11.3.3 VLT
®
Positioning Controller MCO
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
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
frequency converter. If the energy cannot be transported
back to the motor, it increases the voltage in the
frequency converter DC-line. In applications with frequent
braking and/or high inertia loads, this increase may lead to
an overvoltage trip in the frequency converter and finally a
shut down. Brake resistors are 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 frequency converters. See
for dimensioning of brake resistors. Code
numbers can be found in
11.4.2 Sine-wave Filters
When a motor is controlled by a frequency converter,
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 frequency converter is activated. The
frequency of the resonance noise thus corresponds to the
switching frequency of the frequency converter.
For the FC 300, Danfoss supplies a Sine-wave filter to
dampen the acoustic motor noise.
The filter reduces the ramp-up time of the voltage, the
peak load voltage U
PEAK
and the ripple current
Δ
I to the
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 sinewave filters (see
), 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 frequency converters.
By connecting the Danfoss harmonic filters AHF 005 or
AHF 010 in front of a Danfoss frequency converter the
total harmonic current distortion generated back to the
mains is reduced to 5% and 10% respectively.
11.4.6 IP21/Type 1 Enclosure Kit
IP20/IP4X top/TYPE 1 is an optional enclosure element
available for IP20 compact units.
If the enclosure kit is used, an IP20 unit is upgraded to
comply with enclosure IP21/4X top/TYPE 1.
The IP4X top can be applied to all standard IP20 FC 30X
variants.
Options and Accessories
VLT
®
AutomationDrive FC 301/FC 302 Design Guide, 0.25-75 kW
170
MG33BF02 - Rev. 2013-12-20
11
11