Electronics > Mechanical & Automation Engineering

Servo drives exploding after changing EMI filter

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jurgis1991:
Hi,we have a CNC machine that uses 7 servo drives (3 phase drives, Yaskawa 200V). Recently, someone destroyed (shorted phases together) one of the motor wires, which caused the drive to explode. The drive and wire were replaced,but we noticed that the EMI filter had one phase burned out, so we replaced the EMI filter (a no-nema chines 3-phase filter) with a 3-123-506 mains filter, a 3-phase 64A 760V 900uOhm Schurter filter. After the replacement, when we powered up the CNC, one of the drives exploded. The safety capacitors (from phases to ground) and MOV had exploded. We checked all the phases and neutral ground wires and found one that seemed to be lost. After we powered again and a different drive was expeloded (MOVS that goes between phases),
So now I really don't know what to do. Can the problem be that the new EMI filter does not filter the noise as well as the old one, which causes big voltage spikes that destroy MOVS?

Thanks for the help!

Jeroen3:
Are you confident the power feed is still solid? No missing or high impedance neutral or earth?

jurgis1991:
Yes, I verified every connection and attempted to load a natural wire while measuring the voltage to ground.

Jeroen3:
The thing that bothers me most of your story is that you say the Y-capacitor to earth and a MOV exploded.
Suggesting an overvoltage between two phases and phase and earth.

Could there still be a short present somewhere?

jurgis1991:
Wouldn't the main fuse blow rather than the MOVs if there was still a short?

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