I was thinking the same as Joe - High input Z Meter reading leakage from the VFD.
Try connecting a "Real Wiggy" to the open Disconnect Switch, and see if it Buzzes (the Wiggy).
No Buzz = leakage from VFD.
Yes Buzz: see what the Voltage reading is shown on the Wiggy, as described below:
- Nice and solid pull-in, with indicator steady at apx. 600V would mean a large level of current may flow;
- Sluggish, or extremely light pull-in with very low Voltage shown would mean the leakage is quite large;
- Rapidly decaying pull-in, with nothing shown steady would mean a "Normal" level of leakage.
Just my 2¢
BTW "Real Wiggy" = an actual Solenoid-Type Wiggy.
Equivalent would be a low input Z Voltmeter with a 1000VAC scale.
Be sure to use CAT III rated equipment for these tests.