This is a mount for the detachable VFD (Variable Frequency Drive) control panel for a SUSWE model SU800900 VFD. These are a very nice, inexpensive, Chinese inverters used to operate a large three-phase motor at variable speed.

The small control panel detaches from the main inverter and can be located remotely using a CAT5 (orCAT6) network cable. I had an existing 2 inch (50mm) diameter meter hole that wasn't in use that I wished to repurpose for the panel mount the VFD control. The rear backing plate centers the whole mount in the 2 inch hole. Two M3 countersunk screws hold the front housing to the rear backing plate and clamp the assembly to the sheet metal panel.