rpoet
Member
Hi All,
I've inherited a scenery elevator with a 480v 40HP induction motor which is VFD controlled. In the machinery pit, there is a 3ph, 60A FUSED disconnect between the motor and the drive. I presume it's there to satisfy the requirement for local disconnect for maintenance. I have no problem with that (though I take issue that there's no AUX contact in the disconnect to inhibit the drive when it's off - I'm already going to fix that).
I am wondering about the appropriateness of the fuses in the disconnect though. Are they A) necessary and B) a good idea? To my knowledge, there should be no need for fuses as the drive will protect the motor (assuming the drive is set up correctly, which it is).
Should I replace the disconnect with a non-fused version or slug the fuse holders with a non-fuse element? To my mind, there should be no way to drop a leg on the motor, as that might lead to blowing the drive's output (opening under load).
Thoughts? Thanks!
-rpoet
I've inherited a scenery elevator with a 480v 40HP induction motor which is VFD controlled. In the machinery pit, there is a 3ph, 60A FUSED disconnect between the motor and the drive. I presume it's there to satisfy the requirement for local disconnect for maintenance. I have no problem with that (though I take issue that there's no AUX contact in the disconnect to inhibit the drive when it's off - I'm already going to fix that).
I am wondering about the appropriateness of the fuses in the disconnect though. Are they A) necessary and B) a good idea? To my knowledge, there should be no need for fuses as the drive will protect the motor (assuming the drive is set up correctly, which it is).
Should I replace the disconnect with a non-fused version or slug the fuse holders with a non-fuse element? To my mind, there should be no way to drop a leg on the motor, as that might lead to blowing the drive's output (opening under load).
Thoughts? Thanks!
-rpoet