Automatic Restart; Flying Start; Full Torque At Reduced Speed; Frequency Bypass - Danfoss VLT AQUA Drive FC 202 Design Manual

Product Overview
Use the three additional and independent controllers for
controlling other process equipment, such as chemical feed
pumps, valve control or for aeration with different levels.

2.6.5 Automatic Restart

The adjustable frequency drive can be programmed to
automatically restart the motor after a minor trip, such as
momentary power loss or fluctuation. This feature
eliminates the need for manual resetting and enhances
automated operation for remotely controlled systems. The
number of restart attempts as well as the duration
between attempts can be limited.

2.6.6 Flying Start

Flying start allows the adjustable frequency drive to
synchronize with an operating motor rotating at up to full
speed, in either direction. This prevents trips due to
overcurrent draw. It minimizes mechanical stress to the
system since the motor receives no abrupt change in
speed when the adjustable frequency drive starts.

2.6.7 Full Torque at Reduced Speed

The adjustable frequency 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 is unlike
variable torque drives that provide reduced motor torque
at low speed, or constant torque drives that provide excess
voltage, heat, and motor noise at less than full speed.

2.6.8 Frequency Bypass

In some applications, the system may have operational
speeds that create a mechanical resonance. This can
generate excessive noise and possibly damage mechanical
components in the system. The adjustable frequency drive
has four programmable bypass-frequency bandwidths.
These allow the motor to step over speeds that induce
system resonance.

2.6.9 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 a cold start.
This can eliminate the need for a space heater.
MG20N622
Design Guide

2.6.10 Four Programmable Set-ups

The adjustable frequency drive has four 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 active set-up is displayed
on the LCP.
Set-up data can be copied from adjustable frequency drive
to adjustable frequency drive by downloading the
information from the removable LCP.

2.6.11 Dynamic Braking

Dynamic Brake is established by:
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2.6.12 DC Braking

Some applications may require braking a motor to slow or
stop it. Applying DC current to the motor brakes the motor
and can eliminate the need for a separate motor brake. DC
braking can be set to activate at a predetermined
frequency or upon receiving a signal. The rate of braking
can also be programmed.

2.6.13 Sleep Mode

Sleep mode automatically stops the motor when demand
is low for a specified period of time. When the system
demand increases, the drive restarts the motor. Sleep
mode provides energy savings and reduces motor wear.
Unlike a setback clock, the drive is always available to run
when the preset wake-up demand is reached.

2.6.14 Run Permissive

The drive can wait for a remote system ready signal before
starting. When this feature is active, the drive remains
stopped until receiving permission to start. Run permissive
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Resistor brake
A brake IGBT keeps the overvoltage under a
certain threshold by directing the brake energy
from the motor to the connected brake resistor
(2-10 Brake Function = [1]).
AC brake
The brake energy is distributed in the motor by
changing the loss conditions in the motor. The
AC brake function cannot be used in applications
with high cycling frequency since this overheats
the motor (2-10 Brake Function = [2]).
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