Control Principle; Control Structure In Vvc - Danfoss VLT Midi Drive FC 280 Design Manual

Product Overview

2.3.2 Control Principle

VLT® Midi Drive FC 280 is a general-purpose frequency converter for variable speed applications. The control principle is
+
based on VVC .
FC 280 frequency converters can handle asynchronous motors and permanent magnet synchronous motors up to 22 kW
(30 hp).
The current-sensing principle in FC 280 frequency converters is based on the current measurement by a resistor in the DC
link. The ground fault protection and short circuit behavior are handled by the same resistor.
L1 91
L2 92
L3 93
Illustration 2.9 Control Diagram

2.3.3 Control Structure in VVC

P 1-00
Con g. mode
Ref.
+
Process
S
_
P 7-20 Process feedback
1 source
P 7-22 Process feedback
2 source
Illustration 2.10 Control Structure in VVC
In the configuration shown in Illustration 2.10, parameter 1-01 Motor Control Principle is set to [1] VVC
parameter 1-00 Configuration Mode is set to [0] Speed open loop. The resulting reference from the reference handling system
MG07B102
Design Guide
Load sharing +
89(+)
Inrush
RFI switch
Load sharing -
+
P 1-00
P 4-14
Con g. mode
Motor speed
high limit (Hz)
P 3-**
High
Ramp
Low
P 4-12
Motor speed
low limit (Hz)
+ Open-loop Configurations and Closed-loop Configurations
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Brake resistor
R+ R-
82 81
88(-)
P 4-19
Max. output freq.
+f max.
Motor
controller
-f max.
P 7-0*
Speed Motor
+
S
PID controller
_
P 7-00 Speed PID
feedback source
U 96
V 97
M
W 98
P 4-19
Max. output freq.
+f max.
-f max.
+
and
19
2 2