Welding Machine connections caused earthing cable damage

[Mohsen1]

We have a welding Machine Rated input Voltage 400 Volt (single Phase), 32.2 KVA, 81 A , but we have not 400 Volt single phase, then Electrical Technician connected it as two phase 415 volt, they used this machine for long time at work shop to weld workpieces on Metal table without ground " isolated" with power supply 415 V , two phases in safe condition, however they used this machine at site to weld pipes inside cracker Furnace, they put the current return clamp at earth rod at ground floor and the welding current cable at the pipe "workpiece" inside the furnace at second floor (the furnace already earthed), then once started welding after minutes the ground cable of the machine and the source ground cable burnt.
Please can you explain why earth cable burnt

 

[itsmoked]

Yes, it probably wasn't rated at that welder's 580 amps and over heated.

 

[Barrie66]

You may not have 400V single phase but you sure do have 415V single phase which is quite OK for connection for the welding machine.
Obviously the welding return cable was not properly connected to a low resistance return path so it selectively chose the machine earth wire. A very common occurance in welding shops where the welding person suffers from sleep deprivation or ADD.

 

[treborrenrut]

You must remember that there are two ciruits in use when welding. The primary side of the transformer is fed from the mains and this requires earthing as with all electrical equipment. The secondary side ( the welding ciruit) has a welding torch connection and a work return connection NOT an earth. If the work return is not correctly attached to the job being welded but for example laid on the ground near the job the welding current will try to find a return path and this could be through the earth bonding of the building or earth connections of adjcent equipment.