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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-configured, you must switch off or even better, disconnect
the source!
3.2
Operating 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 modes. Every operating 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
normal operation, a voltage source is connected to electronic the load, representing a certain input voltage. 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 sink no current from the source. If the voltage set value is lower than the
input voltage then the load will attempt to sink enough current from the source to achieve the desired voltage level.
If the resulting current reaches the adjusted current set value or the actual power according to P = U
the adjusted power set value, the load will automatically switch to constant current or constant power operation,
depending on what occurs first. 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, as well it will be passed as a signal to the analog interface
(depending on the settings) and stored as internal status which can be read via digital interface.
3.2.1.1
Speed of the voltage controller
The internal voltage controller can be switched between "Slow" and "Fast" (see „3.4.3.1. Menu "General Settings"").
Factory default value is "Slow". Which of both is the best setting depends on the actual situation in which the device
is going to be operated, but primarily it depends on the type of voltage source. An active, regulated source such as a
switching mode power supply has its own voltage control circuit which works concurrently to the load's circuit. Both
might work against each other and lead to oscillation. If this occurs it's recommended to set the controller speed to
"Slow".
In other situations, e.g. operating the function generator and applying various functions to the load's input voltage
and setting of small time increments, it might be necessary to set the voltage controller to "Fast" in order to achieve
the expected results.
3.2.1.2
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
supplied with a minimum input voltage (U
to be able to draw the full current (I
input voltage varies from model to model and is listed in
the technical specifications. If less voltage than U
supplied, the load proportionally draws less current than
adjusted, which can be calculated easily.
See principle view to the right.
EA Elektro-Automatik GmbH
Helmholtzstr. 31-37 • 41747 Viersen
Germany
U(V)
) in order
MIN
). This minimum
MAX
is
MIN
Fon: +49 2162 / 3785-0
Fax: +49 2162 / 16230
EL 9000 B Series
Umin
I
Imax
www.elektroautomatik.de
ea1974@elektroautomatik.de
reaches
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IN
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