Danfoss VLT FC 102 Programming Manual page 362

Programming Guide | VLT® HVAC Drive FC 102
Option Name
[4] Kinetic back-up
362 | © 2024.10
Description
together with a flying start, which occurs when the mains is
restored.
Kinetic back-up ensures that the drive 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 maintaining control of the drive 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.
A B C
U [V]
DC
U DC
SP-11*1.35
n [RPM]
Ref
Figure 68: Kinetic Back-up
A Normal operation
C Kinetic back-up
E 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
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
14-11 Mains Fault Voltage Level x 1.35. This is detected in 1 of the
following ways:
• If U > parameter 14-11 Mains Fault Voltage Level x 1.35 x
DC
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 to parameter 14-11 Mains Fault Voltage Level x
DC
1.35 by increasing the speed. This cannot be done as the mains
cannot be lowered.
• If the motor runs mechanically. The same mechanism as in
point 2 applies, but the inertia prevents the speed from going
Parameter Descriptions
D E
A
t [S]
t [S]
B Mains failure
D Mains return
increases above parameter
DC
AU430028034214en-001901 / 130R0310
DC