ABB ACS2000 AFE 2MVA, User Manual

Page: 38 / 181

CHAPTER 2 – POWER ELECTRONICS AND CABINET FEATURES 38
2.3.4 DC link
The DC link consists of the charging unit (1) , the
capacitors (2) , and the grounding switch (3) .
Charging unit
Charging
The unit charges the DC link capacitor and the
phase capacitors before the MCB is closed to con-
nect the drive to the main power supply. Thus,
excessive inrush currents are prevented.
The charging unit is fed from the auxiliary power
supply and charges the DC link and the phase
capacitors to 90% of the steady-state voltages.
The charging sequence is started by pressing the
SUPPLY ON push-button on the control compart-
ment door. After the charging sequence has fin-
ished, the charging unit is disconnected from the
medium voltage circuit, the MCB is closed, and the
DC link will reach its nominal level.
Stand-by mode
Once the DC link is charged, it is possible to keep
the drive in this state to facilitate a more rapid
start-up procedure. The losses during stand-by
mode are approx. 1% of the nominal power and are
caused from small losses from the AFE, the INU,
and the auxiliaries.
Discharging
Discharging is initiated by pressing the
SUPPLY
OFF pushbutton on the control compartment door.
The DC link capacitors will then discharge via the
IFU. The energy stored in the DC link is dissipated
in the parasitic resistors of the power part of the
drive. When the DC link voltage has decreased
below a quarter of the DC link voltage, the capaci-
tors in the phase modules start to discharge as
well.
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References
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2-8 DC link
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2-8
1
3
2
2