PU1000/PU600 INSTALLATION MANUAL
10229-15.doc
Polyamp AB, Sweden
www.polyamp.com
Page
6 (10)
Figure 1. Current share connection with series
diode.
3.3 Voltage adjustment with current
sharing
The converters must be running with 5% of nom.
load or more, and the ”current share” must be
connected. If each converter output voltage is
adjusted to the same voltage, which they are at
delivery, the yellow ”C. MASTER” LED might be
lit on most units.
To
increase
the output voltage:
1.
Choose a unit where the ”C. MASTER” LED is
lit. Turn the V.ADJ potentiometer clockwise
until you reach your desired output voltage.
2.
The other units should now also be adjusted to
approximately the same output voltage,
otherwise the output voltage will drop if the
master converter breaks down. Turn the V.ADJ
potentiometer slowly clockwise on the other
units until the ”C. MASTER” LED is lit or
almost lit.
To
decrease
the output voltage:
1.
Turn the V.ADJ potentiometer approximately
one (1) turn counter clockwise on all converters
but one. This will not affect the output voltage
yet.
2.
Turn the V.ADJ potentiometer counter
clockwise on the remaining converter (if your
load current exceeds 5% of the total rated
current, this should be the only unit with the ”C.
MASTER” LED lit) until you reach the output
voltage you desire. (If you turn more than one
(1) turn counter clockwise you must repeat from
step 1).
3.
The other units should now also be adjusted to
approximately the same output voltage.
Otherwise the output voltage will drop if the
master converter breaks down. Turn clockwise
on the V.ADJ potentiometer on the other units
slowly until the ”C. MASTER” LED is lit or
almost lit.
4 Multiple loads at the output
If you are using several loads, we recommend
fusing them separately with fast acting fuses on the
positive output branch. Some considerations
regarding short-circuits should be taken. See below.
4.1 Short-circuits
1.
If there is a short-circuit in one branch and the
total current in all branches
does not
exceed
105% of the nominal current of the converter
(see label on front panel), the output voltage
will not be affected. The time for the fuse to
blow can be calculated from the data sheet of
the fuse if you know the short-circuit current
trough the fuse.
2.
If there is a short-circuit in one branch and the
total current in all branches
does
exceed 105%
of the nominal current of the converter, the
output voltage will drop until the fuse is blown.
Depending on the impedance of the short-circuit
(whether it is abrupt or merely an overload) and
the resistance of the load cables, the effects of a
short-circuit will vary.
Long cables reduce short-circuit currents,
resulting in longer delay until the fuse is blown
and hence an increased voltage dip. Light
overload does not necessarily result in a blown
fuse.
To reduce the voltage drop at short-circuit and
if any branch has more than approximately 30%
of the total output current of the converter, a
large external capacitor is recommended. Such a
capacitor will supply the peak current needed to
blow the fuse, see
Figure 2
. To calculate the
capacitor needed, use the following formula:
C = 1.2 x ( I
S
x
Δ
t ) /
Δ
U
1.2 = Safety margin.
I
S
= Short-circuit current through the fuse.
Δ
t = Time before the fuse blows (see data
sheet on the fuse).
Δ
U = Acceptable voltage dip before the fuse
blows.
Example:
You have a 5A fuse with fast characteristic and
the short-circuit current is 50A. The data sheet
