Danfoss VLT AutomationDrive FC 360 Programming Manual page 103

Parameter Descriptions
14-10 Mains Failure
Option: Function:
parameter 3-81 Quick Stop Ramp Time. This
selection is useful in pump applications, where the
inertia is low and the friction is high. When mains
is restored, the output frequency ramps the motor
up to the reference speed (if the mains
interruption is prolonged, the controlled ramp
down might take down the output frequency to 0
RPM, and when the mains is restored, the
application is ramped up from 0 RPM to the
previous reference speed via the normal ramp up).
If the energy in the DC-link disappears before the
motor is ramped to 0, the motor is coasted.
[2] Ctrl. This selection is similar to selection [1] Ctrl. ramp-
ramp- down, except that in [2] Ctrl. ramp-down, trip a
down, reset is necessary for starting up after power-up.
trip
[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 flying start, which occurs when the mains is
restored.
[4] Kinetic Kinetic back-up ensures that the frequency
back-up 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.
U [V]
DC
U
DC
14-11*1.35
n [RPM]
Ref
A Normal operation
B Mains failure
C Kinetic back-up
D Mains return
E Normal operation: Ramping
Illustration 4.29 Kinetic Back-up
The DC-level during [4] Kinetic back-up is
parameter 14-11 Mains Fault Voltage Level x 1.35.
MG06C702
Programming Guide
A B C D E A
t [S]
t [S]
Danfoss A/S © 06/2017 All rights reserved.
14-10 Mains Failure
Option: Function:
If the mains does not return, U
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
increases above parameter 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
DC
Voltage Level x 1.35 x 1.05
•
If the speed is above the reference. This
is relevant if 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 above, and the frequency
converter tries to reduce U
parameter 14-11 Mains Fault Voltage Level
x 1.35 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 the speed from going
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 The difference between kinetic back-up with and
back-up, without trip is that the latter always ramps down
trip 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.
U [V]
DC
790 V
U DC
14-11*1.35
n [RPM]
Ref
0
A Normal operation
B Mains failure
C Kinetic back-up
D Trip
Illustration 4.30 Kinetic Back-up Trip
is maintained as
DC
DC
to
DC
A B C D
t [S]
t [S]
101
4 4