Danfoss VLT AHF 005 Design Manual page 30

Requirements for Installati...
To frequency
converter
digital input
4 4
To frequency
converter
relay output
24 V DC
24 – 240 V AC
depending on
contactor type
Illustration 4.14 Parallel Use of AHF Combined with Capacitor Disconnect
NOTICE
It is not allowed to use 1 common 3-poled contactor
with several paralleled filters.
NOTICE
Keep the cable length between the filter and the
capacitor disconnect contactor as short as possible to
reduce the impedance influence on the cable. A
maximum cable length of 2 m (6.6 ft) is allowed between
filter and contactor.
Voltage boost
The AHF is designed to ensure the lowest possible
insertion loss to provide full DC-link voltage in the
frequency converter. The target of this design is to ensure
full DC-link voltage at nominal load, see B in
Illustration 4.15. Providing the full DC-link voltage at
nominal load results in a minor voltage boost at low-load
conditions and a minor voltage drop at overload
conditions. The voltage boost at low load (A in
Illustration 4.15) is approximately 5%, while the voltage
drop at overload (C in Illustration 4.15) is a few
percentages. Illustration 4.15 shows the insertion loss in the
frequency converter as a function of load.
NOTICE
The voltage boost causes the voltage at the frequency
converter terminals to be up to 5% higher than the
voltage at the input of the filter when the capacitors are
not disconnected. Consider this situation when designing
the installation. Take special care in 690 V applications
where the voltage tolerance of the frequency converter
is reduced to +5%, unless a capacitor disconnect is used.
28
®
VLT
X 1.1 X1.2 X1.3
27
A
AHF 1
12
B
X3. 1 X 3.2 X3.3
02
01
Danfoss A/S © 10/2016 All rights reserved.
Advanced Harmonic Filter AHF 005/AHF 010
X2.1 X2.2 X2.3
X4.1 X4.2 X4.3
DC-link voltage [%]
A
100
0
A Low-load condition or standby. Approximately 5%
voltage boost occurs without the capacitors being
disconnected. If the capacitors are disconnected, the
voltage boost can be reduced.
B Nominal load condition. The AHF is optimized for full
DC-link voltage in the frequency converter at nominal
load conditions.
C Overload condition. A voltage drop of a few
percentages occurs at high overload conditions.
Illustration 4.15 Insertion Loss in the Frequency Converter as a
Function of Load
NOTICE
Only switch the contactor at less than 20% output
power. Allow minimum 25 s for the capacitors to
discharge before reconnecting. See more details in
chapter 6 Programming.
X1.1 X1.2 X1.3 X2. 1 X2.2
A
AHF 2
B
X3.1 X3.2 X3.3 X4.1 X4.2
B
100
X2.3
X4.3
C
150/160
Load [%]
MG80C502