When the drive arrived we performed an evaluation and formulated a failure analysis. Their failure was due to an improperly placed IGBT within the U phase:
An IGBT’s Heatsink Mounting plate (It’s Backside) is convexly parabolic in shape. This means that to make flat contact when mounted it will require even pressure from the outer edges of the device. Torqueing down all six mounting screws is essential to a flat mount and proper thermal linkage of the device to the Drive chassis heatsink. Heat transfer compound must also be applied to the IGBT to further improve thermal linkage.
The major arc flash event was due to the IGBT over-heating, due to improper thermal linkage, and venting. The IGBT momentarily shorts when over-heated which creates a direct path for the Positive and Negative Bus Voltage causing all the energy stored in the Bus Capacitor banks to discharge instantaneously in an explosive Arc-Flash event. This event caused several other component failures within the drive due to the massive electrical surge, the heat generated by the blast and/or the blast concussion.
The unit was from a Tissue manufacturer and was covered in dust and Lint. The drive had to be totally disassembled and cleaned before any replacement components could be installed. We pressure washed the Heatsink and Chassis, washed all circuit boards, disassembled and cleaned sub-assemblies, polished off any corrosion on the Copper Buswork and remade all damaged Voltage Isolation Insulators.
Once all this work was performed the drive was fully reassembled and tested in a controlled environment at our testing lab. This Drive is now back at the customer facility happily spinning out copious amounts of tissues so our homes can be effectively TP’d this Halloween!