5.3.2 Intermediate Section
Following the rectier section, voltage passes to the
intermediate section (see Illustration 5.7 and Illustration 5.8).
An LC lter circuit consisting of the DC bus inductor and
the DC bus capacitor bank smooths the rectied voltage.
The DC bus inductor provides series impedance to
changing current. It aids the
ltering process while
reducing harmonic distortion to the input AC current
waveform normally present in rectier circuits.
The DC capacitor bank assembly consists of up to 21
capacitors arranged in series/parallel conguration. The
assembly also contains the bleeder/balance circuitry. This
circuitry maintains equal voltage drops across each
capacitor, and provides a current path for discharging the
capacitors when the drive is powered down.
The intermediate section also includes the high frequency
(HF) lter card. This card contains a high frequency lter
circuit to reduce naturally occurring currents in the HF
range to prevent interference with sensitive equipment
nearby. The circuit, as with other RFI lter circuitry, can be
sensitive to unbalanced phase-to-ground voltages in the 3-
phase AC input line. This sensitivity occasionally results in
nuisance overvoltage alarms. For this reason, the high
frequency lter card contains a set of relay contacts in the
ground connection of the lter capacitors. The relay is tied
to the RFI/HF switch, which can be switched on or oîš‚ in
parameter 14-50 RFI Filter. This setting disconnects the
ground references to all lters in case unbalanced phase-
to-ground voltages create nuisance overvoltage conditions.
Internal Drive Operation Service Guide
MG94A502 Danfoss A/S © 02/2019 All rights reserved. 49
5 5
To Next Page
Loading...
Need help?
General