© EPS Stromversorgung in 2022, this information is subject to change without notice
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30000800_manual_psb_10000_4u_30kw_en_04
3.3.3
Power regulation / constant power / power limiting
Power regulation, also known as power limiting or constant power (
CP
), keeps
the DC power constant if the current flowing to the load (source mode) resp.
the current from the source (sink mode) in relation to the voltage reaches the
adjusted limit according to P = U * I (sink mode) resp. P = U² / R (source mode).
In source mode, the power limiter then regulates 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 low-
er voltages higher current can flow and vice versa, always in order to maintain
constant power within the range P
N
(see diagram to the right).
While the DC power stage is switched on and constant power mode is active,
the condition “CP mode active” will be indicated on the graphics display by the
abbreviation
CP
, as well stored as status which can also be read as a status
message via digital interface.
Figure 15 - Power range of kW models
Figure 16 - Power range of the 10 kW model
3.3.3.1
Power derating (only 30 kW models)
As from production date of approx. 02/2022 all models can also operate on a three-phase supply of 208 V (USA, Japan).
In order to limit the AC current when running on this low input voltage, the 30 kW models switch to a derating mode which
reduces the available DC power to 18 kW. The switchover is determined once when the device is powered and depends on
the currently present AC supply voltage. It means that it cannot switch back and forth between derated and underated mode
during operation. The full power is thus only available with AC voltages from 380 V or higher.
Once derated, the device would show a permanent information in the display and all values related to the power are reduced
in their adjustment range. This also applies to master-slave operation of derated units.
3.3.4
Internal resistance regulation (source mode)
Internal resistance control (abbr. CR) of power supplies is the simulation of a virtual internal resistor which is in series to the
voltage source and thus also in series to the load. According to Ohm’s law, this causes a voltage drop, which will result in a
difference between adjusted output voltage and actual output voltage. This will work in constant current mode as well as in
constant power mode, but here the output voltage will differ even more from the adjusted voltage, because then constant
voltage is not active.
The voltage setting in dependency of the resistance set value and the output current is done by calculation of the microcon-
troller and thus will be slower the other controllers inside the control circuit. Clarification:
U
Act
= U
Set
- I
Act
* R
Set
P
Set
, I
Set
P
Ri
= (U
Set
- U
Act
) * I
Act
With resistance mode being activated the function generator will be unavailable and the actual power value
provided by the device does not include the simulated power dissipation of Ri.