current on ground from pump panel to switchgear

[eaglepumpservices]

I have a 1600 amp pump panel which feeds several 100 hp motors driving irrigation pumps.

We are getting current on the ground to the switchgear when we run the motors on a VFD or Cross line.

Is this normal?

 

[dpc]

Voltage?
Service grounded or ungrounded?
Three wire or four wire system?
Magnitude of current measured?
Where was current measured?

In general, there should be very little current in an equipment grounding conductor (green wire).

Does this occur when any motor is running, or just one motor in particular.