Current Limit; Electronic Fuse - Hameg HM7042-5 User Manual

B a s i c s o f p o w e r s u p p l i e s
In this mode the output voltages add, the output
current is the same for all supplies. As the sum of all
voltages may well surpass the 42 V limit touching
of live parts may be fatal! Only qualified and well
instructed personnel is allowed to operate such
installations.
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 one supply is
in the voltage control mode. It is recommended but not
a solutely necessary to ne ad ust 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 requires 12 V at 2.7 A. Each 32 V output of the
HM7042-5 can deliver 2 A. First set both supplies to 12 V.
Then connect both black and both red safety connectors
respectively in parallel. The load is connected to one of the
supplies. With the pushbutton OUTPUT
be turned on. It is normal that one output will current limit
at 2 A while the other will contribute the balance of 0.7 A
in voltage regulation.
In case you should parallel power supplies of other manuf-
acturers with HM7042-5 power supplies make sure all are
specified for this mode of operation. If one supply of those
connected in parallel should have insufficient overload
protection it may be destroyed. HM7042-5 power supplies
are specified for series and parallel operation.
3.4

Current Limit

Current limit 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.
北京海洋兴业科技股份有限公司（证券代码：839145）
U
out
U
const
The picture shows that the output voltage V
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
U
out
current regulation. Any further load increase will cause
the current to remain stable while the voltage decreases
ultimately to zero. U
const
3.5
In order to provide a still better protection than current
limiting offers the HM7042-5 features an electronic fuse.
As soon as I
simultaneously disabled. They may be turned on again by
depressing OUPUT
the voltage will
Adjustment of current
Current limit

Electronic Fuse

is reached all outputs will be immediately
max
.
short cut at
approx. 20% of I
max
I
I
max
out
remains
out
Current limit
starts at 110% of I
max
I
I
max
out
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