Wiring
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4.7.3.2 Site wiring
Power supply wiring: the power should be separated supplied from electrical transformer.
Normally it is 5 core wires, three of which are fire wires, one of which is the neutral wire,
and one of which is the ground wire. It is strictly prohibitive to use the same line to be
both the neutral wire and the ground wire
Device categorization: there are different electric devices contained in one control
cabinet, such as inverter, filter, PLC and instrument etc, which have different ability of
emitting and withstanding electromagnetic noise. Therefore, it needs to categorize these
devices into strong noise device and noise sensitive device. The same kinds of device
should be placed in the same area, and the distance between devices of different
category should be more than 20cm.
Wire Arrangement inside the control cabinet: there are signal wire (light current) and
power cable (strong current) in one cabinet. For the inverter, the power cables are
categorized into input cable and output cable. Signal wires can be easily disturbed by
power cables to make the equipment malfunction. Therefore when wiring, signal cables
and power cables should be arranged in different area. It is strictly prohibitive to arrange
them in parallel or interlacement at a close distance (less than 20cm) or tie them
together. If the signal wires have to cross the power cables, they should be arranged in
90 angles. Power input and output cables should not either be arranged in interlacement
or tied together, especially when installed the EMC filter. Otherwise the distributed
capacitances of its input and output power cable can be coupling each other to make the
EMC filter out of function.
4.7.3.3 Ground
Inverter must be ground safely when in operation. Grounding enjoys priority in all EMC
methods because it does not only ensure the safety of equipment and persons, but also
is the simplest, most effective and lowest cost solution for EMC problems.
Grounding has three categories: special pole grounding, common pole grounding and
series-wound grounding. Different control system should use special pole grounding,
and different devices in the same control system should use common pole grounding,
and different devices connected by same power cable should use series-wound
grounding.
4.7.3.2 Leakage Current
Leakage current includes line-to-line leakage current and over-ground leakage current.
Its value depends on distributed capacitances and carrier frequency of inverter. The
over-ground leakage current, which is the current passing through the common ground
