TRILUX Luminaires - Proljus AB

Suppression choke
For remote switching of outdoor lighting
systems, ripple control signals are used
occasionally which are superimposed on the
mains voltage as high-frequency signals with
frequencies ranging between 110 Hz and
Dangerous switching resonances
2000 W metal halide lamps, e.g. in spotlights,
are operated on a mains voltage of 400 V.
Fig. 3.4 shows a corresponding connection of
three lamp circuits, which are uniformly distributed
to the three phase conductors of the
mains. As long as neither a phase conductor
fails due to a mains incident nor a defective
fuse interrupts the supply cable, this circuit
is stable.
As a result of unequal temperature elevation
of the lamp electrodes, rectifier effects can
occur during the switch-on process that almost
totally suppress the current-limiting
function of the choke. The consequences are
short-time currents of up to 50 times the operating
current, thereby causing improperly
dimensioned fuses to trip (fig. 3.5). If a phase
conductor, e.g. L2, is interrupted by the failure
of its protecting fuse, the lamps La1 and
La2 are in series and the lamp with the highest
operating voltage will fail. In the other
La3 D3
La1 La2
C3
D1 D2
K1 K2
L1 L2 L3
3.4 Distribution of three
lamp circuits to three phase
conductors.
1600 Hz. To avoid signal degradation due to
the compensation capacitor being installed
parallel to the mains in the floodlight, a suppression
choke has to be connected in series
with the capacitor. This can be requested on
site.
circuits, high resonance currents I res, which
depending on the capacity of the capacitor
and the inductance of the choke, e.g. four
lamps per circuit, can be up to 80 A and
can destroy lamps and control gear, will be
induced as a result of the resonances of the
oscillation circuit consisting of inductors and
capacitors.
Similar resonance phenomena may occur,
if in a circuit similar to figure 3.5, the neutral
conductor N (mid-point conductor) is connected
instead of the phase conductor L2
and this neutral conductor is interrupted.
The highest resonance currents occur when
there are up to four lamps per circuit. With
the centralised compensation of five lamps
or more, the resonance phenomena will
generally no longer occur, because the capacitance
of the implemented compensation
capacitors is too high to form an effective resonance
circuit with the choke inductances.
La1 La2
Ires
D1
K1
OFF
L1 L2 L3
defective
D2
K2
3.5 Two HIT 2000 W (400 V)
floodlights, where the fuse in
L2 is tripped.
L1
L2
L3
D1
La1
K1
Si Si
La2
D2
K2
Si Si
L1 L2 L3
La3
D3
K3
Si Si
3.6 Distribution of floodlights to
three phase conductors, each
feeder is protected separately.
Resonances are effectively prevented in
TRILUX floodlights by installing a fuse for
each phase conductor (fig. 3.6). This protects
the circuit against high resonance currents.
If a fuse trips, the circuit it protects is interrupted
and the linkage with other circuits
and thus the high resonance currents are
safely avoided.
Another safety mechanism is a three-pole
phase monitor that shuts down the entire
installation if only one of the phases has
failed as a result of the described causes
(fig. 3.7).
L1
L2
L3
D1
La1
K1
Si Si
D2
La2
K2
Si Si
L1 L2 L3
D3
La3
K3
Si Si
Ph
3.7 Distribution of floodlights
to three phase conductors,
mains cable with 3-pole phase
monitor.
355
Technical information