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Chapter 5 Signal Mapping Innovation Series Medium Voltage GP Type - G Drives GEH-6385
Application of Feedback Signals
In most control systems the LAN (Genius, Profibus-DP, and such) operates
asynchronous with th e execution of control logic. Two sit uations can occur:
• Under Sampling - If the control logic sweep r ate is slower than the LAN sweep
rate, certain sampl es of feedback signals from the dri ve are not seen by the
control logic.
• Over Sampling - If the control logic sweep rate is faster than th e LAN sweep
rate, certain feedback signal samples from the drive are s een multiple times by
the control logic.
To ad dress the under sa mpling problem, signal conditi oning is provided f or
dedicated analog feedback channels in the form of sequ ential averaging. Feedback
signals are comprised of a series of short-term averag es of the source signal. The
parameter LAN fbk avg time con figures the averaging period ; updates to the feedback
signal map ar e performed coher ently.
Note that when an integer relationship exists between LAN frame time and LAN fbk
avg time, then the frame and feedback aver aging periods are synchron ized to the
extent possible. This synchronization is optimal for synchronous LAN interfaces,
such as those provided by the ISBus.
Variable Maps
This section defines the signal maps for the ACMVAC4-G (General Industries)
pattern. Th e following table s provide:
• Standard 32-bit SPFP maps
• 20-character user nam es and 12-character symbolic nam es
• Units or scal e groups (as approp riate)