Frequency Inverter ST600 Series High-Performance Multifunction VFD Troubleshooting
-269-
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 a 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 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
VFD is consistent with that of the controlling 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 controlling computer. It is
recommended that you connect the VFD and motor to the power ground, and connect the
controlling computer separately to a ground stud.
3. Try to short the signal reference ground terminal (GND) of the VFD with that of the controlling
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 controlling 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 controlling computer (PLC, HMI,
and touch screen). During this process, pay attention to the voltage of the power supply and the
voltage endurance capability of the capacitor. Alternatively, you can use a magnet ring (Fe-based
nanocrystalline magnet rings are recommended). Put the power L/N line or +/- line of the controlling
computer through the magnet ring in the same direction and wind 8 coils around the magnet ring.
To Next Page
Loading...
