Goodrive300-01A series VFD for air compressor
Common EMC problems and troubleshooting
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Appendix E Common EMC problems and troubleshooting
E.1 Interference problems of meter switches and sensors
The sensor signal (pressure, temperature, displacement, etc.) is collected and displayed via HMI
device, the sensor value displayed after VFD starts is wrong, the common phenomena are listed
below:
Incorrect display of upper limit or lower limit value, such as 999 or -999;
The displayed value changes randomly (often occurred to pressure transmitter);
The displayed value is stable but huge deviation exists e.g. the displayed temperature value is
dozens of centigrade higher than the normal value (often occurred to thermocouple);
The signal collected by the sensor does not display directly but acts as feedback signal for drive
system operation e.g. the VFD is supposed to decelerate when the air compressor has reached
the upper limit pressure, however, the VFD starts to decelerate before upper limit pressure is
reached;
Various meters connected by VFD analog output (AO) (such as frequency meter, current meter,
etc.), the value displayed by these meters after VFD starts is inaccurate;
The system adopts proximity switch. The indicator of proximity switch flickers after VFD starts,
overturn occurred to output level by mistake.
Solution
Check and confirm the sensor feedback line is routed with motor cable at a distance of at least
20cm;
Check and ensure motor ground line has been connected to PE terminal of the VFD (if motor
ground line has been connected to the grounding bar of VFD cabinet, measure with multimeter to
confirm that the resistance between grounding bar and PE terminal is less t
han 1.5Ω);
If there are too many interfered meters/sensors, it is recommended to install external C2 filter at
the input power side of the VFD.
E.2 485 communication interferences
The 485 communication interference mainly lies in communication delay, out-of-synchronization,
disconnection or occasional normal after VFD starts.
Abnormal communication is not always caused by interference, which can be ruled out by below
means.
Check if circuit break or poor contact occurred to 485 communication bus;
Check if both ends of A, B cable of the 485 communication bus are connected reversely.
Check if the communication protocol (e.g. baud rate, data bit check, etc.) of the VFD is in
consistent with that of the upper PC;
If it is confirmed that the abnormality is caused by interference, rule out the problem cause by below
means.
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