“I can pick up the "hash" around the conduit and in the general area of the meter with an AM radio. It is the same hash that can be detected next to the drive enclosures themselves.”
How is the grounding at the Drives?
____ASSUMING THE ARRESTOR SYSTEM AND THE PROTECTIVE EARTH ARE SUPPOSED TO BONDED TOGETHER____
How is the bonding between the arrestor system and the service entrance? What is the voltage between the neutral feeding the VFD’s and the arrestor system?
Using the radio, check for hash along the motor conduits especially in the area of the ground system bonding. If the hash does not change where the bonding occurs, I would suspect that the bonding connection is not secure.
Try a temporary jumper from the conduit bare metal to the copper braid. See if the hash changes. When you are dealing with RF noise, the long run of pipe looks like a high impedance path.
“Power was checked with a true RMS meter and no voltage spikes or harmonics are evident.”
Where? The Service entrance, the TDS equipment, the input of the VFD’s, or the output of the VFD’s?
LarryC
