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EA Elektro-Automatik GmbH
Helmholtzstr. 31-33 • 41747 Viersen
Germany
Fon: +49 2162 / 3785-0
Fax: +49 2162 / 16230
www.elektroautomatik.de
PS 9000 T Series
3.2.2 Current regulation / constant current / current limiting
Current regulation is also known as current limiting or constant current mode (CC).
The DC output current is held constant by the power supply, once the output current to the load reaches the adjusted
limit. Then the power supply automatically switches The current flowing from the power supply is determined by the
output voltage 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 sets the output current
according to I
MAX
= P
SET
/ U
IN
, even if the maximum current value is higher. The current set value, as determined
by the user, is always an upper limit only.
While the DC output is switched on and constant current mode is active, then the condition “CC mode active” will
be indicated on the graphic 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 a status message via digital interface.
3.2.3 Power regulation / constant power / power limiting
Power regulation, also known as power limiting or constant power (CP), keeps the
DC output power of a power supply constant if the current flowing to the load in
relation to the output voltage and the resistance of load reaches the adjusted value
according to P = U * I resp. P = U² / R. The power limiting 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
output voltages higher current flows and vice versa in order to maintain constant
power within the range P
N
(see diagram to the right).
While the DC output is switched on and constant power mode is active, then the
condition “CP mode active” will be shown on the graphic display by the abbrevia-
tion CP, as well stored as status which can also be read as a status message via
digital interface.
3.2.3.1 Power derating
Due to fusing and cross sections of conductors and the extended supply voltage range, power supply models with
1500 W rated output power have a fixed derating, which becomes active below a certain input voltage level (for
value see
„1.8.3. Specific technical data“
). It then derates the maximum available output power down to approx.
1000 W. The derating only affects the power stage, so the full range for power set value adjustment remains,
though the device will not provide full output power anymore. In this situation, constant power operation can not
be indicated by status “CP”. Active derating can then only be detected by reading the actual values of voltage and
current and by calculating the power.
No status “CP” available if the adjusted power set value (Psel) is bigger than the derated actual
output power of the device. It means, derating is not signalled anywhere.
