100
Speed Reference
Figure 17 Trim
The source of the trim signal is selected through [Trim In Sel], parameter 117. All
selections for [Speed Ref A] and [Speed Ref B] are also valid choices for a trim
source. In addition, [Trim % Setpoint], parameter 116 is also available as a trim
source.
[Trim Out Select], parameter 118 configures which speed reference(s) will be
trimmed and whether the trim signal is either added as an absolute fixed amount
over the speed range, or a percent of the speed reference:
•
Bit 0, “Trim Ref A” 0 = not trimmed, 1 = trimmed
•
Bit 1, “Trim Ref B” 0 = not trimmed, 1 = trimmed
•
Bit 2, “Add or %”
0 = A specific value of the trim source provides an absolute amount of trim
(equal to a percent of [Maximum Speed]) over entire speed range.
1 = A specific value of the trim source provides a percent amount of trim (equal
to a percent of the speed reference) over the entire speed range.
If the trim source is an analog input, [Trim Hi] and [Trim Lo], parameters 119 &
120 scale the trim signal in units of either Hz or %, dependent on whether or not
“Add” or “%” mode is selected.
If the trim source is [Trim % Setpoint], its units (Hz or %) are also dependent on
whether or not “Add” or “%” mode is selected.
Example 1: “Percent” mode:
−
[Maximum Speed] = 60
−
[Trim In Select} = 2 “Analog In 2"
−
[Trim Out Select], bit 0 “Speed Ref A” = 1
−
[Trim Out Select], bit 2 “Add or %” = 1 (% mode)
If the speed reference = 20 Hz, and Analog Input 2 = 1V, the resulting trim will be 20 Hz x 10% = 2.0
Hz, which when added to the speed reference is 20Hz. As the speed reference changes, the absolute
amount of trim also changes since it is a percent of the speed reference For example, if the speed
reference changes to 40 Hz, the amount of trim added is 40 Hz x 10% = 4.0 Hz, and so on.
Example 2: “Add” mode:
−
[Maximum Speed] = 60
−
[Trim In Select] = 2 “Analog In 2"
−
[Trim Out Select], bit 0 “Speed Ref A” = 1
−
[Trim Out Select], bit 2 “Add or % Ref” = 0 (Add mode)
If the speed reference = 20 Hz, and Analog Input 2 = 10V, the resulting trim will be 60 Hz x 20% = 12
Hz, which is added to the speed reference even as the speed reference changes. For example, if the
speed reference changes to 40Hz, the absolute amount of trim added remains equal to 60 Hz x 10% =
4.0 Hz, and so on. In this case a different absolute amount of trim would require a change at analog
input 2.
Trim Enable Select
+
+
+
+
Trimmed
Reference A
Trimmed
Reference B
Reference B
Reference A
Trim
A
B
Both
None