Technical information

27
6
.
3
.1
L
ea
ki
ng arc tu
be
High
temperatures an
d
pressures
i
n t
h
e arc tu
b
e, t
h
e
a
gg
ressive chemical substances in the tube and the
thermal cyclin
g
o
f
a lamp place extreme strains on
the arc tube. This can cause the tube to leak, allowin
g
startin
g
g
as and
f
illin
g
particles to enter the outer bulb.
Dependin
g
on the size o
f
the leak, this e
ff
ect is usually
a
g
ra
d
ua
l
process.
I
t
i
s
i
n
i
t
i
a
ll
y not
i
ce
d
b
y a cons
id
er
-
able change in the light colour. Increasing leaks o
f
start
i
n
g
g
as
i
nto t
h
e outer
b
u
lb
can resu
l
t
i
n t
h
e
di
s
-
char
g
e process movin
g
f
rom the arc tube to outer bulb
di
sc
h
ar
g
e
.
–
F
or
l
am
p
s w
i
t
h
evacuate
d
outer
b
u
lb
, var
i
ous a
b
-
norma
l
di
sc
h
ar
g
e states can occur,
d
epen
di
n
g
on
tube
f
illing pressure and outer bulb volume
.
–
For lamps with
g
as-
f
illed outer bulb, usually
lam
p
s
>
400 W,
g
low dischar
g
e and incandescent
mo
d
e
d
o not occur.
P
art
i
cu
l
ar
ly
i
n
l
amps operat
-
in
g
with i
g
nition units, the described
f
aults result
i
n a
di
rect arc
di
sc
h
ar
g
e.
I
n extreme causes, t
hi
s
c
an cause t
h
e
l
am
p
to
b
urst
.
In th
e
case
of
gl
ow
di
sc
h
arge, t
h
e vo
l
ta
g
e across
the lamp is hi
g
h but only very low current.
S
putterin
g
causes mater
i
a
l
to
b
e
d
e
p
os
i
te
d
on t
h
e outer
b
u
lb
.
I
t
i
s
possible
f
or
g
low dischar
g
e to precede arc dischar
g
e.
Th
e tem
p
eratures
i
n t
h
e
pi
nc
h
e
d
area are
l
ower t
h
an
i
n
n
orma
l
o
p
erat
i
on
.
In th
e
case
of
a
rc
di
sc
h
ar
ge
,
t
h
e vo
l
ta
g
e across t
h
e
l
amp
i
s
l
ow an
d
t
h
e current
i
s
li
m
i
te
d
by
t
h
e c
h
o
k
e.
Th
e
a
tt
ac
hm
e
nt
of
th
e
a
r
c
o
nt
o
th
e
l
eads
in th
e
ou
t
er
bulb can cause these to melt. The hi
g
h temperatures
cause the material o
f
the leads to eva
p
orate and then
settle on the outer bulb. The hot arc near the
p
inch
-
in
g
area can result in hi
g
h temperatures
(
in extreme
cases the
y
can exceed 800 °C). At the contact between
soc
k
et an
d
l
amp
h
o
ld
er an
d
at t
h
e e
l
ectr
i
ca
l
contact, t
h
e
temperatures are natura
lly
muc
h
l
ower.
H
ere
i
n extreme
cases 300 °
C
were measured at the contact between lam
p
Fi
g
. 29: Various states o
f
outer bulb dischar
g
e
G
low dischar
g
e Arc dischar
g
e Incandescent lamp mode
and lam
p
holder and 250 °
C
at the electrical contact of the
l
am
p
pi
n to t
h
e
l
am
p
h
o
ld
er.
Th
e e
l
ectr
i
ca
l
contact
i
s a
l
so
relevant for the Tem
p
erature
C
ode of the socket
(
see also
cha
p
ter 7.3 lam
p
holder
)
.
I
f
metallic coatin
g
s in the pinchin
g
area
f
orm throu
g
h
m
aterial deposition
f
rom the leads so that the
y
f
orm a
cont
i
nuous con
d
uct
i
ve
l
a
y
er
b
etween t
h
e
l
ea
d
s, t
h
en
t
he
r
esul
t
i
n t
he
so
-
called
i
n
ca
n
desce
nt m
ode
.
The
metal coatin
g
o
ff
ers su
ff
icient resistance that power is
consume
d
an
d
t
h
e coat
i
n
g
b
e
gi
ns to
gl
ow.
I
t
i
s
h
ere
b
y
poss
ibl
e t
h
at e
l
ectr
i
ca
l
va
l
ues s
i
m
il
ar to norma
l
opera-
tion are reached, which would make it im
p
ossible
f
or
an electronic ballast
f
or example to detect this abnor-
ma
l
s
i
tuat
i
on.
Thi
s a
l
so causes
hi
g
h
temperatures
i
n
t
h
e p
i
nc
hi
n
g
area
.
G
low and arc dischar
g
es can be detected by current
and volta
g
e values deviatin
g
f
rom the normal levels, so
t
h
at an e
l
ectron
i
c
b
a
ll
ast w
i
t
h
a correspon
di
n
g
automat
i
c
cut-out
f
eature can switch o
ff
such lam
p
s. In addition,
the luminaire desi
g
n must use components resilient to
high
t
h
erma
l
l
oa
d
s so t
h
at t
h
e poss
ibl
y
high
tempera
-
tures will not lead to harm
f
ul situations
f
or the o
p
erator
.
6
.
3
.
2
I
ncrease
i
n re-
ig
n
i
t
i
on pea
k
The re-i
g
nition peak is a peak in the lamp volta
g
e a
f
ter
the zero crossin
g
o
f
current and volta
g
e. For sinusoi-
d
a
l
l
amp current, t
h
e current
d
ecreases
g
ra
d
ua
ll
y
b
e
-
f
ore the zero crossin
g
. As the plasma is heated by the
current
f
low, a decrease in current causes the
p
lasma
to cool down and reduces its conductivit
y
. A
f
ter the
zero cross
i
n
g
, t
h
e coo
l
e
d
p
l
asma can
i
n
i
t
i
a
ll
y no
l
on
g
er
conduct the current throu
g
h the lamp. As the current
d
oes not r
i
se t
h
rou
gh
t
h
e
l
amp, an
i
ncreas
i
n
g
amount
o
f
supply volta
g
e
f
alls across the lamp. The rise in
volta
g
e causes the ionization o
f
the plasma and there
-
f
ore the current to increase a
g
ain, meanin
g
the plasma
is rei
g
nited, hence the name “re-i
g
nition peak”. I
f
the
re-
ig
n
i
t
i
on pea
k
excee
d
s t
h
e
l
eve
l
t
h
at can
b
e prov
id
e
d
b
y t
h
e supp
l
y vo
l
ta
g
e, t
h
e
l
amp
g
oes out
.