The single-phase system and the three-phase system differ due to the voltage they pass through.
• Single-phase system = the voltage between phase and neutral is 230V
• Three-phase system = the voltage is 400V between the 2 phases and 230V between the phase and neutral.
The UPS (uninterruptible power supplies) Three-phase | Single-phase are connected to the three-phase electrical network (400V) and provide single-phase 230V output to the connected loads.