Minor arc flash burn to left hand
September 13, 2019
An electrician was going to replace the fuse holder in a VFD cabinet. The line side terminals were loosened to remove the conductors, the local disconnect was off but the main motor control center disconnect was still on so the conductors were still energized. When the electrician tried to remove the wires an arc flash occurred damaging the individual’s hand and the inside of the cabinet as shown.
The Sawmill would have motors for conveyors and for feed rolls that feed logs through the machines. These motors can be driven by Variable frequency drives (VFD) to control the speed of the logs as they are cut by each machine. Some machines can have a complete motor control center full of variable frequency drives due to the large number of motors on the machine. Lockout is accomplished at two locations, Local, at the VFD cabinet, and at a feeder disconnect that removes all power off the MCC. Local disconnects only remove power from the cabinet they are mounted on.