Operation Manual – AXA 2400 Compact Power– 30 - 90 kVA
General Description
Document no. 578.650BB
Page 14 of 91
Neutral Voltage Supervision (NVS):
As a standard, the unit is delivered with a jumper wire between the 400 Hz neutral and earth/ground. If
the jumper wire are removed for any reason (eg. Local regulation), the unit monitors the voltage
between the 400Hz neutral and earth/ground.
If this voltage exceeds 42 V (factory setting), the unit shuts down and reports “
NVS FAILURE
”.
To change the setting please refer to Section 6.3 &7.15
Neutral Voltage Displacement Supervision (NVD):
The combination of a grounded converter and an un-grounded aircraft might lead to an energized
aircraft chassis. The reason is the neutral voltage displacement caused by an unbalanced load. In case
the aircraft frame is or will be grounded during operation, a broken neutral might result in arcing as well
as burned ground wires.
The neutral voltage displacement of the aircraft chassis is measured as an AC voltage imposed on the
EF interlock signal.
To change of setting please refer to Section 6.3 & 7.9
Earth Leakage Supervision (ELS)
In systems where the 400 Hz neutral is grounded and there is a break of the cable’s 400 Hz neutral, the
ELS system monitors the residual current in the internal neutral /earth connection. The supervision will
shut down the unit in case the residual current reaches the pre-set level.
For change of setting please refer to Section 6.3 & 7.17
Note!
An additional protection method offered by ITW GSE as an option is the Neutral Conductor Rupture
(NCR). The supervision is based on the presence of an injected current in the neutral conductor (i.e. as
long as the injected current is present, the neutral is intact). The advantage of this method is that a
broken neutral will be detected immediately.
In general ITW GSE does not recommend the NCR option for the following reasons:
1) The need for an additional control wire which is likely to be the first to break.
2) The difficulties of implementing the method in existing installations if a free control wire is not
present.
3) The standard protections built into the Hobart
PoWerMaster
® 2400 series are considered adequate to
safeguard against hazards related to a broken neutral.
