Danfoss FC 300 Programming Manual page 136

Parameter Descriptions
14-10 Mains Failure
Par. 14-10 Mains Failure is typically used where very short mains
interruptions (voltage dips) are present. At 100% load and a short
voltage interruption, the DC voltage on the main capacitors drops
quickly. For larger drives it only takes a few milliseconds before the
3 3 DC level is down to about 373 V DC and the main IGBT cuts off and
looses the control over the motor. When the mains is restored, and
the IGBT starts again, the output frequency and voltage vector
does not correspond to the speed/frequency of the motor, and the
result is normally an overvoltage or overcurrent, mostly resulting in
a trip lock. Par. 14-10 Mains Failure can be programmed to avoid
this situation.
Option:
[0] No function
*
[1] Ctrl. ramp-
down
[2] Ctrl. ramp-
down, trip
[3] Coasting
[4] Kinetic back-
up
136
FC 300 Programming Guide
Function:
This selection does not present a
danger to the frequency converter, but
a trip lock would normally be the result
of the short voltage interruptions.
This selection will keep the output
frequency following the motor speed.
The IGBT will not loose the connection
to the motor, but will follow the speed
down. This is particularly useful in
pump applications, where the inertia is
low and the friction is high. When the
mains is restored, the output frequency
will ramp the motor up to the reference
speed (if the mains interruption is
prolonged, the controlled ramp down
might take the output frequency all the
way down 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).
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.
Kinetic back up will maintain the DC
level as long as possible, by converting
the mechanical energy from the motor
to the DC level supply. Fans normally
can extend the mains interruptions for
several seconds. Pumps can normally
only extend the interruptions for 1-2
MG.33.M9.02 - VLT
14-10 Mains Failure
Par. 14-10 Mains Failure is typically used where very short mains
interruptions (voltage dips) are present. At 100% load and a short
voltage interruption, the DC voltage on the main capacitors drops
quickly. For larger drives it only takes a few milliseconds before the
DC level is down to about 373 V DC and the main IGBT cuts off and
looses the control over the motor. When the mains is restored, and
the IGBT starts again, the output frequency and voltage vector
does not correspond to the speed/frequency of the motor, and the
result is normally an overvoltage or overcurrent, mostly resulting in
a trip lock. Par. 14-10 Mains Failure can be programmed to avoid
this situation.
Option:
[5] Kinetic back-
up, trip
[6] Alarm
14-11 Mains Voltage at Mains Fault
Range:
Application [180 - This parameter defines the threshold
depend- 600 V] voltage at which the selected function in
ent par. 14-10 Mains Failure should be activated.
*
The detection level is at a faktor sqrt(2) of
the value in 14-11.
NOTE
Note for converting between VLT
5000 and FC 300:
Even though the setting of the
Mains Voltage at Mains Fault is the
same for VLT 5000 and FC 300, the
detection level is different. Use the
following formula to obtain the
same detection level as in VLT 5000:
14-11 (VLT 5000 level) = Value used
in VLT 5000 * 1,35/sqrt(2).
14-12 Function at Mains Imbalance
Operation under severe main imbalance conditions reduces the
lifetime of the motor. Conditions are considered severe if the motor
is operated continuously near nominal load (e.g. a pump or fan
running near full speed).
Option:
[0] Trip
*
[1] Warning
[2] Disabled
®
is a registered Danfoss trademark
Function:
seconds or fractions of seconds.
Compressors only for fractions of
seconds.
Function:
Function:
Trips the frequency
converter
Issues a warning
No action