19
Subject to change without notice
Parallel operation
In order to increase the total available current the outputs of
supplies can be paralleled. The output voltages of the supplies
involved are adjusted as accurately as possible to the same value.
In this mode it is possible that one or more supplies enter the
current limit mode. The output voltage remains in regulation as
long as still at least supply is in the voltage control mode. It is
recommended but not absolutely necessary to fine adjust the
voltages such that the individual current contributions remain
nearly equal. Of course, the maximum available output current is
the sum of the individual supplies‘ maximum currents.
Example:
A load draws 0.7 A at 12 V. Each output of the HM 8040-3 is
specified for 0.5 A. In order to supply the 0.7 A both outputs have
to be set to 12 V. Then the respective output safety terminals have
to be connected in parallel (black to black, red to red). The load is
connected to one of the supplies. By depressing OUPUT
the
outputs are activated . As a rule one output will supply appr. 500
mA in current limit mode, the other the balance of 200 mA in
voltage control mode.
If you parallel power supplies made by HAMEG and
those of other manufacturers please make sure that the
individual current contributions of the supplies involved
are as equal as possible. HAMEG supplies are designed
for series and parallel operation. If supplies of other
manufacturers are used in a parallel connection which
are not overload protected damage may occur if the
individual currents are unequal.
Current limiting
means that a maximum current can be set. This is e.g. useful in
order to protect a sensitive test circuit. In case of an inadvertent
short in the test circuit the current will be limited to the value set
which will in most cases prevent damage.
The picture shows that the output voltage V
out
remains stable,
while the current I increases until the current limit selected will be
reached. At this moment the instrument will change from constant
voltage regulation to constant current regulation. Any further load
increase will cause the current to remain stable while the voltage
decreases ultimately to zero.
Electronic fuse
This feature provides a still better protection of sensitive loads,
especially of such loads which require more than one voltage: if
one current limit is reached all output voltages will be disconnected
immediately. In order to turn these back on the pushbutton
OUTPUT
must be depressed.
Concept of the HM 8040-3
The triple power supply HM8040-3 features 3 independent output
voltages. In addition to supplying 3 voltages the 0 .. 20 V outputs
may be connected in series or parallel.
Exceeding 42 V
If all outputs are series connected the sum can exceed
42 V. In this case touching of live parts may cause
danger of life! It is assumed that only qualified and
extensively instructed personnel is allowed to operate
these supplies and their loads.
In series connection the maximum current is 0.5 A. By paralleling
the outputs a maximum of 1 A is possible. The maximum voltage
remains 20 V. Please note that the specifications (e.g. impedance,
noise, regulation) listed for individual use of the outputs may
change if series or parallel connected.
Output power
As the HM 8040-3 is fed from the mainframe supplies in the
HM 8001-2 (predecessor HM 8001) its maximum output power is
limited to 25 W. Sufficient ventilation is necessary.
The operation of 2 HM 8040-3 in the HM 8001-2 is
only permitted if the sum of all output currents
(these are 6) remains
≤
≤
≤
≤
≤
2 A.
Overtemperature protection
If the internal temperature exceeds 75 .. 80 degrees C all outputs
and displays will be deactivated. This will be indicated by 3
blinking dashes in the left and right displays. As soon as the
displays will light up again and display the values set the instrument
will be ready for operation. In order to turn the outputs back on the
pushbutton OUTPUT
has to be depressed.
Switching the outputs on/off
It is a feature of all HAMEG power supplies that the outputs can
be turned on and off by pushing a button. The power supply
remains turned on so that all voltages and currents may be set
prior to turning the outputs on.
STOP
+
-
+
-
+
-
U
= U = U = U
1
2
3
total
I
= I + I + I
total
1
2
3
U
3
U
2
U
1
I
2
I
3
I
1
Power supply 1
Output 1
Power supply 1
2
Output
Power supply 2
1
Output
I
out
U
out
U
const
I
max
Current limit
Adjustment of current
Adjustment
of
volt
age
STOP
STOP
Concept of HM 8040-3
Содержание HM8040-3
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