IPE300 series engineering VFD Troubleshooting
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7.7.2 Interference on RS485 communication
The interference described in this section on RS485 communication mainly includes communication
delay, out of synchronization, occasional power-off, or complete power-off that occurs after the VFD is
started.
If the communication cannot be implemented properly, regardless of whether the VFD is running, the
exception is not necessarily caused by interference. You can find out the causes as follows:
1. Check whether the RS485 communication bus is disconnected or in poor.
2. Check whether the two ends of line A or B are connected.
3. Check whether the communication protocol of the VFD is consistent with that of the upper
computer. Check whether the communication protocol (such as the baud rate, data bits, and
check bit) of the VFD 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-VFD application scenarios, adopt the chrysanthemum connection mode to connect the
communication cables between VFDs, which can improve the anti-interference capability.
4. In multi-VFD application scenarios, check and ensure that the driving capacity of the master is
sufficient.
5. In the connection of multiple VFDs, 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 VFD
(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 VFD and motor to the same ground terminal as the upper computer (PLC,
HMI, and touch screen). It is recommended that you connect the VFD 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 VFD with that of the upper
computer controller to ensure that ground potential of the communication chip on the control
board of the VFD is consistent with that of the communication chip of the upper computer.
4. Try to short GND of the VFD to its ground terminal (PE).
5. Try to add a safety capacitor of 0.1 μF on the power terminal of the upper computer (PLC, HMI,
and touch screen). During this process, pay attention to the voltage of the power supply and the
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