Making a reliable installation here will be difficult.

1/ Motor cable screening, there is no motor cable screening within the panel.

2/ Panel backplate, this is a painted, bonding the inverter chassis will not be efficient.

3/ Line chokes, these appear to be between the inverter and the motor, interconnecting cables are not screened.

The PWM (Pulse Width Modulation), provided by the inverter drives is probably 4 kHz, adding to this the 'ringing', a byproduct of this, there will be emission's in the region of MHz, radiating from the motor cables, within this enclosure. There is no cable separation of inverter cables within the enclosure.

Further, high frequencies of this order will be leaking capacitively from the motor's, these currents will be finding the lowest impedance route back to the enclosure, and the inverter drives supplying the power. The fact that the inverters are mounted on a painted backplate, with poor bonding, will impede this return path.

The result will be serial communications heavily influenced and damaged by the high frequency emissions within the enclosure and return currents from the motors.

My recommendation would be to rebuild the enclosure, to a galvanized backplate, with screened cables for all inverter output cables.

Ensure all motor cables are supplied via screened or armoured cables, terminating screening at motor end and, enclosure entry through glands terminating the screen by clamping. Enclosure glands to be bonded to the galvanized backplate.

I realise this will be difficult and, If I can help further with any recommendations please come back.

Tractor

Good, the machine is running for production, but bear in mind there are issues with this installation which may cause further problems.

Many thanks for coming back with progress.

Tractor 

Akash

I understand the production is now working which is good, whilst there are some issues with this enclosure, the main this is to get production going.

I have attached a pic of a new panel, which shows how these interconnections can be achieved for future installations, which may also help other Engineers who have to manage operation with inverter drives.

Tractor