Hitachi WJ200 Series Quick Reference Manual page 106

As described on page 4-14 of the Instruction manual,
flowing into itself when it is not powered. This may cause the closed circuit when two or
more inverters are connected to common I/O wiring as shown below to result in
unexpected turning the on the input. This may lead to dangerous situation. To avoid
this closed circuit, please put the diode (rated:50V/0.1A) in the path as described
below.
IF the protection diodes used when the units are in wired parallel are only single diodes
then their condition would be checked as part of the proof test.
In case of Sink logic
Jumper
wire
Jumper
wire
Switch
OFF
In case of Source logic
Jumper
wire
Jumper
wire
Switch
OFF
The current loop cause turn the input ON
even the switch is off when diode is not
inserted.
Power ON
P24
PLC
L
Input
ON
1
Inserting
Power OFF
P24
PLC
L
1
P24
PLC
L
Input
ON
1
Inserting
P24
PLC
L
1
inverter doesn't block the current
diode
Switch
OFF
diode
Switch
OFF
The current loop is to be prevented by
inserting diode instead of Jumper wire.
100
Power ON
P24
PLC
L
Input
OFF
1
Power OFF
P24
PLC
L
1
P24
PLC
L
Input
OFF
1
P24
PLC
L
1