Vacon NX, Руководство пользователя

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10
vacon • 172 Active front end (NXA)
Local contacts: http://drives.danfoss.com/danfoss-drives/local-contacts/
NOTE! Enough space must be reserved around the resistors to ensure sufficient cooling. Don’t place
any heat sensitive components near the resistors.
Figure 95. Wiring diagram for control unit
10.9 Parelling
The power of the input group can be increased by connecting several Active Front End units in
parallel. Paralleling refers to Active Front End units connected in the same input transformer. Active
Front End units of different power ratings can also be connected in parallel. No communication
between the units is required; they work independently. Manufacturer’s standard LCL filters must
be used for paralleling. If LCL filters other than these are used in Active Front End units connected
in parallel, too large circulation currents may be generated between the Active Front End units. All
Active Front units must be set for 5% drooping and PWM Synch must be set for Enable. See the
Application manual for specific parameter settings.
Each Active Front End unit connected in parallel must have its own short-circuit protection on AC
and DC sides. The fuses are selected in accordance with Section x-x. When paralleling, attention
must be paid to the sufficient short-circuit capacity of the system.
The derating of Active Front End units connected in parallel is 5% of the DC power; this should be
taken into account when selecting the input unit.
If a device is to be isolated from the AC and DC voltages, and other Active Front End units connected
in parallel are also to be used, separate isolators are required in the AC input and DC output. The
AC input can be isolated using a compact circuit-breaker, an ordinary circuit-breaker or a fuse
switch. Contactors are not suitable for isolating the AC input because they cannot be locked in the
safe position. The DC output can be isolated using a fuse switch. The pre-charging circuit must also
be isolated from the AC input. A load isolation switch or safety isolation switch can be used for this.
The device can also be connected to mains even when the other devices connected in parallel are
already connected and running. In such a case, the isolated deice must first be pre-charged. When
that is done, the AC input can be switched on. After this, the device can be connected to the
intermediate DC circuit.
3078.emf
11402 uk