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Installation guide / User manual
AX Plus 5-15kW 3ph Hybrid Inverter
create a shock hazard. Prior to touching any part of the inverter please ensure
surfaces and equipment are under touch safe temperatures and voltage
potentials before proceeding.
2.2 PE Connection and Leakage Current
PV System Residual Current Factors
• In every PV installation, several elements contribute to the current leakage to
protective earth (PE). these elements can be divided into two main types.
• Capacitive discharge current - Discharge current is generated mainly by
the parasitic capacitance of the PV modules to PE. The module type, the
environmental conditions (rain, humidity) and even the distance of the
modules from the roof can effect the discharge current. Other factors that may
contribute to the parasitic capacitance are the inverter's internal capacitance
to PE and external protection elements such as lighting protection.
• During operation, the DC bus is connected to the alternating current grid
via the inverter. Thus, a portion of the alternating voltage amplitude arrives
at the DC bus. The fluctuating voltage constantly changes the charge state
of the parasitic PV capacitor (i.e capacitance to PE). This is associated with
a displacement current, which is proportional to the capacitance and the
applied voltage amplitude.
• Residual current - if there is a fault, such as defective insulation, where an
energized cable comes into contact with a grounded person, an additional
current flows, known as a residual current.
Residual Current Device (RCMU)
• All inverters incorporate a certified internal RCMU (Residual current monitoring
unit) to protect against possible electrocution in case of a malfunction of the PV
array, cables or inverter (DC). The RCMU in the inverter can detect leakage on the
DC side. There are 2 trip thresholds for the RCMU as required by the DIN VDE 0126-
1-1 standard. A low threshold is used to protect against rapid changes in leakage
typical of direct contact by people. A higher threshold is used for slowly rising
leakage currents, to limit the current in grounding conductors for the safety.
Installation and Selection of an External RCD device
• An external RCD is required in some countries. The installer must check
which type of RCD is required by the specific local electric codes. Installation
of an RCD must always be conducted in accordance with local codes and
standards. a-TroniX recommends the use of a type-A RCD. Unless a lower
value is required by the specific local electric codes, suggests an RCD value
between 100mA and 300mA.
atx054en0225
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