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EPS Stromversorgung GmbH
Alter Postweg 101 • 86159 Augsburg
Germany
Fon: +49 821 / 570451-0
Fax: +49 821 / 570451-25
PS 9000 1U Series
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 the load reaches the adjusted
power value according to P = U * I resp. P = U² / R. The power limitation then regu
-
lates 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)
Constant power operation primarily impacts the output current. This means, the
adjusted maximum output current can not be achieved if the maximum power value
limits the output current according to I = P / U. The adjustable set value of current,
as indicated in the display, is always only an upper limit.
While the DC output is switched on and constant power mode is active, then the condition “CP mode active” will
be shown on the display by the abbreviation
CP
and can also be read as a status message via digital interface.
3.2.3.1 Power derating
The power supplies of series PS 9000 1U offer an extended AC supply voltage range, but are dedicated for the
use at typical 230 V
AC
, ±10%. Below a certain supply voltage, all models will automatically start to derate, i.e.
reduce the maximum available output power. The derating happens on the AC input side and thus the device will
not indicate the derating condition as “
CP
” (constant power resp. power limitation).
Depending on the nominal power of the particular model, the derating acts at different supply voltages:
•
3 kW models
▪
Below approx. 207 V
AC
: Derating to max. 2500 W output power
▪
Below approx. 180 V
AC
: Shutdown of the DC output
•
1.5 kW models
▪
Below approx. 150 V
AC
: Derating to max. 1000 W output power
▪
Below approx. 90 V
AC
: Shutdown of the DC output
