r i a b l e v o l t a g e power s o u r c e o f
good o u t p u t wave s h a p e .
O t h e r means o f o b t a i n i n g v a r i a b l e
3 , 4, 5,
f r e q u e n c y , v a r i a b l e v o l t a g e power were s t u d i e d
but
r e j e c t e d as b e in g too c o s t l y o r o f i n s u f f i c i e n t frequency
range.
- 9 TEST RESULTS
STAixTl MO- CHARACTERIGTICS
I t was a ,Dparent a s t e s t i n g a d v a n c e d t h a t t h e two c o n ­
t r o l c h a r a c t e r i s t i c s fo und f o r t h e s m a l l e r t u b e s would
g e n e r a l l y b e found f o r t h e l a r g e r t u b e s a l s o .
The s t a r t i n g
c h a r a c t e r i s t i c s would i n g e n e r a l s h i f t w i t h t h e f r e q u e n c y
o f t h e a p p l i e d anode v o l t a g e as can be r e a d i l y aoen i n
f i g u r e s 2 , 3 , and 4 , t h o u g h t h e d e g r e e o f s h i f t m i g h t b e so
s l i g h t a s t o b e masked by e x p e r i m e n t a l i n a c c u r a c i e s a s e v i ­
d e n ce d by f i g u r e s 5 , 6 , and 7 en d a l s o b y t h e c u r v e o f
f i g u r e 4 t a k e n a t 769 0 . c o n d e n s e d m e r c u r y t e m p e r a t u r e .
F i g u r e 3 sh o w in g t h e s h i f t o f s t a r t i n g c h a r a c t e r i s t i c
w i t h f r e q u e n c y i n t h e t y p e 7*3» 6 7 t h y r a t r o n t u b e was o f
especial In te re s t,
s i n c e t h e s h i f t h e r e I s shown i n a pos­
i t i v e d i r e c t i o n where a l l o t h e r t u b e s e x h i b i t e d , where
n o tic e a b le , a s h i f t in the negative d ir e c tio n .
W ittenberg,
a s was n o t e d p r e v i o u s l y , i n d i c a t e d t h a t t h e n e g a t i v e s h i f t
could l a r g e l y be accounted
for by tb e v o lta g e induced In to
th e g r id c i r c ; i t through th e a n o d e-g rid c a p a c ita n c e w ith
other facto rs
s u c h a s d - c l e a k a g e c u r r e n t s and g r i d e m i s s i o n
also c o n trib u tin g .
C o n sid e ratio n o f the e q u iv a le n t c i r c u i t
for a single
g r i d t h y r a t r o n t u b e I n h a l f wave r e c t i f i e r s e r v i c e w i t h a
r e s is ta n c e load,
so u rc e lmoedance n e g l i g i b l e , l e a d s to t h e
-
10 -
f o llo w in g e x p r e s s io n f o r t h e v o l ta g e Induced I n t o t h e g r i d
c i r c u i t through th e tube i n t e r e l e c t r o d e c a p a cita n c es in ­
c l u d i n g t u b e b a s e and s o c k e t ;
( See a p p e n d i x I .)
(I)
TM s e q u a t io n I s , o f c o u r s e , v a l i d o n ly d u r i n g non-conduc­
tio n .
F i g u r e 3 shows a n o d e - g r i d cou l i n g i n a t h y r a t r o n
tu b e ( e x ag g e ra ted f o r purposes o f I l l u s t r a t i o n )
a t e d by e q u a t i o n I .
as calcul­
I t c a n b e s e e n from f i g u r e 8 t h a t t h e
e f f e c t o f t h e v o l t a g e Induced i n t o t h e g r i d c i r c u i t by th e
a n o d e - g r i d c a p a c i t a n c e c o u p l i n g i s t o r e q u i r e more n e g a t i v e
d -c g r i d b i a s to p rev e n t f i r i n g , though t h e n e c e ssa ry i n ­
c re a s e in b i a s v o lta g e w i l l be l e s s th an th e c r e s t value of
th e induced v o l t a g e .
A lso, th e induced v o lta g e w i l l tend
t o f i r e t h e t u b e somewhat b e f o r e c r e s t an o d e v o l t a g e I s
reached.
Eecauae o f th e unusual b e h a v io r o f the s t a r t i n g
c h a r a c t e r i s t i c o f t h e t y p e FQ- 6 7 t
=M r o n , p e a k v a l u e s o f
i n d u c e d g r i d v o l t a g e s were c a l c u l a t e d b y means o f e q u a t i o n I
f o r a l l t u b e s u s e d i n t h i s s t u d y and a l s o f o r t h o s e t u b e s
u s e d i n t h e W i t t e n b e r g s t u d y and p l o t s were made t o d e t e r m i n e
t h e amount o f s h i f t I n s t a r t i n g c o n t r o l c h a r a c t e r i s t i c w h i c h
would be c a u s e d i n e a c h c a s e .
The r e s u l t s o f t h i s work a r e
shown i n t a b l e $ i n c o m p a r i s o n w i t h t h e s h i f t i n s t a r t i n g
—
■ IX —
c o n tro l c h a r a c t e r i s t i c a c tu a lly observed.
Table I a ls o l i s t s
th e a n o d e-g rid c a p a c ita n c e s Includ­
i n g t u b e b a s e and s o c k e t as m e a s u r e d f o r t h o s e t u b e s t e s t e d
I n t h i s s t u d y and a l s o t h o s e v a l u e s l i s t e d by W i t t e n b e r g I n
h is study.
I t w i l l be noted t h a t th e measured v a l u e s a r e
a l l g r e a t e r th a n th e f i g u r e s p u b lis h e d by tu b e m a n u f a c tu r e r s .
T h i s i s b e c a u s e o f t h e added c a p a c i t a n c e from t h e t u b e b a s e
and s o c k e t s .
E xam ination o f t a b l e I d i s c l o s e s t h a t o f t h e eleven
t u b e s t e s t e d t h e s t a r t i n g c o n t r o l c h a r a c t e r i s t i c o f one
tube s h ifte d in a p o s itiv e d ir e c tio n .
For f o u r t u b e s no
s h i f t I n s t a r t i n g c o n t r o l c h a r a c t e r i s t i c was o b s e r v e d ,
though t h i s i s not c o n clu siv e s in c e th e s h i f t p re d ic te d f o r
two o f t h e t u b e s b y c o n s i d e r a t i o n o f a n o d e - g r i d c o u p l i n g l a
so s l i g h t a s t o b e masked by e x p e r i m e n t a l e r r o r an d i n t h e
c a s e o f t h e o t h e r two t u b e s t h e p r e d i c t e d s h i f t i s z e r o .
F o r t h e r e m a i n i n g s i x t u b e s t h e o b s e r v e d s ■I f t
in s to u tin g
c o n tro l c h a r a c t e r i s t i c la s u b s ta n tia lly g r e a te r th an th a t
p r e d i c t e d from c o n s i d e r a t i o n o f a n o d e - g r i d c o u p l i n g .
In
th o s e I n s ta n c e s o f n e g a tiv e s h i f t In s ta rtin g , c o n t r o l char­
a c t e r i s t i c g r e a t e r t h a n p r e d i c t e d by a n o d e -g rid c o u p lin g a
p a r t o f t h e ad d ed s h i f t may b e c a u s e d by d - c l e a k a g e
c u r r e n t s o v e r t h e stem p r e s s b e t w e e n t h e c a t h o d e a nd g r i d
TABLE I
COMPARISON OF CALCULATED* AND OBSERVED SHIFT OF STARTING CONTROL
Tube
T ype
A n od e-G rid
C a p a c ita n c e
Mmfd
0 .2 5
2D21 **-*
3D22 * ■ 0 . 4 5
0 .5 0
2050
0 .6 0
2051
6 .4 0
884
1 1 .0
FG-27A
1 1 .0
P G -57
1 2 .0
F G -67
1 0 .0
3023
1 6 .0
967
1 3 .0
UX973
G rid
R e s is t­
ance
Ohms
0 . 1 meg
H
!T
IT
Tl
5000
2000
5000
5000
5000
6000
F requ en cy
3500
3500
1500
3500
700
1020
920
1280
1020
1020
1020
C rest
Anode
V o lts
650
650
1000
650
300
800
650
800
SOO
850
900
Crest
In d u ce d
G rid V o l t s
0 .0 5 1
0 .6 4 3
0 .5 7 0
0 .7 9 1
0 .4 3
0 .2 7 7
0 .0 8 9 7
0 .5 0 2
0 .2 6 5
0 .4 2 6
0 .3 4 7
C a lc u la t e d
S h ift
V o lts
0 .0 0
xtm mo ^
mm
0 .0 0
-1 .6 0
0 .0 0
0 .0 0
-0 .0 5
- 0 .0 5
- 0 .0 5
-0 .0 5
-f'"+■
CHARACTERISTICS
M easured
S h ift
D iffe r e n c e
Volts
0 .0 0
-0 .2 0
-0 .9 0
-1 .7 0
—1 . 0
0 .0 0
- 0 .3 5
+ .Lu
—0 * 2 0
0 .0 0
0 .0 0
0 .0 0
——
—— -2 .4 0
-0 .3 5
+ i .6 0
-0 ,2 1 5
0 .0 5
0 .0 5
* Caloulated values were computed from equation I and accurate p lo ts of ap p lied anode volt. ,
induced v o lt s , and c r i t i c a l grid v o lta g e s.
** Shield grid type t Hvratrons. A ll others are sin g le grid type thyratrons*
*** Could not be accurately p lo tte d .
Note: 2D21, 3D22, ‘2050, 2051, 884, data from W ittenberg’s a r t i c l e .
stu d y .
A ll other data from present
-
stru ctu res,
13 -
a n d , I n t u b e s w h ic h h a v e b e e n i n u s e l o n g
eno ugh f o r c a t h o d e c o a t i n g t o h ave b e e n d e p o s i t e d on t h e
g r i d s t r u c t u r e , g r i d e n l a i o n may a c c o u n t f o r a p a r t o f
t h e ad d ed s h i f t .
I n t h e c a s e o f t h e t y p e FO- 6 7 t h y r n t r o n
t u b e none o f t h e f o r e g o i n g s e r v e s t o e x p l a i n t h e o b s e r v e d
oosltive s h if t in s ta r tin g control c h a r a c te r is tic .
I t l a suggested t h a t the o o s ltiv e shift, in th e s t a r t ­
i n g c h a r a c t e r i s t i c o f t h e FGw6? t h y r & t r o n may b e c a u s e d by
4 ,6 ,7 ,
r e l a t i v e l y la r g e "dark" c u r r e n ts
In the grid c irc u it
ju s t p rio r to f i r in g ,
'’D a r k " c u r r e n t , t h e r e s u l t o f e l e c ­
tr o n s le a v in g th e cathode w ith s u f f i c i e n t therm al a c c e le r ­
a tio n to reach th e g rid ,
tem perature, g rid
i s norm ally a f u n c t i o n o f cathode
p o t e n t i a l , and an o d e p o t e n t i a l ,
be alm ost co m p letely zero a t high n e g a tiv e g r id
w i t h low an o d e v o l t a g e .
It
and may
-otentlale
l a i n t e r e s t i n g t o n o t e from
f i g u r e 8 t h a t th e e f f e c t o f t h e Induced g r id v o l t a g e i s t o
n u l l i f y t h e e f f e c t o f t h e n e g a t i v e g r i d b i a s v o l t a g e so
t h a t t h e " d a r k ” c u r r e n t i n c r e a s e s i n m a g n i t u d e aa t h e
a p p l i e d an o d e v o l t a g e b e g i n s t o i n c r e a s e p o s i t i v e l y and
add i t s
e f f e c t to t h a t o f th e induced g r i d v o l t a g e to fu r­
t h e r i n c r e a s e t h e m agnitude o f th e "d a rk ” c u r r e n t ,
Since
t h e d i r e c t i o n o f flow o f t h i s
" d a r k " c u r r e n t I a from g r i d
to cathode, a v o lta g e drop i s
produced i n t h e e x t e r n a l g r i d
r e s i s t a n c e o f s u c h P o l a r i t y a s t o p r e v e n t t h e t u b e from
14 _
firin g .
There I
foregoing.
b
some e x p e r i m e n t a l e v i d e n c e I n s u p p o r t o f t h e
A t t e m p t s were made t o m e a s u r e t h e m a g n i t u d e o f
t h e g r i d c u r r e n t i n t h e PCJ-6? j u s t p r i o r t o f i r i n g *
d i f f i c u l t task*
a rather
s i n c e t h e l a r g e v a l u e o f g r i d c u r r e n t flo w ­
i n g a f t e r f i r i n g may damage t h e i n s t r u m e n t used f o r m ea su re ­
ment o f t h e '‘d a r k " c u r r e n t .
I t was d e t e r m i n e d t h a t when a
v o l t a g e w i t h a f r e q u e n c y o f 550 c y c l e s p e r s e c o n d and c r e s t
v a l u e o f 560 v o l t s was a p p l i e d t o t h e anod e c i r c u i t o f t h e :
tube the average d-c g rid c u rr e n t, t h a t i s ,
"dark
p r i o r t o f i r i n g was a t l e a s t 12 m i c r o am p e r e a .
current,
T h i s i s prob ­
a b l y w e l l b e lo w t h e a c t u a l v a l u e o f a v e r a g e g r i d c u r r e n t
flow ing a t
]u st the I n s ta n t b e fo re f i r in g because consider­
a b l e c a u t i o n was e x e r c i s e d f o r p r o t e c t i o n o f t h e d - c
m ic r o a m m e t e r used t o m e a s u r e t h e g r i d c u r r e n t .
A lso , t h e
m ic r o a m m e t e r d i d n o t m e a s u r e p eak v a l u e s o f any p u l s a t i o n s
which m ight b e p r e s e n t .
" D a rk " c u r r e n t s a r e p a r t i c u l a r l y n o t i c e a b l e i n t h e
g r i d c i r c u i t s o f t h o s e t h y r a t r o n t u b e s where t h e g r i d b a f f l e
I s e f f e c t i v e l y in te rp o s e d in th e path of th e a rc -s tre a m .
c a n b e s e e n fro m f i g u r e 12 t h a t t h e t y p e
T i-6 7 t h y r a t r o n I s
o f su ch c o n s t r u c t i o n a s t o b e i n t h i s c l a s s .
and t y p e UX973 a l s o a r e i n t h i s
b a f f l e s do n o t l i e
It
The t y p e 96T
c l a s s , though h e re th e g r i d
so c o m p l e t e l y I n t h e p a t h o f t h e a r c -
-
stream .
15 -
I n t h e c a s e o f t h e s e l a s t two t y oa no s h i f t I n
s t a r t i n g c h a r a c t e r i s t i c c o u l d be o b s e r v e d e x p e r i m e n t a l I y ,
t h o u g h a s l i g h t s h i f t was p r e d i c t e d b y c o n s i d e r a t i o n o f
anode-grid coupling.
types the g rid
I t seems p r o b a b l e t h a t I n t h e s e
' d a r k " c u r r e n t was o f s u f f i c i e n t m a g n i t u d e
t o j u s t c o u n t e r a c t t h e n e g a t i v e s h i f t caused by a n o d e - g r id
c o u p l i n g and o t h e r e f f e c t s .
I n t h e case o f such t h y r a t r o n tu b e ty p e s as th e
13- 5 7 ,
f i g u r e 12 shows t h a t t h e h o l e i n t h e g r i d b a f f l e I s a s l a r g e
os t h e c a t h o d e e m l e a l d t i h o l e and so t h e g r i d c a n n o t b e s a i d
t o be
1I n t e r p o s e d " I n t h e p a t h o f t h e a r c - s t r e a m .
be ex p ected t h a t g r i d
I t would
" d a r k * c u r r e n t i n t h i s c a s e would b e
s m a l l i n m a g n i t u d e and o f n e g l i g i b l e I m p o r t a n c e a s f a r as
a ffe c t of the s ta r tin g control c h a r a c te r is tic i s
concerned
and s u c h i s a c t u a l l y t h e c a s e , no m e a s u r e a b l e g r i d " d a r k "
c u r r e n t s b e i n g fo u n d f o r t h i s t u b e .
A t t e m p t s were made t o m e a s u r e l e a k a g e c u r r e n t s and
l e a k a g e r e s i s t a n c e v a l u e s i n t h e t u b e s u n d e r t e s t w i t h como le te ly negative r e s u l t s .
i s a n e x am p le ; t h e t . pe FG-57
t h y r a t r o n would r e q u i r e a c a t h o d e - g r i d l e a k a g e c u r r e n t o f
175 microam s e r e s t o a c c o u n t f o r t h e d i f f e r e n c e b e t w e e n t h e
o b s e r v e d and p r e d i c t e d s h i f t i n s t a r t i n g c o n t r o l c h a r a c t e r ­
istic s.
'io m e a s u r e a b l e l e a k a g e c u r r e n t s were fo u n d w i t h
i
-
16 -
n e g a t i v e g r i d v o l t a g e s a e g r e a t a s 24 v o l t s .
>rom t h i s i t
may b e c o n c l u d e t h a t t h e e f f e c t o f l e a k a g e c u r r e n t s i n
s h i f t i n g the s t a r t i n g
control c h a r a c te r is tic negatively is
a s etmall o r s m a l l e r t h a n t h e d i r e c t e f f e c t o f g r i d v o l t a g e
Induced through a n o d e - g r id c o u p lin g .
The f o l l o w i n g t h e o r y I e o f f e r e d i n e x p l a n a t i o n o f t h e
s h i f t i n s t a r t i n g c o n t r o l c h a r a c t e r i s t i c s o f t h r e e element
t b y r a t r on t u b e s :
I n any h o t c a t h o d e t u b e a c e r t a i n number o f e l e c t r o n s
le a v e th e cathode w ith s u f f i c i e n t therm al a c c e l e r a t i o n to
r e a c h e i t h e r t h e g r i d b a f f l e o r t h e g r i d - a n o d e s >ace u n l e s s
t h e g r i d I s made s u f f i c i e n t l y n e g a t i v e r e l a t i v e t o t h e c a t h ­
od e t o r e p e l a l l t h e s e h i g h s p e e d e l e c t r o n s .
T h o se e l e c t r o n s
r e a c h i n g t h e g r i d b a f f l e s u r f a c e f i n d t h e i r way b a c k t o t h e
c a t h o d e by way o f t h e g r i d c i r c u i t and p r o d u c e t h e g r i d
"dark'
c u rr e n t p re v io u s ly m entioned.
Tho se e l e c t r o n s which
p a ae t h r o u g h t h e g r i d h o l e s and r e a c h bho g r i d - a n o d e s p a c e
p r o d u c e i o n i z a t i o n i n t h i s r e g i o n when t h e an o d e i s a t a
p o sitiv e p o te n tia l.
The p o s i t i v e i o n s p ro d u c e d I n t h e g r i d -
anode s p a c e a r e a t t r a c t e d
t o t h e g r i d and s t a r t f o r m i n g a
p o s i t i v e space c h a rg e n e a r t h e g r i d which te n d s t o n u l l i f y
t h e e f f e c t o f t h e n e g a t i v e g r i d b i a s and so p e r m i t more
e l e c t r o n s to e n t e r th e g rid -a n o d e r e g io n to produce g r e a t e r
io n izatio n .
U n l e s s t h e g r i d l a made s u f f i c i e n t l y more
17 -
n e g a tiv e to r e p e l a l l e le c t r o n s tho tube w i l l i g n i t e .
As t h e f r e q u e n c y o f t h e a p p l i e d anode v o l t a g e i s i n ­
c re a s e d t h e m agnitude o f th e v o l t a g e induced I n t h e g r i d
c i r c u i t b y a n o d e - g r i d c o u p l i n g b ecom es a p p r e c i a b l y l a r g e .
I t was p o i n t e d o u t p r e v i o u s l y - t h a t t h i s i n d u c e d v o l t a g e
cannot o f i t s e l f produce a l l th e observed s h i f t I n s t a r t i n g
control c h a r a c te r is tic .
It is
so p h a s e d , h o w e v e r , a s t o h e
p a r t i c u l a r l y e f f e c t i v e in reducing th e e f f e c t o f th e n egative
grid b ia s v oltage.
T his w i l l cause th e s t a r t i n g c o n tr o l
c h a r a c t e r i s t i c to s h i f t stro n g ly in a negative d i r e c tio n in
th o se n e g a tiv e - g r id t h y r a t r o n tu b es w ith a s in g le la rg e
o o e n l n g i n t h e g r i d b a f f l e b e c a u s e t h e weakened g r i d f i e l d
w i l l perm it i o n iz i n g e le c t r o n s to pass through th e la rg e
h o l e i n t h e g r i d b a f f l e and r e a c h t h e g r i d - a n o d e a p a ce .
In
t h o s e n e g a t i v e - g r i d t h y r a t r o n t u b e s w i t h a medium s i z e h o l e
i n t h e g r i d b a f f l e some e l e c t r o n s may p a s s t h r o u g h t h e h o l e
and o t h e r s s t r i k e t h e b a f f l e r e s u l t i n g i n some i o n i z a t i o n
I n t h e a n o d © „ g r i d r e g i o n and a t t h e same t i m e , some " d a r k *
c u rre n t in the g rid c i r c u i t .
s li g h t neg ativ e s h i f t ,
The n e t r e s u l t may b e a
no s h i f t , o r a s l i g h t p o s i t i v e s h i f t
i n t h e s t a r t i n g c o n t r o l c h a r a c t e r i s t i c dep en d in g upon th e
s iz e o f the hole i n the g rid b a f f l e .
In tho se negative-
g r i d t h y r a t r o n tu b e s c o n s tr u c te d l i k e th e Ff-L7 w ith a g r id
b a f f l e c o n s i s t i n g o f a d i s k w i t h many s m a l l h o l e s t h e weak-
18 -
enlng of t h e g r i d
f i e l d by t h e i n d u c e d g r i d v o l t a g e w i l l
CAtme t h e >:?rld " d a r k " c u r r e n t t o I n c r e a s e and so si I f t t h e
s t a r t s tv c o n tr o l c h a r a c t e r i s t i c In a ooultlve
The s t a r t i ng co -I'.rol c h a r a c t e r i s t i c o f a l l
‘V - c t L
n a lt l v c - r rid
t h y r r t - on t u b e s s h o u l d s h i f t i n t h e p o s i t i v e d i r e c t i o n s
A c c o r d i n g t o t h e above t h e o r y an l n c n c a c e i n f r e q u e n c y
should cau se t h e s t a r t i n g c o n t r o l c h a r a c t e r i s t i c o f the
n e g a tiv e -g rid th y n a tro n tubes w ith s in g le la rg e hole In th e
g r i d b a f f l e t > SM f t more ac
L ively,
ho s i b' v e - g r l d t h y -
r a t r o n t u b e s and t h o s e n e g a t i v e - g r i d t h y r a t r o n t u b e s w i t h
g r i d b a f f l e s made a s a d i s k w i t h many s m a l l h o l e s w i l l
e x h ib it a s h i f t of the s t a r t i n g C ontrol o h o ro o terI s t i c In
the
x> eltive d i r e c t i o n .
The s h i f t o f s t a r t i n g c o n t r o l
c h a r a c t e r i s t i c of t h r e e n e g a tiv e - g r id tb y r a t r o n tube? with
r
.od.uratf. s i z e . U n g l e b o l e I u t h e g r i d be:' I e
d e terv in F te.
In cre ase of grid re s is ta n c e
i l l be in -
should produce th e
aamc e f f e c t a s l n c r e r e e o f f r e q u e n c y .
D a t a was t a k e n f o r e a c h t u b e a t t w o d i f f e r e n t v a l u e s o f
c o n d en se d m e r c u r y t e ' e r a b u r e i n o r d e r t o d e t e r
" ne t h e e f f ­
e c t o f t e m p e r a t u r e on s t a r t i n g c o n t r o l c h a r a c t e r i s t i c s h i f t .
I t was e x p e c t e d t h a t a t h i g h e r t e m p e r a t u r e t h e s h i f t would
b e - o r e n e g a t i v e , s i n c e i n c r e a s e d tern e r s t u r c e f f e c t i v e l y
I vc
•
_:
gaa
- sure.
s u r e would be a b o u t $$ ( S e e
Xctuall
f e lncueas
Xppendix I I ) w h i c h
pres­
>robably would
19 -
not. n o t i c e a b l y a f f e c t r e s u l t s .
There I e some s l i g h t ex­
p e r im e n ta l e v id e n c e t h a t th e s h i f t a t t h e h ig h e r v a l u e s o f
condensed mercury tem p er a tu r e i s l o s s th a n a t th e lower
v a l u e s o f condensed mercury te m p e r a tu r e , b u t t h i s v a r i a t i o n
In s h i f t I
b
So
v e r y s l i g h t t h a t i t can b e charged to e x p e r i­
m en tal e r r o r and so sh o u ld n o t b e c o n s id e r e d as b e i n g i n any
manner c o n c lu s i v e *
T h is was e s p e c i a l l y t r u e i n t h e c a se o f
3-C23 which i s t h e m ercury-vapor i n e r t - g a s - s t a b i l i z e d tu b e ,
'ere th e e x p e r im e n t a l d e t e r m i n a t i o n o f t h e s t a r t i n g char­
a c t e r i s t i c a t th e h ig h e r v a lu e o f condensed mercury
te m p e r a tu r e became q u i t e d i f f i c u l t ,
any a l i g h t change i n
f i l a m e n t v o l t a g e b e i n g i n s t a n t l y r e f l e c t e d i n a change o f
e m i s s i o n and so o f s t a r t i n g c h a r a c t e r i s t i c *
I n d e e d , at
condensed mercury t e m p e r a tu r e s o f 3 0 ° C* and above th e
s t a r t i n g c o n t r o l c h a r a c t e r i s t i c becom es so e r r a t i c as to
be c l a s s e d a s a random phenomena.
— 20 —
EXT I iHUISHI Ml CHARACTERISTICS
• I t ',vaa. u n f o r t u n a t e t h a t t h e e x t i n g u i s h i n g c h a r a c t e r .
I a t • co c o 'i Id iAt ca f u l I j I n v a 1 1 i g a t e d , b ut powe r I i m i t a t i o n a and t h e I n h e r e n t u n b a l a n c e d l o a d
I n v e r t e r by t h e t e s t
oreeented to the
c i r c u i t nade complete e x p e rim e n ta l
study o f th e e x tin g u is h in g c h a r a c t e r i s t i c Im p o ssib le.
At power f r e q u e n c i e s o f 60 c y c l e s per second th e
g r id can c o n t r o l t h e a v e r a g e anode c u r r e n t b y c o n t r o l l i n g
th e p o in t on the p o s i t i v e v o l t a g e wave a t which t o e tube
fir e s.
T h is f e a t u r e i s l o s t a t a u d io f r e q u e n c i e s , f o r
h e r e t h e r e s i d u a l I o n i z a t i o n i s such t h a t th e g r i d can
p r o v id e o n ly o n - o f f c o n t r o l o f t h e anode c u r r e n t , a t l e a s t
when o n ly m agnitude d -o c o n t r o l I s used on t h e g r i d s .
T ests -iVere made up t o t h e l i m i t o f th e t e s t equipment
w hich i n g e n e r a l seemed t o i n d i c a t e a ne a l i v e s h i f t o f t h e
e x tin g u ish in g c h a r a c t e r is t ic .
The a v e r a g e anode cu rren t o f
t h e s e t e s t a was o n ly 0 , 1 amperes comoared t o t h e r a te d aver­
age anode am >erea o f from 1 . 2 5 amperes to 2 . 5 amperes and so
t h e s e r e s u l t s can show l i t t l e more th a n a t r e n d .
F ig u re 9
shows th e measured s h i f t i n e x t i n g u i s h i n g c h a r a c t e r i s t i c a t
1000 c y c l e s per second f r e e .iency a p o l i e d anode v o l t s for 0 . 1
ampere a v e r a g e anode c u r r e n t , r e s i s t a n c e l o a d , f o r th e t y r e
TC-5 7 .
F ig u r e 10 shows th e measured s h i f t i n e x t i n g u i s h i n g
c h a r a c t e r i s t i c f o r t h e 3023 a t 0 . 1 a v e r a g e anodo am peres.
21 _
r e s i s t a n c e I o p g !.
I n t h e c a s e o f t h e P Q - 5 ? o n ly 4 ' o f
r a t e d a v e r a g e anode c u r r e n t i s b e in g passed and y e t the
e x t i n g u i s h i n g c o n t r o l c h a r a c t e r i s t i c has s h i f t e d nogat l v e l y by 1 0 . 9 v o l t s a t 603 peak anode v o l t s .
?art of
t h i s s h i f t may b e cau sed by t h e in d u c ta n c e o f th e In­
v e r t e r tr a n s f o r m e r w h ich , by p r o lo n g in g anode c u r r e n t
flo w i n t o th e tim e o f n e g a t i v e anode v o l t a g e , d e c r e a s e s
t h e tim e a v a i l a b l e f o r tu b e d e i o n i z a t i o n .
V itte n b e r g has found t h a t a l i n e a r r e l a t i o n s h i p
e x i s t s b e tw e en a v e r a g e anode amperes and g r id v o l t a g e
r e q u ir e d t o e x t i n g u i s h a g i v e n tub a a t a g i v e n fre q u en cy
and peak anode v o l t a g e .
E xp ressed a s an e q u a t io n t h i s
would be
= - ( K 1I -h
2)
(2)
where K-, would b e a c o n s t a n t d e p e n d in g upon e l e c t r o d e
g e o m e tr y , fr e q u e n c y o f a p p l ie d r iode v o l t a g e , and g a s
p r e s s u r e , and K_ would be t h e g r id v o l t a g e i n t e r c e p t .
?
I t has b e e n shown
6
t h a t under s t a t i c c o n d i t i o n s tu b e
d e i o n i z a t i o n tim e may be c a l c u l a t e d
from t h e e m p i r i c a l
r e la tio n
t = O.. QOlgpI0 *?
3 /2
eg
x
where p i s
(3)
th e g a s p r e s s u r e In dynea per square c e n t i m e t e r ,
I i s th e arc c u r r e n t , x i s th e d i s t a n c e b etw een g r i d and
2:'va r o d e , and o
I s t h e -x a to n tia l o f th e g r i d r e l a t i v e to t h e
su rr o u n d in g s p a c e .
O p e r a tin g on e q u a t io n 3 a l g e b r a i c a l l y
t o f in d t h e g r id p o t e n t i a l r e q u ir e d t o d e i o n i z e a g i v e n
e l e c t r o d e s t r u c t u r e In a g i v e n tim e for v a r io u s v a l u e s o f
arc c u r r e n t r e s u l t s In e q u a t io n 4 .
e, = KI0 * 467
( 4)
P lo t t in g , e q u a t io n 4 w i l l show t h a t beyond a c e r t a i n p o in t
t h e f u n c t i o n seams l i n e a r i n n a t u r e .
I t i s p o s s ib le th a t
1Yltteriborg did not i n v e s t i g a t e low c u r r e n t v a l u e s and so
m isse d t i n
r e la tio n sh ip .
The p r e s e n t stu d y in c lu d e d o n ly
t h e s e low c u r r e n t r e g i o n s and t h e c u r v a tu r e I s p l a i n l y
seen in fig u r e 1 1 .
B ecau ee o f l i m i t e d o u tp u t
x>wer ava' 1-
S b le from t h e I n v e r t e r i t was i m p o s s i b l e t o c a rr y th e t e s t s
t o h igh en o u g h c u r r e n t v a l u e s t o b e a b l e to o r e d i c t g r id
v o l t a g e needed t o e x t i n g u i s h th e tu b e wren p a s s in g rated
a v e r a ga anode amperea*
v i t t e n b e r g has s t a t e d t h a t t h e s h i f t i n e x t i n g u i s h ­
in g c o • t r o l c h a r a c t e r i s t i c i s a d e i o n i z a t i o n phenomena and
n o th in g i n t h e s e p r e s e n t t e s t a i s c o n t r a d i c t o r y o f t h a t
statem en t.
A s e r i e s o f c a l c u l a t i o n s was made to d e te r m in e the
e f f e c t o f t r a n s i e n t c u r r e n t and v o l t a g e s u r g e s on tube
d e io n iz a tio n .
These c a l c u l a t i o n s showed t h a t thou gh re­
s p e c t a b l e peal: v a l u e s o f "urge v o l t a g e s would be d e v e lo p e d ,
-
23 -
t h e lam p in g f a c t o r waa such t h a t t h e s e v o l t a g e s become
n e g l i g i b l e i n l e s s th a n one m icro seco n d and so t h e i r e f f e c t
c o u ld be i g n o r e d .
CONCLUSIONS
Ae e r e s u l t o f t H s s t u d y t h e f o l l o w i n g c o n c l u s i o n s
e r e d r Stvn r e g s r d t n r t h e v a r i a t i o n I n t h e c o n t r o l c h a r a c t e r ­
i s t i c s o f t h r e e elem ent t h y r a t r o n tu b e s a t h ig h e r - thri> pow er
frequencies:
1«
T h e r e w i l l i n r e n e r p . l b e two c o n t r o l c h a r a c t e r i s t i c s ,
a s t a r t i n g , or f i r s t cycle f i r i n g ,
co n tro l c h a ra c te ris­
t i c an d a n e x t i n g u i s h i n g c o n t r o l c h a r a c t e r i s t i c .
2,
The e x t i n g u i s h i n g c o n t r o l c h a r a c t e r i s t i c w i l l g e n e r a l l y
s h i f t n e g a tiv e ly w ith In c re a s in g frequency.
3,
The d i r e c t i o n and amount o f s h i f t I n s t a r t i n g c o n t r o l
ch aracteristic r l tl
ent,
I n c r e a s i n g f r e q u e n c y w i l l b e d ep en d ­
upon e l e c t r o d e g e o m e t r y a s f o l l o w s :
a) A n e g a t i v e s h i f t w i l l b e fo u n d f o r t h o s e t h y r a t r o n
tu b e s I n which t h e g r i d b a f f l e h o le i s o f e q u a l o r
g r e a t e r d iam eter th a n th e hole In the cathode heat
sh ield ,
b)
A p o s i t i v e s h i f t w i l l b e fo u n d f o r p o s i t i v e - g r i d
t h y r a t r o n t u b e s and a l s o f o r t h o s e n e g a t i v e - g r i d t h y r a ­
t r o n t u b e s where t h e b a f f l e h a s many s m a l l h o l e s b u t no
sin g le large hole.
c) D i r e c t i o n and amount o f s h i f t w i l l h e i n d e t e r m i n a t e
f o r t h o s e t h y r a t r o n tu b e s i n which t h e d i a m e t e r o f th e
g r i d b a f f l e hole I s Ie sa th a n t h a t o f th e hole In h eat
-
25 -
sh ie ld ,
4,
The s h i f t In s t a r t i n g c o n t r o l c h a r a c t e r i s t i c i s a
f u n c t i o n o f tu b e "dark* c u r r e n t s .
High v a l u e s o f g r id
"dark" c u r r e n t w i l l c a u se a s h i f t i n a o o s i t i v e d ir ­
e c t i o n w h il e h ig h v a l u e s o f anode "dark*
current w ill
c a u se a s h i f t i n a n e g a t i v e d i r e c t i o n .
5,
The e x t i n g u i s h i n g c o n t r o l c h a r a c t e r i s t i c s h i f t s nega­
t i v e l y w ith i n c r e a s i n g anode c u r r e n t .
F u r th e r stu d y o f t h i s s u b j e c t I s i n d i c a t e d t o t r y and
p r o v id e answ ers t o th e f o l l o w i n g q u e s t io n s :
1.
How w i l l t h e s t a r t i n g c o n t r o l c h a r a c t e r i s t i c o f t h r e e
e l e c t r o d e t h y r a t r o n tu b e s b eh ave w ith combined n e g a t i v e
d - c and phase s h i f t e d a - c v o l t a g e s a r o l l e d t o th e g r id ?
"Spike"or "p u lse" f i r i n g ?
2.
Tube d e i o n i z a t i o n i s a f u n c t i o n o f g r i d v o l t a g e ,
in ­
c r e a s i n g v a l u e o f n e g a t i v e g r id v o l t a g e w i l l s h o r te n
d e i o n i s a t i o n tim e ( s e e e q u a t io n 3 , page 21 and r e f e r e n c e
6).
With t h i s i n mind, can u per l i m i t s o f o p e r a t in g
fre q u en cy be e s t a b l i s h e d
f o r c o n v e n t io n a l t h y r a t r o n
t u b e s l i k e t h o s e s t u d ie d here?
3.
More c o m p le te i n v e s t i g a t i o n sh o u ld be made o f th e ex­
t i n g u i s h i n g c o n t r o l c h a r a c t e r i s t i c t o d e te r m in e whether
f a c t o r s o t h e r th a n tu b e d e i o n i z i n g c h a r a c t e r i s t i c s p la y
-
26 -
any p a r t and i f a o , how g r e a t a p a r t .
4,
From t h e s e s t u d i e s c a n a d e s i r e a b l e e l e c t r o d e g e o m e tr y
f o r h i g h - f r e o u e n c y t h y r a t r o n o D e r a t i o n b e deduced?
SELFEXCITFD
PAR AL L FL
INVERTER
- 2 4 VOLTS D - C
Vl = RECTIFIER TYPE A C VOLTVLt I VP RADIAl VANE A C VOLTMETER
VFO = VARIABLE FREOUF NCY AUDiO OSCILLATOR
FI GURE
i.
D. AGRAM
OF
C RCL T
FOR
TE S TI NG
T H > R a TRONS
28
, F A K ANODE-SUPPLY
5 00
/OLTS
I Sl NE
900
//AvE)
IOOJ
-O
J- C
FI GURE
2.
-5
OR. )
4
-3
-?
SUPPLY VOuTS
STARTING
TYPE
CHARACTERISTICS
FG- 5 7
THYRATRON
OF
29
PEAK
A N O D E - S UP P L Y
VuLTS
(SINE
IOOO
D- C
FIGURE
3.
STARTING
GRID SUPPLY
VuLTS
CHARACTERI STI CS
T H YR AT R ON
OF
TYPE
FG - 67
30
60 0
500
400
300
20v
100
-lO
-9
FIGURE
-8
4.
-7
D- C
-6
GRID
STARTING
TYPE
-C
-4
-3
SUPPLY VOLTS
-2
CHARACTERI STI CS
3C23
T HYRATRON
-I
OF
0
0
(SINt
. OLTS
70 0
ANODE -SUPPLY
800
PEAK
900
WAVE)
IOOC
31
PEAK
ANODE
SUPPLY
VOLTS
(SINE
WAVE)
IOOO
D-C
FI GURE
5.
GRID
STARTING
TYPE
SUFFLY
VOLTS
CHARACTERISTICS
FG-27A
T HYRAT RON
OF
32
_p
800
OV;;-
7v 0
600
5a
400
300
VOITS
r Vj >
ANODE - S U P P L Y
P
ISlNE
900
WAVE )
IO r O
100
8
-
FI GURE
7
- 0
0 C
6.
- 5
GRID
- 4 5 - 2
SUPPLY VOLTS
STARTI NG
TYP E
9C7
I
CHARACTERI S TI CS
T H YRATRQN
0
OF
PEAK
2C 0
33
(SINE
WAVE)
IOOO
o\o
PEAK
ANCDE-SUPPLY
VOLTS
OlUi
D-C
FI GURE
7.
GRID
S T ART I NG
TYPE
SUPPLY
VOLTS
CHARACTERISTICS
UX97 3
T HYRAT RON
OF
34
TUBE
DROP
CRITICAL GRID
VOLTAGE -----
ep =
eg :
APPLIED
ANODE
INDUCED
GRID
Ecc- D - C
X -
FIGURE
8.
TUBE
GRID
VOLTAGE
VOLTAGE
SUP PLY
VOLTAGE
FIRES
ANODE - GRID
COUPLING
IN
THYRATRON
PEAK
ANODE- SUPPLY
VOLTS
( SlNE
WAVE)
35
-16
FI GURE
9.
-14
D-C
-12
GRID
-IO
3
SUPPLY
E X T I N GU I S H I N G
FG - 5 7
CHARACTERISTIC
THYRATRON
7 8 ° CONDENSED MERCURY
0. I AMPERE
f = IOOO
-6
VOLTS
TEMPERATURE
AVERAGE ANODE
CYCLES PER
CURRENT
SECOND.
OF
TYPE
36
8 00 LU
700
Sr
$
LU
PT
60 O^
LD
50 u H
O
400
>
CL
3 O O^
2 0 O^
z
IOO ^
x
-22
-20
FIGURE
-16
-14
-12
D-C
GRID
10.
EXTINGUISHING
3023
7 6 °C.
Ol
-10
8
-6
SUPPLY
VOLTS
-4
CHARACTERI STI C
OF
T H Y R AT RON
CONDENSED
AMPERES
I = 1020
<
0 £
MERCURY
AVERAGE
CYCLES
PER
ANODE
TEMPERATURE
CURRENT
SECOND
TYPE
AV[- RAGE
ANJ DE
AMPF ^ F S
X IC 2
FG-2
74°C.
FIGURE
II.
EXTINGUISHING
GRID
VOLTS
VERSUS
AVERAGE
ANODE
CURRENT
38
-A IGL K
-ANODE
HuLt
/U A I-H E
/HOufc
/ U m H-LE
* ORIC
Ir -GRIL
HfcAT Sdi fc-D
* I- Dfc
ANODE
HOLE
GRID
ri L AMfcAr"
HEAT C H l E l f
-,/Vr -Ior '-
nC?
Er' -5"'
, - c " /'
AN TDF
•GRID
UX
‘r C- 07
ANODF
y S HI ELD
, CATHODE
2050
7: 2 7
FIGURE
12.
2051
ELECTRODE
C ON S T R U C T I ON
OF
THYRATRONS
-
39 -
APPENDIX I
Q
I t c a n bo shown
t h a t i n any p a r a l l e l n e t w o r k o f
impedances t h e c u r r e n t I .
i n any b r a n c h A o f t h e n e t w o r k
may b e c a l c u l a t e d b y t h e e q u a t i o n
•
1A =
A
1O
Z'+ ' b
where I q - t h e t o t a l c u r r e n t t o t h e two p a r a l l e l b r a n c h e s
A and B.
2. = t h e impedance o f b r a n c h A
Zp * t h e Im p ed a n ce o f b r a n c h B
The e q u i v a l e n t c i r c u i t o f a t h r e e e l e c t r o d e t h y r a t r o n
t u b e i n r e c t i f i e r s e r v i c e , t u b e nor*-conducting, g r i d b i a s
voltage zero,
Figure
where
13.
c a n b e r e p r e s e n t e d a s shown b y f i g u r e 13
Equivalent circuit of thyratron .
= load r e s is ta n c e
C1 = a n o d e - c a t h o d e c a p a c i t a n c e
Cp = a n o d e - g r i d c a p a c i t a n c e
C_ = g r i d - c a t h o d e c a p a c i t a n c e
40
Eq =
rms anode supply
Rg = gr i d
Using
assuming
'3
voltage
r esi stance
pri nci pl es
sinusoidal
outlined
voltages
in the
reference
cited,
and currents:
-JX 3
Rfl - JX
= '!
'2 =
the
-
-jX,
1O
= I.
X 1( R a - j X J
'( X lH-X2-I-X3)Rg - J X 3(X 1-I-Xe)
1E ' ^ rS t]
1O
=
EP
j X| ^ jX 2Rl X H-X2
I X HI- Ji X1
JX3Rq
Rfl - JX :
RflX3
g J^3 J
Rg(Xl-HX2H-X3)- J X 3(XlH-Xe)
= E
p RuRg(XlH-X2HX3) - X l X eX3-J[R l X3(X iHX2)H R 9X i (XeH-X3)I
Xl (Rq- J X 3)
1Z
"
Ep
Rl Rq(X i H-X2HX3) —X, X2 X 3 - J t R uX3(XlH-X2)HRgXl(XeHX3)]
, _____________________ - j x , x __________________________
Lp Rl Rg(XlHX 2HX 3) - X , X2 X3 -JC rl X3(X1H X 2) + RgX l (X2HX5)]
The
voltage
drop over the grid resistance
is
- j EpRgXl X 3
E „ - LR.=
9
3 9 Rl R (X 1H-X2H X 3) - X l XeX 3-JCRuX3 (Xl H X 2) H R gXl (X2HX3)]
and
41
-
The g r i d r e s i s t a n c e Fj, I e i n p a r a l l e l w i t h t h e c a p a c i ­
t a n c e C_, t h e g r i d - c a t h o d e c a p a c i t a n c e , and t h e p o t e n t i a l
d r o p w i l l h e t h e same o v e r e a c h o f t h e s e e l e m e n t s .
H en lac­
i n g t h e rme v o l t a g e s b y t h e I n s t a n t a n e o u s v o l t a g e s i n
e q u atio n 3 r e s u l t s In the follow ing equation fo r th e ins­
ta n t a n e o u s v o l t a g e Induced I n t o t h e g r i d c i r c u i t o f th e
t h y r a t r o n by I n t e r e I e c t r o d e c a n a c i t s n e e s
Xa
e,
RuRfl(X |+XlfI-Xs) “ X, XeXsH C R uX8(X ^ X 8)+ R flXl(X ^ X 5)]
Since th e i n t e r e l e c t r o d e c a p a c ita n c e s are v ery sm all,
g e n e r a l l y o n l y a few m i c r o - m i c r o f a r a d s , t h e i r r e a c t a n c e s
w i l l b e v e r y l a r g e and so e q u a t i o n 4 may b e a o p r o Z l mated
w ith very l i t t l e
e
8
J
e r r o r by
®o^g
(5)
42
-
A ? ■SNDIX I I
I c e o r d i ic t o 3 a y - L u e a a c ' s law f o r o e r f e c t g a s e s a t
c o n s t a n t volume
where
f . = p r e s s u r e a t t e m p e r a t u r e T1
Pg -
and
p r e s s u r e a t t e m p e r a t u r e Tg
T-l , Tg a r e i n a b s o l u t e d e g r e e s .
Assuming t h a t t h e m e r c u r y v a p o r i n a t h y r a t r o n t u b e
w i l l obey t h e p e r f e c t g a s l a w , t h e n t h e p e r c e n t i n c r e a s e
i n p r e s s u r e ( s i n c e volume i s c o n s t a n t )
as th e condensed
m e r c u r y t e m p e r a t u r e i s i n c r e a s e d from 53° C. t o 78
( o r 3 2 6 ° A . t o 3 5 1 ° A) w i l l b e
3 5 1 - 3 26
326
x 100 =
2500
326
- 7.97%
C.
- 43 APPENDIX I I I
The s t a r t i n g o f
i a r a l l e l i n v e r t e r s designed to oper­
a t e s e l f - e x c i t e d i n th e au d io-frequency range Is o f te n
rathe"'- " l f f l c u I t .
Sim n ly c l o s i n g t h e d - c e u o o l y v o l t a g e
sw itc h does not as a g e n e r a l r u l e provide a t r a n s i e n t
g r i d vo t a g e o f s u f f i c i e n t m a g n i t u d e and d u r a t i o n t o I n i ­
t i a t e in v e rte r actio n .
To a s s u r e e a s y a nd c e r t a i n s t a r t i n g
o f t h e I n v e r t e r u s e d i n t h i s s t u d y t h e c i r c u i t shown b e lo w
was i n v e n t e d o n August 1 7 , 1 9 4 3 , b u i l t u p and t e s t e d by
March 2 , 1949 and o p e r a t e d s a t i s f a c t o r i l y t h r o u g h o u t t h e
e x p e r i m e n t a l - work c o n d u c t e d t h e r e a f t e r .
The o D e r a t i o n o f t h e s t a r t i n g c i r c u i t i s a s f o l l o w s :
the
o s i t i v e te r m in a l o f th e d - c g r i d b i a s supply v o lta g e
i s co n e c t e d t o t h e c a t h o d e s o f t h e i n v e r t e r t u b e s t h r o u g h
a n o r m a l ly , c l o s e d c o n t a c t o f t h e " S t a r t ” push b u t t o n .
p o te n tio m e te r t a p i s connected to t h e center
The
ta p o f the
s e c o n d a r y w i n d i n g o f t h e g r i d t r a n s f o r m e r and p r o v i d e
j
a
means o f v a r y i n g t h e d - c g r i d b i a s v o l t a g e o f t h e I n v e r t e r
tubes.
P r e s s in g th e " S t a r t " push b u t t o n th e n does th e
follow ing;
1 . ) D isco n n ects th e p o s i t i v e te r m in a l of the d -c g r i d
b i a s s u p )ly v o l t a g e from t h e c a t h o d e s o f t h e
In v e rte r tubes.
2 . ) Connects th e n e g a t iv e t e r m i n a l o f the d - c g r i d b i a s
44 -
supply v o lta g o to th e cathodes o f th e I n v e r t e r
tubes,
3 . ) Connects th e s e r i e s arrangem ent o f s t a r t i n g re ­
s i s t a n c e and s t a r t i n g i n d u c t a n c e t o t h e d - c b i a s
supply v o l t a g e ,
4 . ) C o n n e c t s t h e j u n c t i o n o f s t a r t i n g r e s i s t a n c e and
s t a r t i n g inductance to the g rid o f i n v e r t e r
t u b e T2.
As a r e s u l t o f s t e p 3 ab o v e a d - c t r a n s i e n t i s pro­
d u c e d i n t h e Ms t a r t i n g " c i r c u i t ,
t h e d u r a t i o n o f which i s
d e t e r m i n e d b y t h e r e l a t i v e v a l u e s o f Rfl and L .
tran sien t,
This
through the connection d escrib ed i n s te p 4
ab o v e a p p l i e s a h i g h p o s i t i v e p u l s e o f v o l t a g e t o t h e grid:
o f I n v e r t e r t u b e T2 and so I n i t i a t e s o p e r a t i o n o f t h e
Inverter,
R eleasin g the " S ta r t" p u sh -b u tto n causes th e " s t a r t ­
i n g " c i r c u i t t o b e d i s c o n n e c t e d from t h e I n v e r t e r and
econneots th e p o te n tio m e te r f o r usual n e g a tiv e g r id b ia s
v ariatio n .
u m iffij
^rmmrrrnnr
,
r 0 W cr
r (^)' ^ ©
'
ot"*")
>
DC
SUPPLY
VOLTAGE
0M
♦
>
_j
a.
I o
Q
X
< CS
T2 S
M jjO U
r
i- z: 3 5
(/) < CD>
I
^
- .f
fT Ipffl
TI1TP -- INVERTER TUBES
(EG - 6 7
Rg
GRID RESI STOR ( 2 0 0 0 OHM)
L - D C CHOKE ( 0 , 2 HENRY)
Cc
COMMUTATING CAPACITANCE ( 0 . - 5 mtd )
Rn = GRID PHASE- SHIFT RESISTANCE ( 0
2 0 0 OHMS)
Cp
GRID PHASE - SHL T CAPACITANCE ( 0. 02 3 mfd.)
’ P TiS
NVEPTER TRANSFORMER
T2P, T2S GRID TRANSFORMER
FI GURE
14
SELF - EXCI T E D
PARALLEL
I NVERTER .
PB. START
r - |- - i
O I o—l
GRID BiAS S U P P L <
FIGURE
15
I NVERTER
STARTING
CIRCUIT
VOLTAGE
TI , T2=INVERTER TUBES
Rq- GRID RESISTORS
T^S =GRID TRANSFORMER SECONDARY
P= D-C GRID BIAS POTENTIOMETER
Rs = STARTING RESISTANCE
U - S T A R T ;NG INDUCTANCE
RB. START
MOMENTARY CONTACT PUSH BUTTON
‘iT —
LITERATJTRS CITED AMD CONSULTED
>
1.
DEIO IZATIOM CONSIDERATIONS IM A HARMONIC GENERATOR
? DYING A GAS TUBE 3 , ITCH. A. 0 . S h e p p a r d .
P r o c e e d i n g s , I n s t i t u t e o f R a d i o E n g i n e e r s , New York,
. Y . , volume 3 1 ,
2.
F e b r u a r y 1 9 4 3 , p a g e s 66 - 7 4 .
F...E';jENCY PEMFORiAMCE OF THY^iT/.OMS,
H.
itten b erg .
AIEP T r a n s a c t i o n s , volume 6 3 , 19^i6, December s e c t i o n ,
p a g e s 843 - 8 4 8 .
3.
••• VAPIABL! r
G riffin .
;s
4.
UENCY ELECTROHC GENERATOR, D. A.
E l e c t r o n i c s , New Y o r k , N, Y. S e p t e m b e r 19 4 3 ,
I ?o .
THEORY AND APPLICATION OF ELECTRON
K. I .
Reich.
TUBES (book)
Ne Graw H i l l Book Company,
lew York,
N. Y . , 1 9 3 9 .
MACHINERY ( b o o k ) . B r y a n t and
Johnson.
1935.
6.
Plc Graw H i l l Book Company,
New Y o r k ,
I. Y . ,
C hapter 32.
G aSE US CO PDUCTO 5 (book) „
J . D. C o b i n e .
Re Craw
H i l l Book Company, New Y o r k , N. Y . , 1 9 4 1 .
V.
.
P ren tice-H all I n c . ,
. D.
tew Y o r k , N . Y . , 1 9 4 7 .
CIRCUITS (book). K.Y. Tang, I n t e r -
n p t i o n a l Soxtbook C o .,
'c ra n to n ,
P a ., 1940, C h a p te r 7.
MONTANA STATE UNIVERSITY LIBRARIES
CO
III I 762
I I I ! 100
111 15523
Il Eli !III
1
N578
Sn9%v.... cop. 2
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