A couple of things with the ABB drives:
They do not support RPM, this slows down the response from the drive. There are specific ABB object types (AI,AO,BO,BI,BV,AV, etc.) that can be added to the ORCA directories that will only bring in the basic parameters when a point is queried, so that it does not bog down the comm buss trying to get every parameter from the object. Delta also has a application called BACnet Device Hack were you can set exactly what BACnet services the third party device supports so that you don't try to use a service not supported by the device.
Attached is the lessons learned document fro ABB. The ABB specific ORCAview objects are on the ABB site somewhere. Most reliable baud rate I have found on drives is 38.4kbs. Addresses of the drives should be sequential. Max Master on the last one should be set to last address + 1. Should be on Delta Net2.
Hope this helps.
kontrol out