Danfoss VLT Midi Drive FC 280

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.
130BD974.10
L2 92
L1 91
L3 93
M
U 96
V 97
W 98
RFI switch
Inrush
R+
82
Load sharing -
88(-)
R-
81
Brake resistor
Load sharing +
89(+)
Illustration 2.9 Control Diagram
2.3.3
Control Structure in VVC
+
+
_
+
_
S
S
Cong. mode
Ref.
Process
P 1-00
High
+f max.
Low
-f max.
P 4-12
Motor speed
low limit (Hz)
P 4-14
Motor speed
high limit (Hz)
Motor
controller
Ramp
Speed
PID
P 7-20 Process feedback
1 source
P 7-22 Process feedback
2 source
P 7-00 Speed PID
feedback source
P 1-00
Cong. mode
P 4-19
Max. output freq.
-f max.
Motor
controller
P 4-19
Max. output freq.
+f max.
P 3-**
P 7-0*
130BD371.10
Illustration 2.10 Control Structure in VVC
+
Open-loop Congurations and Closed-loop Congurations
In the conguration shown in Illustration 2.10, parameter 1-01 Motor Control Principle is set to [1] VVC
+
and
parameter 1-00 Conguration Mode is set to [0] Speed open loop. The resulting reference from the reference handling system
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