Danfoss VLT AutomationDrive FC 301 Series Design Manual page 184

Options and Accessories
11.3.3 VLT
351
NOTICE!
Terminal block X59 has fixed functionality for MCO 351.
NOTICE!
Terminal block X62 is not supported for MCO 351.
NOTICE!
Terminal block X60 is not used for MCO 351.
For more information, see chapter 11.3.1 Motion Control
Options.
11.4 Accessories
11.4.1 Brake Resistors
In applications where the motor is used as a brake, energy
is generated in the motor and sent back into the
adjustable frequency drive. If the energy cannot be
transported back to the motor, it increases the voltage in
the adjustable frequency drive DC line. In applications with
frequent braking and/or high inertia loads, this increase
may lead to an overvoltage trip in the adjustable
frequency drive and finally a shutdown. Brake resistors are
11 11
used to dissipate the excess energy resulting from the
regenerative braking. The resistor is selected in respect to
its ohmic value, its power dissipation rate and its physical
size. Danfoss offers a wide variety of different resistors that
are specially designed to our adjustable frequency drives.
See chapter 5.5.3 Control with Brake Function for
dimensioning of brake resistors. Code numbers can be
found in chapter 7 How to Order.
11.4.2 Sine-wave Filters
When a motor is controlled by an adjustable frequency
drive, resonance noise is heard from the motor. This noise,
which is the result of the motor design, arises every time
an inverter switch in the adjustable frequency drive is
activated. The frequency of the resonance noise thus
corresponds to the switching frequency of the adjustable
frequency drive.
For the FC 300, Danfoss supplies a sine-wave filter to
dampen the acoustic motor noise.
182
®
Positioning Controller MCO
Design Guide
The filter reduces the ramp-up time of the voltage, the
peak load voltage U
motor, which means that current and voltage become
almost sinusoidal. Consequently, the acoustic motor noise
is reduced to a minimum.
The ripple current in the sine-wave filter coils also causes
some noise. Solve the problem by integrating the filter in a
cabinet or similar.
11.4.3 dU/dt Filters
dU/dt filters are differential-mode low-pass filters which
reduce motor terminal phase-to-phase peak voltages and
reduce the rise time to a level that lowers the stress on the
insulation at the motor windings. This is especially an issue
at short motor cables.
Compared to sine-wave filters (see chapter 11.4.2 Sine-wave
Filters), the dU/dt filters have a cut-off frequency above the
switching frequency.
11.4.4 Common Mode Filters
High frequency common mode cores reduce electro-
magnetic interference and eliminate bearing damage by
electrical discharge. They are special nanocrystalline
magnetic cores which have superior filtering performance
compared to regular ferrite cores. They act like a common-
mode inductor (between phases and ground).
Installed around the three motor phases (U, V, W), the
common mode filters reduce high-frequency common
mode currents. As a result, high frequency electromagnetic
interference from the motor cable is reduced.
11.4.5 Harmonic Filters
The Danfoss AHF 005 and AHF 010 are advanced harmonic
filters not to be compared with traditional harmonic trap
filters. The Danfoss harmonic filters have been specially
designed to match the Danfoss adjustable frequency
drives.
By connecting the Danfoss harmonic filters AHF 005 or
AHF 010 in front of a Danfoss adjustable frequency drive,
the total harmonic current distortion generated back to
line power is reduced to 5% and 10% respectively.
Rev. 2014-04-04 All rights reserved.
and the ripple current ΔI to the
PEAK
MG33BF22