Can I program a VFD without it being connected to the main power supply?

This depends on the drive model.

• MS300, ME300, MH300 Series - Yes, Connecting a USB will power the board and allow programming.
• C2000 or CP2000 - You will first need a CMC-BPS01 card then you can apply 24v DC to program the drive without the main power being connected.
• Other drives - Check the manual to see if that drive has a built in USB port for programming, if so it can be powered by the USB port. If not check the drive manual to see if it supports the CMC-BPS01 card, and if it does you can program it without the main power supply.