User manual

Page 25
EA Elektro-Automatik GmbH
Helmholtzstr. 31-33 • 41747 Viersen
Germany
Fon: +49 2162 / 3785-0
Fax: +49 2162 / 16230
www.elektroautomatik.de
[e-mail]
ELR/ELM 5000 Series
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 accept dangerous voltages, the included DC terminal cover or an equivalent
must always be used
• WhenevertheDCinputisbeingre-congured,thedeviceshouldbedisconnectedfromthe
mains, not only switched off on the DC input! Also switch off or even disconnect the source!
3.2 Regulation modes
An electronic load 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 resp. regulation modes. Every regulation mode has its own
characteristics which is explained below in short form.
3.2.1 Voltage regulation / Constant voltage
Constant voltage operation (CV) or voltage regulation is a subordinate operating mode of electronic loads. In nor-
mal operation, a voltage source is connected to electronic load, which represents a certain input voltage for the
load. If the set value for the voltage in constant voltage operation is higher than the actual voltage of the source,
the value cannot be reached. The load will then take no current from the source. If the voltage set value is lower
than the input voltage then the load will attempt to drain enough current from the source to achieve the desired
voltage level. If the resulting current exceeds the maximum possible or adjusted current value or the total power
according to P = U
IN
* I
IN
is reached, the load will automatically switch to constant current or constant power opera-
tion,whatevercomesrst.Thentheadjustedinputvoltagecannolongerbeachieved.
While the DC input is switched on and constant voltage mode is active, then the condition “CV mode active” will be
shown on the graphics display by the abbreviation CV and stored as internal status which can be read via digital
interface.
3.2.1.1 Minimum voltage for maximum current
Due to technical reasons, all models in this series have a minimum internal resistance that makes the unit to be
provided with a minimum input voltage (U
MIN
) in order to be able to draw the full current (I
MAX
). This minimum input
voltagevariesfrommodeltomodel.ThetechnicalspecicationslistU
MIN
for every model. If less voltage than U
MIN
is supplied, the load proportionally draws less current than adjusted.
3.2.2 Current regulation / constant current / current limitation
Current regulation is also known as current limitation or constant current mode (CC) and is fundamental to the
normal operation of an electronic load. The DC input current is held at a predetermined level by varying the internal
resistanceaccordingtoOhm’slawR=U/Isuchthat,basedontheinputvoltage,aconstantcurrentows.Once
the current has reached the adjusted value, the device automatically switches to constant current mode. However,
if the power consumption reaches the adjusted power level, the device will automatically switch to power limitation
and adjust the input current according to I
MAX
= P
SET
/ U
IN
, even if the maximum current set value is higher. The
current set value, as determined by the user, is always and only an upper limit.
While the DC input is switched on and constant current mode is active, the condition “CC mode active” will be shown
on the graphics display by the abbreviation CC and stored as internal status which can be read via digital interface.