
50 User Guide DLX Series L00410623-1
5.3.3. Frequency Monitoring
The inverter repeats the test sequence, but now with the frequency trip limits. First, the
upper frequency trip level is ramped down from the maximum allowed frequency level,
and decreased until it equals the current grid frequency. The time it takes from
equalization to disconnection is measured.
AC max
Maximum allowed frequency; trip level
AC off
Disconnection frequency level; equalization
t
max
Maximum allowed disconnection time
t
off
ime from equalization to disconnection
PASS
he third sequence is successfully carried out
FAIL
he third sequence has failed – try again later
Second, the under frequency monitoring is checked. The trip level is ramped up from the
minimum allowed frequency level, and increased until it equals the current grid frequency.
The time it takes from equalization to disconnection is measured.
AC min
Minimum allowed frequency; trip level
AC off
Disconnection frequency level; equalization
t
max
Maximum allowed disconnection time
t
off
ime from equalization to disconnection
PASS
he fourth sequence is successfully carried out
FAIL
he fourth sequence has failed – try again later
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