A Hubbell HBL7485 Twist-Lockis a NEMA ML-3P 125/250 Vac ungrounded 15 Amp plug. Its use in 28Vdc systems is non standard. It may be electrically possible to use this for such an application, but having a load equiped with such a connector that could mate with an incorrect supply is dangrous and possibly a code violation (Depending on the code applicable in your area, of course).
The center terminal (in its 125/250 Vac application) is the neutral connection. The two outside blades being 125 V each to the neutral (180 degrees out of phase), for 250 V between them.