Danfoss VLT AutomationDrive FC 361 Series Design Manual page 67

Basic Operating Principles ...
8.2.5 Open-loop Control Structure
In open-loop mode, the drive uses 1 or more references (local or remote) to control the speed or torque of the motor. There
are 2 types of open-loop control:
•
Speed control. No feedback from the motor.
•
Torque control. Used in VVC
limited. Open-loop torque function works only in 1 speed direction. The torque is calculated based on current
measurement within the drive. See chapter 9 Application Examples.
In the configuration shown in Illustration 8.6, the drive operates in open-loop mode. It receives input from either the LCP
(hand-on mode) or via a remote signal (auto-on mode).
The signal (speed reference) is received and conditioned with the following:
•
Programmed minimum and maximum motor speed limits (in RPM and Hz).
•
Ramp-up and ramp-down times.
•
Motor rotation direction.
The reference is then passed on to control the motor.
Reference
handling
Remote
reference
Auto mode
Linked to hand/auto
Hand mode
Local
reference
scaled to
RPM or Hz
LCP Hand on,
o and auto
on keys
Illustration 8.6 Block Diagram of an Open-loop Control Structure
MG06K102
Design Guide
+
mode. The function is used in mechanically robust applications, but its accuracy is
P 4-13
Motor speed
high limit [RPM]
P 4-14
Motor speed
high limit [Hz]
Remote
Reference
Local
P 4-11
Motor speed
low limit [RPM]
P 3-13
Reference P 4-12
site Motor speed
low limit [Hz]
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100%
P 3-4* Ramp 1
P 3-5* Ramp 2
0%
Ramp
100%
-100%
8
To motor
control
P 4-10
Motor speed
direction
65
8