Hi everyone,

I am having serious trouble with motor failures on a newly built site.

In short, the system consists of 10 Siemens 1LE1 30kW motors, each motor connected to its own VFD, not dependent of each other.

VFD used are ABB ACS880. 

After around 30h of working time 6 of 10 VFD show fault 2340 - short circuit in motor or cable. We tested the cable and confirmed OK, the drives output was also confirmed as ok.
After measuring the motor winding resistance we found different resistance across winding for exmp. U1-U2 -> 4ohm, V1-V2 -> 4 ohm, W1-W2 -> 2 ohm . Results were similar for all motors.
The difference in winding resistance lead to current imbalance and probably to short circuit fault detected by the VFD. After the event all six motors were taken for rewinding and reinstalled in the system, they work fine now.

I am desperate for any idea you might have why this happened and how to prevent it from happening again.
I am having trouble to believe that 6 from 10 new Siemens motor had some factory mistake.

Also, in such case why didn't the VFD give the fault after the first start? Only after approx 30 working hours the VFD started giving this fault.

Tank you for any advice/help

BR 

Hi, 

thank for your answer. 

The drive code is 1LE10012AA435AB4-Z, as much as I understand from the catalog, this is not a motor ment for VFD operation. 

Could you please confirm my findings? 

Thank you