5.2.5 Mains Drop-out
During a mains drop-out, the drive keeps running until the
DC-link voltage drops below the minimum stop level. The
minimum stop level is typically 15% below the lowest
rated supply voltage. The mains voltage before the drop-
out and the motor load determines how long it takes for
the drive to coast.
The drive can be
congured (parameter 14-10 Line Failure)
to dierent types of behavior during mains drop-out:
•
Trip lock once the DC link is exhausted.
•
Coast with ying start whenever mains return
(parameter 1-73 Flying Start).
•
Kinetic back-up.
•
Controlled ramp down.
Flying start
This selection makes it possible to catch a motor that is
spinning freely due to a mains drop-out. This option is
relevant for centrifuges and fans.
Kinetic back-up
This selection ensures that the drive runs as long as there
is energy in the system. For short mains drop-out, the
operation is restored after mains return, without bringing
the application to a stop or losing control at any time.
Several variants of kinetic back-up can be selected.
Congure the behavior of the drive at mains drop-out in
parameter 14-10 Line Failure and parameter 1-73 Flying Start.
5.2.6 Automatic Restart
The drive can be programmed to restart the motor
automatically after a minor trip, such as momentary power
loss or uctuation. This feature eliminates the need for
manual resetting, and enhances automated operation for
remotely controlled systems. The number of restart
attempts and the duration between attempts can be
limited.
5.2.7 Full Torque at Reduced Speed
The drive follows a variable V/Hz curve to provide full
motor torque even at reduced speeds. Full output torque
can coincide with the maximum designed operating speed
of the motor. This drive diers from variable torque drives
and constant torque drives. Variable torque drives provide
reduced motor torque at low speed. Constant torque
drives provide excess voltage, heat, and motor noise at less
than full speed.
5.2.8 Frequency Bypass
In some applications, the system can have operational
speeds that create a mechanical resonance. This
mechanical resonance can generate excessive noise and
possibly damage mechanical components in the system.
The drive has 4 programmable bypass-frequency
bandwidths. The bandwidths allow the motor to step over
speeds that induce system resonance.
5.2.9 Motor Preheat
To preheat a motor in a cold or damp environment, a small
amount of DC current can be trickled continuously into the
motor to protect it from condensation and cold starts. This
function can eliminate the need for a space heater.
5.2.10 Programmable Set-ups
The drive has 4 set-ups that can be independently
programmed. Using multi-setup, it is possible to switch
between independently programmed functions activated
by digital inputs or a serial command. Independent set-ups
are used, for example, to change references, or for day/
night or summer/winter operation, or to control multiple
motors. The LCP shows the active set-up.
Set-up data can be copied from drive to drive by
downloading the information from the removable LCP.
Product Features Design Guide
MG22B222 Danfoss A/S © 01/2018 All rights reserved. 23
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