When looking at the TRH50A (50W) series of power supplies you will find the suffix VI on many of the parts. This represents the efficiency rating of the power supply. Here is a snippet from the application notes detailing the different efficiency classifications.
Image courtesy of PW174KB_DS.pdf (slpower.com) please see the linked document for more information
Applicable Part Numbers
| Digi-Key Part Numbers | Manufacturer Part Numbers |
|---|---|
| 2034-TRH50A240-01E03VI-ND | TRH50A240-01E03 VI |
| 2034-3886-ND | TRH50A120-11E01 VI |
| 2034-TRH50A280-01E03VI-ND | TRH50A280-01E03 VI |
| 2034-TRH50A190-01E03VI-ND | TRH50A190-01E03 VI |
| 2034-TRH50A180-01E03VI-ND | TRH50A180-01E03 VI |
| 2034-TRH50A480-01E03VI-ND | TRH50A480-01E03 VI |
| 2034-3888-ND | TRH50A180-11E01 VI |
| 2034-3890-ND | TRH50A480-11E01 VI |
| 2034-TRH50A360-01E03VI-ND | TRH50A360-01E03 VI |
| 2034-3887-ND | TRH50A150-11E01 VI |
| 2034-3889-ND | TRH50A240-11E01 VI |