User manual

Page 40
PSI 9000 DT Series
www.elektroautomatik.de
[e-mail]
EA Elektro-Automatik GmbH
Helmholtzstr. 31-33 • 41747 Viersen
Germany
Fon: +49 2162 / 3785-0
Fax: +49 2162 / 16230
3. Operation and application
3.1 Personal safety
• In order to guarantee safety when using the device, it is essential that only persons operate
the device who are fully acquainted and trained in the required safety measures to be taken
when working with dangerous electrical voltages
• For models which can generate a voltage which is dangerous by contact, or is connected to
such, all cables with lugs have to be crimped with insulated lugs. If necessary, install additional
measures for protection against physical contact, such as a cover
• WhenevertheloadandDCoutputarebeingre-congured,thedeviceshouldbeswitchedoff
completely, not only the DC output!
3.2 Operating modes
A power supply is internally controlled by different control or regulation circuits, which shall bring voltage, current
and power to the adjusted values and hold them constant, if possible. These circuits follow typical laws of control
systems engineering, resulting in different operating modes. Every operating mode has its own characteristics
which is explained below in short form.
• Unloaded operation is not considered as a normal operation mode and can thus lead to false
measurements, for example when calibrating the device
• The optimal working point of the device is between 50% and 100% voltage and current
• It is recommended to not run the device below 10% voltage and current, in order to make
sure technical values like ripple and transient times can be met
3.2.1 Voltage regulation / Constant voltage
Voltage regulation is also called constant voltage operation (CV).
The DC output voltage of a power supply is held constant on the adjusted value, unless the output current or the
output power according to P = U
OUT
* I
OUT
reaches the adjusted current or power limit. In both cases the device
willautomaticallychangetoconstantcurrentorconstantpoweroperation,whateveroccursrst.Thentheoutput
voltage can’t be held constant anymore and will sink to a value resulting from Ohm’s law.
While the DC output is switched on and constant voltage mode is active, then the condition “CV mode active” will
be indicated on the graphic display by the abbreviation CV 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.
3.2.1.1 Transient time after load step
For constant voltage mode (CV), the technical date “Settling time after load step” (see 1.8.3)denesatimethatis
required by the internal voltage regulator of the device to settle the output voltage after a load step. Negative load
steps, i.e. high load to lower load, will cause the output voltage to overshoot for a short time until compensated by
the voltage regulator. The same occurs with a positive load step, i.e. low load to high load. There the output col-
lapses for a moment. The amplitude of the overshoot resp. collapse depends on the device model, the currently
adjustedoutputvoltageandthecapacityontheDCoutputandcanthusnotbestatedwithaspecicvalue.
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.