Hitachi S1 Series Basic Manual page 174

S1 series standard inverter
the capacitor needs to be added on the terminal of the temperature meter.; if an electronic ruler is
to transmit signals of 0 to 30 V to a PLC signal terminal, the capacitor needs to be added on the
terminal of the PLC.
2. If a large number of meters or sensors are disturbed. It is recommended that you configure an
external C2 filter on the input power end of the inverter.
7.7.2 Interference on communication
Interference phenomenon
The interference described in this section on 485 communication mainly includes communication
delay, out of sync, occasional power-off, or complete power-off that occurs after an inverter is started.
If the communication cannot be implemented properly, regardless of whether the inverter is running,
the exception is not necessarily caused by interference. You can find out the causes as follows:
1. Check whether the 485 communication bus is disconnected or in poor contact.
2. Check whether the two ends of line A or B are connected reversely.
3. Check whether the communication protocol (such as the baud rate, data bits, and check bit) of
the inverter is consistent with that of the upper computer.
If you are sure that communication exceptions are caused by interference, you can resolve the
problem through the following measures:
1. Simple inspection.
2. Arrange the communication cables and motor cables in different cable trays.
3. In multi-inverter application scenarios, adopt the chrysanthemum connection mode to connect
the communication cables between inverters, which can improve the anti-interference capability.
4. In multi-inverter application scenarios, check and ensure that the driving capacity of the master is
sufficient.
5. In the connection of multiple inverters, you need to configure one 120 Ω terminal resistor on each
end.
Solution
1. Check and ensure that the ground wire of the motor is connected to the PE terminal of the
inverter (if the ground wire of the motor has been connected to the ground block, you need to use
a multimeter to measure and ensure that the resistance between the ground block and PE
terminal is lower than 1.5 Ω).
2. Do not connect the inverter and motor to the same ground terminal as the upper computer. It is
recommended that you connect the inverter and motor to the power ground, and connect the
upper computer separately to a ground stud.
3. Try to short the signal reference ground terminal (GND) of the inverter with that of the upper
computer controller to ensure that ground potential of the communication chip on the control
board of the inverter is consistent with that of the communication chip of the upper computer.
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