Chapter 5 Wiring
Solving noise problem
5-15
TP03
AC Power input
AC Power source
Isolation transformer
The closer the isolation transformer located to PLC input, the better. AC power wire should be
twisted wire. The capacity of isolation transformer should be more than 120% consumption
capacity of PLC, or the voltage at primary side of transformer would larger than rated one that will
undermine safety.
Terminal block Twisted Wire
AC Power source
Isolation transformer
TP03
AC Power input
Please add a voltage tap to secondary side of transformer if the capacity of transformer is larger.
The power supply for PLC should be a single one when noise is very serious. And several
transformers are recommended.
pr i mar y
si de
110V
100V
90V
0V
AC Power supply
For TP03 power supply terminals
For Load
MCCB
5.2 Solving thunder stroke problem
When the factory installing PLC is far away from other buildings, the installation of PLC must take
thunder stroke problem into consideration. (Thunder stroke may induce surge voltage up to
4000KV). A surge protector must be installed to reduce the high voltage and protect PLC. It is
recommended to install a surge protector according to the equipment installed and power capacity.
Please refer to following diagram for the installation of and outdoor 1.7KAV surge protector.
TP03
FG
E
MCCB
breaker
AC i nput
AC250V input
Surge protector
Special Class 3
groung
（<10Ω ）
other devices
Class 3 ground
Transformer
(drop voltage
)
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