Appendix D. Common Emc Problems And Countermeasures; Interference Problems Of Meter Switch And Sensors; 485 Communication Interference - INVT Goodrive300-21 Series Operation Manual

Goodrive300-21 series dual inverter integrated machine for air compressor

Appendix D. Common EMC problems and countermeasures

D.1. Interference problems of meter switch and sensors
Interference phenomena:
The sensor signal (pressure, temperature, displacement, etc) is collected and displayed via HMI
device, the sensor value displayed after inverter starts is wrong, the common errors are listed as
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 eg 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 act as feedback signal for drive
system operation eg the inverter starts to decelerate once air compressor has reached the
upper limit pressure, however, actually the inverter starts to decelerate before upper limit
pressure is reached;

Various meters connected by inverter analog output (AO) (such as frequency meter, current
meter, etc), the value displayed by these meters after inverter starts is inaccurate;

The system adopts proximity switch. The indicator of proximity switch flickers after inverter
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 inverter (if
motor ground line has been connected to the grounding bar of inverter cabinet, measure with
multimeter to confirm that the resistance between grounding bar and PE terminal is less than
1.5Ω);

If there are too many interfered meters/sensor, it is recommended to install external C2 filter at
the input power side of the inverter.
D.2. 485 communication interference
The 485 communication interference mainly lies in communication delay, out of sync, disconnection
or occasional normal after inverter 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;
- -
95
Appendix D