User Manual

Page 29
EA Elektro-Automatik GmbH
Helmholtzstr. 31-33 • 41747 Viersen
Germany
Fon: +49 2162 / 3785-0
Fax: +49 2162 / 16230
www.elektroautomatik.de
[e-mail]
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owing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ows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
Some models of series PS 9000 1U require a so-called thermal derating in certain situations where the device
could overheat internally, possibly in connection with high ambient temperature and when the device is running
under full load (100% power, 100% current). This derating avoids early temperature depending shutdown.
Generally,allmodelsofseriesPS90001Uarespeciedforanambienttemperatureof0...50°C.Somemodels
cannot provide full power at full current starting from ambient temperatures of ~ 42 °C while they can provide, for
example, full power at half of the max. current. In order to prevent the device from switching off because of over-
temperature, it is recommend to apply a thermal derating which is done by the user in form of reducing the power
consumption by a certain amount of Watts per degree Celsius.
Models which are affected by this method of thermal derating:
• PS 9200-50 1U (200 V, 50 A, 3 kW)