6RL SERIES OPERATION MANUAL
SECTION 7: REMOTE PROGRAMMING
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2018 by Adaptive Power Systems, Inc. (APS) • All Rights Reserved • No reproduction without written authorization from APS.
6RL Series Regenerative DC Load Operation Manual
Page 119 of 204
tolerance (or error). If you would measure the actual output voltage with an external multi-
meter and it would read 24.03 V and you would want to have closer to the desired 24 V, the
software could adjust the set value down by 30 mV (one step) or use the minimum step
width of ~3 mV to approach the target voltage in several steps.
7.4
Function Generator Minimum Slope
When programming the arbitrary generator, no matter what digital interface is used, the
unit may return errors related to the values in the sequence points. Besides obvious errors
like "value out of range", there is also a minimum slope to respect.
All sequence points have an AC part, which is only used to generate sine waves, and a DC
part with a start and value. When start and end value are different, a slope is generated.
This is normal in functions for ramp, triangle and trapezoid.
That slope (ΔU/t or ΔI/t) must fulfil a specific minimum value. In order to check if a certain
rise/fall over time is feasible, the minimum slope should be calculated for the rated values
of your particular unit.
Formula: min. slope = 0.000725 * rated voltage or current ÷ s.
In relation to the parameters you set up for a sequence point, the unit calculates the slope
in the sequence point from "Start value of DC part", "End value of DC part" and "Sequence
time" and compares it to the min. slope.
Example: For a 6Rl Load with 500 V and 30 A rating in CC Mode. A rising ramp on the current
will be generated. The min. slope calculates as: ΔI/t = 0.000725 * 30 A = 21.75 mA/s. If you
wanted to do ramp of 0-20 A in 5 s, the slope would be 4 A/s, which is OK and doable.
However, the same 0-20 A over 20 minutes is not possible and would be rejected by the
unit.
The max. time for a certain ΔU or ΔI can be calculated: t
Max
= ΔU or ΔI ÷ min. slope. For the
above example with 0-20 A we get a t
Max
= 20 A / 0.02175 A/s = ~919 seconds.
Conclusion: long-time ramps over many minutes or even hours cannot be achieved using the
function generator, but by using an alternative method, which is setting a certain number of
steps over time using a PC software.
Here the effective resolution comes into play. The DC load from the example above could be
a 6RL03-170-80-2 with a programmable resolution of 52428 steps and an effective
resolution of 26214 steps. Let's focus on the 26214. It represents 0-100% = 0-170 A when
working on the current. For 0-113 A it would then be 17476 steps. If you wanted to generate
the 0-113 A ramp over 10 hours, you could set a new value every 10 h / 17476 = ~2 seconds,
while the value increases with every step by 133 A / 17476 = ~6.48 mA.
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