User Manual

Page 35
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 9000 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 source and DC input are being re-congured, the device should be disconnected
from the mains, not only the DC input switched off!
3.2 Operating modes
3.2.1 Voltage regulation / Constant voltage
Constant voltage operation (CV) or voltage regulation is a subsidiary operating mode. In normal operation, a volt-
age source is connected to the input of an 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, then this
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 load the source with enough current (voltage loss across the internal
resistance of the source) to achieve the target voltage. If this current exceeds the set maximum current value or
that of the assimilated power according to P = U
IN
* I
IN
then the load will switch automatically to constant current
or constant power operation as appropriate. The input voltage can then no longer achieve the intended set value
but rather will rise to a value higher than adjusted.
If the DC input is switched on and constant voltage mode is active, then the condition “CV mode active” will be
shown 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 Speed of the voltage regulator
The internal voltage regulator can be switched between “slow” and “fast” (see „3.3.3.1. Menu “General Settings”“).
Factory default value is “slow”. Which setting should be used depends on the actual situation in which the load is
to be applied, but primarily from the type of voltage source. An active, regulated source such as a switching mode
power supply has its own voltage regulator which works concurrently with the load. The two can then work against
each other and lead to oscillation in the input regulation behaviour. If this occurs it is recommended to set the volt-
age regulator to “slow”. In other situations, e.g. operating the function generator and applying the various functions
to the load input voltage and setting of small time increments, it may be necessary to set the voltage regulator to
“fast” in order to achieve the expected results.
3.2.2 Current regulation / constant current / current limitation
Current regulation is also known as current limiting or constant current mode (CC) and is fundamental to the nor-
mal operation of an electronic load. The DC input current is held by the electronic load at a predetermined level by
varying the internal resistance of the load 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 switches automatically to
constant current mode. If, however, the power consumption reaches the adjusted power set value, the device will
switch automatically to power limiting and sets the input 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 input is switched on and constant current mode is active, then the condition “CC mode active” will be
shown 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.