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EA Elektro-Automatik GmbH
Helmholtzstr. 31-37 • 41747 Viersen
Germany
Fon: +49 2162 / 3785-0
Fax: +49 2162 / 16230
www.elektroautomatik.de
PSB 9000 3U Series
Depictions:
Example for neg. load step: the DC output will rise
above the adjusted value for a short time. t = transient
time to settle the output voltage.
Example for pos. load step: the DC output will collapse
below the adjusted value for a short time. t = transient
time to settle the output voltage.
3.3.2
Current regulation / constant current / current limiting
Current regulation is also known as current limiting or constant current mode (
CC
).
The current in the DC terminal of the device is held constant once the output current (source mode) to the load
resp. the current consumed from the load (sink mode) reaches the adjusted limit. Then the device automatically
switches to CC. In source mode, the current flowing from the power supply is only determined by the output volt
-
age and the load’s true resistance.
As long as the output current is lower than the adjusted current limit, the device will be either in constant voltage
or constant power mode. If, however, the power consumption reaches the set maximum power value, the device
will switch automatically to power limiting and set voltage and current according to P = U * I.
While the DC power stage is switched on and constant current mode is active, the condition “CC mode active” will
be indicated on the graphics display by the abbreviation
CC
and this message will be passed as a signal to the
analog interface, as well stored as status which can also be read as via digital interface.
3.3.3
Power regulation / constant power / power limiting
Power regulation, also known as power limiting or constant power (
CP
), keeps the
DC power constant if the current flowing to the load (source mode) resp. the current
from the source (sink mode) in relation to the voltage reaches the adjusted limit
according to P = U * I (sink mode) resp. P = U² / R (source mode).
In source mode, the power limiter then regulates the output current according to
I = sqr(P / R), where R is the load’s resistance.
Power limiting operates according to the auto-range principle such that at lower
voltages higher current can flow and vice versa, always in order to maintain constant
power within the range P
N
(see diagram to the right).
While the DC power stage is switched on and constant power mode is active, the
condition “CP mode active” will be indicated on the graphics display by the abbre-
viation
CP
, as well stored as status which can also be read as a status message
via digital interface.
When using remote sensing in source mode, the device usually delivers a higher voltage on
the DC output than adjusted, which results in an additional power due to line losses and may
cause the device to enter power limitation without explicitly indicating “CP” in the display. In sink
mode, the CP status is correctly displayed for the power consumed from the source.
