Dead Band Around Zero - Danfoss VLT AutomationDrive FC 301 Series Design Manual

Basic Operating Principles

3.7.5 Dead Band Around Zero

In some cases, the reference (in rare cases also the
feedback) should have a dead band around zero (i.e., to
make sure the machine is stopped when the reference is
"near zero").
To activate the dead band and to set the amount of
dead band, set the following:
•
Either Minimum Reference Value or Maximum
Reference Value must be zero. In other words,
Either P1 or P2 must be on the X-axis in
Figure 3.19.
•
And both points defining the scaling graph are in
the same quadrant.
The size of the dead band is defined by either P1 or P2 as
shown in Figure 3.19.
Resource output
Quadrant 2
(RPM)
High reference/feedback
1500
value
Low reference/feedback
0 P1
value
-10 -6 -1 1
Terminal X
low
-1500
Quadrant 3
Figure 3.19 Dead Band
MG33BF22
Design Guide
Quadrant 2
High reference/feedback
value
-10
Quadrant 3
Figure 3.20 Reverse Dead Band
Quadrant 1
Thus a reference endpoint of P1 = (0 V, 0 RPM) does not
result in any dead band, but a reference endpoint of, e.g.,
P1 = (1 V, 0 RPM) results in a -1 V to +1 V dead band in
P2
this case, provided that the end point P2 is placed in
either Quadrant 1 or Quadrant 4.
Resource
input
(V)
6 10
Terminal X
high
Quadrant 4
Rev. 2014-04-04 All rights reserved.
Resource output
(RPM)
1500
Low reference/feedback
P1
value
P2 0
-6 -1 1
Terminal X Terminal X
low high
-1500
Quadrant 1
3
Resource
input
(V)
6 10
Quadrant 4
35
3