The phrase three-phase UPS is incomplete unless the input and output are both stated. A 3/1 system accepts three-phase input and supplies single-phase output. A 3/3 system has three-phase input and three-phase output.
Read the configuration before the capacity
RAPSTECH’s published BR931 15–20kVA brochure specifies 3/1. Its product family label also uses the words single phase, referring to the output arrangement. Writing three-phase input / single-phase output avoids misunderstanding. The VI933 rack/tower family is listed as 3/3. Confirm the exact offered model and documentation.
Ask what the load needs
Provide required output, distribution arrangement, connected equipment, load demand and growth plan. Do not replace a 3/3 requirement with a 3/1 unit simply because the kVA number is the same. Qualified project personnel should assess equipment compatibility, distribution, protection and earthing.
Keep batteries and bypass in the discussion
Specify the backup objective and ask for battery/runtime assumptions. Review mains-to-battery and inverter-to-bypass transfer separately, using the current model document. Operating-mode headlines should not substitute for an application review.
Phase brief to send with an enquiry
Record available input, required output, exact application, measured or documented load, distribution constraints, runtime, battery space and site location. Include existing drawings if available. Ask the supplier to identify every assumption and any departure from the requested arrangement.
Does three-phase input guarantee three-phase output?
No. Check both sides of the configuration. 3/1 and 3/3 are different arrangements.
Does a 20kVA rating identify the phase?
No. Capacity does not specify the input/output arrangement.
Compare three-phase UPS configurations, review the BR931 product page and request a phase-specific quotation.