Note you can’t use a wire clamp to measure a 3-phase power cable, you need to measure each phase by itself.
48V (telco land, NEBS standard) and other versions that are being tried, (12, 24V). Grounding requirements, power bars. Devices often have different plugs. Most of the time still using A+B circuits Reduced conversions == Reduced losses. Amplified by most larger servers (i.e. HP C7000, SuperDome) using 48V internally. Even more interesting with large UPS banks since those also use 48V.