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4 Using the Regenerative Power System
current limit), or LIM– (negative current limit) status flag is set to indicate that a current limit has been
reached. These conditions are annunciated by CL+ or CL- on the front panel.
As shown by the vertical portions of the load line, the output voltage may continue to increase in the
positive direction or decrease in the negative direction as current is forced into or pulled out of the
unit. When the output voltage exceeds the over-voltage protection setting, the output will shut down,
the output relays will open, and the OV status bit will be set.
Current Priority
In current priority mode, the output is controlled by a bi-polar constant current feedback loop, which
maintains the output source or sink current at its programmed setting. The output current remains at
its programmed setting, provided the load voltage remains within the voltage limit setting. Current
priority mode is best suited for use with batteries, power supplies, large charged capacitors, and loads
that are sensitive to current overshoots. It minimizes current overshoots during programming, turn-on,
and turn-off transitions and seamlessly transitions between positive and negative currents.
In current priority mode, the output current should be programmed to the desired positive or negative
value. A positive voltage limit value should also be set. The voltage limit should always be set to a value
that is greater than the actual output voltage requirement of the external load. The following figure
shows the current priority operating locus of the output. The area in the white quadrants shows the
output as a source (sourcing power). The area in the shaded quadrants shows the output as a load
(sinking power).
The heavy solid line illustrates the locus of possible operating points as a function of the output load.
As shown by the vertical portion of the line, the output current remains regulated at its programmed
setting as long as the output voltage remains within its limit setting. A CC (constant current) status flag
indicates that the output current is being regulated and the output voltage is within its limit settings.
Note that when the output voltage reaches the voltage limit, the unit no longer operates in constant
current mode and the output current is no longer held constant. Instead, the power supply will now
regulate the output voltage at its voltage limit setting. A LIM+ (positive voltage limit) status flag is set
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Keysight RP7900 Series Operating and Service Guide
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