Normal operation: Ramping
The DC level during [4] Kinetic backup equals parameter 14-11 Mains Fault Voltage Level x 1.35. If the mains does
not return, U
DC
is maintained as long as possible by ramping the speed down towards 0 RPM. Finally, the drive
coasts. If the mains returns while in kinetic back-up mode, U
DC
increases above parameter 14-11 Mains Fault
Voltage Level x 1.35. This is detected in 1 of the following ways:
If U
DC
> parameter 14-11 Mains Fault Voltage Level x 1.35 x 1.05.
If the speed is above the reference. This is relevant if the mains comes back at a lower level than before, for
example parameter 14-11 Mains Fault Voltage Level x 1.35 x 1.02. This does not fulfill the criterion in point 1,
and the drive tries to reduce U
DC
to parameter 14-11 Mains Fault Voltage Level x 1.35 by increasing the
speed. This cannot be done as the mains cannot be lowered.
If running mechanically. The same mechanism as in point 2 applies, but the inertia prevents the speed from
going above the reference speed. This leads to the motor running mechanically until the speed is above
the reference speed and the situation in point 2 occurs. Instead of waiting for that criterion, point 3 is intro-
duced.
The difference between kinetic back-up with and without trip is that the latter always ramps down to 0 RPM
and trips, regardless of whether mains returns or not. The function does not detect if mains returns. This is the
reason for the relatively high level on the DC link during ramp-down.
SP-11*1.35
Ref
790 V
0
A B C D
e30bc920.10
U
DC
[V]
n [RPM]
t [S]
U
DC
t [S]
Illustration 84: Kinetic Back-up Trip
Kin.
back-
up, trip
w re-
covery
This option is valid in VVC+ only. Kinetic back-up with recovery combines the features of kinetic back-up and
kinetic back-up with trip. This feature makes it possible to select between kinetic back-up and kinetic back-up
with trip, based on a recovery speed, configurable in parameter 14-15 Kin. Back-up Trip Recovery Level. If mains
does not return, the drive ramps down to 0 RPM and trips. If mains returns while in kinetic back-up at a speed
above the value in parameter 14-15 Kin. Back-up Trip Recovery Level, normal operation is resumed. This is equal
to [4] Kinetic Back-up. The DC level during [7] Kin. back-up, trip w recovery is parameter 14-11 Mains Fault Voltage
Level x 1.35.
Ref
U
DC
SP-15
A B C D EA
e30bc922.10
U
DC
[V]
n [RPM]
t [S]
t [S]
SP-11*1.35
Illustration 85: Kinetic Back-up Trip w/Recovery, Mains Returns Above Parameter 14-15 Kin. Back-up Trip Recovery Level
AU275636650261en-000101 / 130R0334 | 455Danfoss A/S © 2022.12
Parameter Descriptions
VLT AutomationDrive FC 301/302
Programming Guide
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