Parameter Settings - ABB ACS800 Series Hardware Manual

84
Note concerning parallel-connected inverter modules
There is some current deviation between parallel-connected inverter modules due to
slight differences in the components.
Motor cabling of parallel-connected inverter modules produces cable stray
capacitances in a larger scale than in single inverters. When the IGBTs are switched,
high-frequency common mode current flows through these stray capacitances to
earth. The current sum measurement detects the leakage currents as well as "real"
earth faults. Therefore, the trip level should not be set too low.
If there is a fault affecting a phase current in one inverter module e.g. U2 current is
missing, the U2 currents of the other inverter modules are increased accordingly.
The current sum measurement detects the increase in one inverter module.
Because of these reasons, the current sum measurement can indicate an actual
earth fault or a current imbalance situation between the inverter modules.

Parameter settings

The following Standard Application Program parameter setting defines how the drive
reacts when an earth fault is detected:
Parameter 30.17 EARTH FAULT
WARNING
FAULT
For other application programs, refer to their firmware manuals.
Earth fault monitoring in IT (ungrounded) systems (+Q954)
u v
2 2
Current
transducers
The drive generates a warning.
Default
The drive trips on EARTH FAULT (non-parallel-connected inverter modules)
or CUR UNBAL xx (paralled-connected inverter modules).
w
2
i
Σ I
2
R
T
AINT
board
u