Hello,

DC drive is found failed. Control, power and field cards are all damaged. One thyristor at the input side is damaged. Field fuses are blown. Input fuses are also blown. Drive placed near to this drive is also damaged. Checked the motor. Motor is okay. What can be the reason?

Hello,

I presume it is 6RA80

When did it happened? Start of drive or during stopping of drive?

Was any fault/alarm displayed/triggered before drive failure?

Have you carried out any parameter changes before the problem? Any optimisation etc. etc. 

Ramp up ramp down time changed?

Modified any wiring, i.e. short circuit between power & control wiring?

Is any electrical supply voltage fluctuation/overshooting problem?

Have you used SITOR fuse link as per drive capacity at drive AC insput side?

Was any change in load intertia? 

Is drive & motor capacity correct or drive is of undersize capacity?

Masru

Voltage fluctuation is a major problem here. But after the drive failure, it is found that the motor armature cable is damaged near the motor terminals. An ABB VFD installed in another panel also failed . No changes were made in the drive parameters and programming. 

some thunderstorm when the problem happened ?

Masru

Voltage fluctuation is a major problem here. But after the drive failure, it is found that the motor armature cable is damaged near the motor terminals. An ABB VFD installed in another panel also failed . No changes were made in the drive parameters and programming. 

Have you provided SITOR fuse of adequate capacity at AC input side?

Is choke of correct capacity installed at drive AC input side? 

I don't think power fluctuation would damage the drive. It could be becuase of heavy short circuit at drive output side which is why control circuit/cards are also damaged. Please check the drive power protective earth conductor size & connection.

HTH. 

Was their any sudden change in load intertia? or is the line supply hardware wiring disconnected or power failed during regeneration? Was their SITOR fuse link at DC out put?

If it was normal load behaviour then regeneration won't be a probelm. 

Yes it could be one of the reason of failure of other drive.

For 80 HP drive 4 sq mm earth cable is too small to handle fault current. It should be atleast of 50 or 70 sq mm size. Also please note, earth conductor should  not be looped one. Please provide separate earthing for individual drive.

HTH. 

Okay!

Should we add fuse link at the output of the drive?

Where can I get the earth wire size chart for drives?