Installation
Grundfos CUE
34
RFI filters
To meet the EMC requirements, the CUE comes with
the following types of built-in radio frequency interfer-
ence filter (RFI).
RFI filter types are according to EN 61800-3.
C1 is a high-performance filter. C2 and C3 are typically
R
FI filter types for standard frequency converters.
Description of RFI filter types
C1: For use in domestic areas.
C2: For use in domestic and industrial areas, con-
nected permanently to the mains supply. In domestic
area
s, special care should be taken regarding EMC-
correct installation.
C3: F
or use in industrial areas with own low-voltage
transformer.
Equipment of category C2
• In a domestic environment this product may cause
r
adio interference in which case supplementary miti-
gation measures may be required.
Equipment of category C3
• This type of power drive system (PDS) is not in-
tended to be used on a low-voltage public network
w
hich supplies domestic premises.
• Radio frequency interference is expected if used on
such a
network.
Output filters
Output filters are used for reducing the voltage stress
on the motor windings and the stress on the motor insu-
lation system as well as for decreasing acoustic noise
fr
om the frequency converter-driven motor.
Grundfos offers two types of output filter as accessories
for
the CUE:
•dU/dt filters
• sine-wave filters
The filters are IP20/NEMA1 enclosure.
dU/dt filters
Motor insulation stress is often caused by the combina-
tion of rapid voltage and current increase. The rapid
ene
rgy changes can also be reflected back to the DC
line in the inverter and cause shut down. The dU/dt filter
is designed to reduce the voltage rise time/the rapid
energy change in the motor, and by that intervention, it
prevents premature aging and flashover in the motor
insulation.
The dU/dt filters have a positive influence on the radia-
tion of magnetic noise in the cable that connects the
dr
ive to the motor. The voltage wave form is still pulse-
shaped but the du/dt ratio is reduced in comparison
with the installation without filter.
Sine-wave filters
Sine-wave filters are designed to allow only low fre-
quencies to pass. High frequencies are consequently
shunt
ed away, which results in a sinusoidal phase-to-
phase voltage waveform and sinusoidal current wave-
forms.
With the sinusoidal waveforms, the use of special
adju
stable frequency drive motors with reinforced
insulation is no longer needed. The acoustic noise from
th
e motor is also damped as a consequence of the
wave condition.
Besides the features of the dU/dt filter, the sine-wave
fi
lter also reduces insulation stress and bearing
currents in the motor, thus leading to prolonged motor
lif
etime and longer periods between service. Sine-wave
filters enable use of longer motor cables in applications
where the motor is installed far from the drive. The
length is unfortunately limited because the filter does
not reduce leakage currents in the cables.
Use of output filters
The table below explains in which cases an output filter
is required. From the table it can be seen if a filter is
needed, and which type to use.
The selection depends of:
• pump type
• motor cable length
• the required reduction of the acoustic noise from the
mo
tor.
Voltage Typical shaft power P2 RFI filter type
1 x 200-240 V 1.5-10 Hp (1.1-7.5 kW) C1
3 x 200-240 V 1-60 Hp (0.75-45 kW) C1
3 x 380-500 V
0.75-125 Hp (0.55-90 kW) C1
150-350 Hp (110-250 kW) C2
3 x 525-600 V 1-10 Hp (0.75-7.5 kW) C3
3 x 525-690 V 15-350 Hp (11-250 kW) C3
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