Danfoss VLT Midi Drive FC 280 Programming Guide

14-10 Mains Failure
Option: Function:
[2] Ctrl.
ramp-
down,
trip
This selection is similar to selection [1] Ctrl. ramp-
down, except that in [2] Ctrl. ramp-down, trip a
reset is necessary for starting up after power-up.
[3] Coasting Centrifuges can run for an hour without power
supply. In those situations, it is possible to select a
coast function at mains interruption, together with
a ying start, which occurs when the mains is
restored.
[4] Kinetic
back-up
Kinetic back-up ensures that the frequency
converter keeps running as long as there is energy
in the system due to the inertia from motor and
load. This is done by converting the mechanical
energy to the DC-link and thereby maintaining
control of the frequency converter and motor. This
can extend the controlled operation, depending
on the inertia in the system. For fans, it is typically
several seconds, for pumps up to 2 s and for
compressors only for a fraction of a second. Many
industry applications can extend controlled
operation for many seconds, which is often
enough time for the mains to return.
130BC918.10
U
14-11*1.35
Ref
n [RPM]
t [S]
A B C
D
E A
DC
U
DC
[V]
t [S]
A Normal operation
B Mains failure
C Kinetic back-up
D Mains return
E Normal operation: Ramping
Illustration 4.17 Kinetic Back-up
The DC-level during [4] Kinetic back-up is
parameter 14-11 Mains Voltage at Mains Faultx1.35.
If the mains does not return, U
DC
is maintained as
long as possible by ramping the speed down
towards 0 RPM. Finally, the frequency converter
coasts.
If mains returns while in kinetic back-up, U
DC
increases above parameter 14-11 Mains Voltage at
Mains Faultx1.35. This is detected in 1 of the
following ways:
•
If U
DC
> parameter 14-11 Mains Voltage at
Mains Faultx1.35x1.05
•
If the speed is above the reference. This
is relevant if mains comes back at a
lower level than before, for example,
14-10 Mains Failure
Option: Function:
parameter 14-11 Mains Voltage at Mains
Faultx1.35x1.02. This does not fulll the
criterion above, and the frequency
converter tries to reduce U
DC
to
parameter 14-11 Mains Voltage at Mains
Faultx1.35 by increasing the speed. This
does not succeed as mains cannot be
lowered.
•
If running motoric. The same mechanism
as in the previous point, but where the
inertia prevents that the speed goes
above the reference speed. This leads to
the motor running motoric until the
speed is above the reference speed, and
the above situation occurs. Instead of
waiting for that, the present criterion is
introduced.
[5] Kinetic
back-up,
trip
The dierence between kinetic back-up with and
without trip is that the latter always ramps down
to 0 RPM and trips, regardless of whether mains
return or not.
The function is made so that it does not even
detect if mains return, this is the reason for the
relatively high level on the DC-link during ramp
down.
14-11*1.35
Ref
790 V
0
A B C D
130BC920.10
U
n [RPM]
t [S]
DC
U
DC
[V]
t [S]
A Normal operation
B Mains failure
C Kinetic back-up
D Trip
Illustration 4.18 Kinetic Back-up Trip
[6] Alarm
[7] Kin.
back-up,
trip w
recovery
Parameter Descriptions
VLT
®
Midi Drive FC 280
92 Danfoss A/S © 12/2015 All rights reserved. MG07C102
44

Danfoss VLT Midi Drive FC 280 Specifications

General

Brand	Danfoss
Model	VLT Midi Drive FC 280
Category	DC Drives
Language	English