I. Basic Concepts and Topological Structure Analysis

Before discussing the technical characteristics of UPS (Uninterruptible Power Supply), it is necessary to clarify the core concept of "topology". In power electronics, topology refers to the structural layout of circuit components, determining energy transmission paths and system performance—critical for understanding UPS classifications.

In China, 220V is single-phase power, and 380V is three-phase power. The "single" and "three" in UPS denote input/output phase configurations.

(1) Single-Input Single-Output (1:1) UPS

A Single-Input Single-Output (1:1) UPS features single-phase AC input (220V) and single-phase AC output (220V). Its topology uses a single-phase rectifier to convert 220V to DC, then a single-phase inverter to restore stable 220V AC. Key components include a rectifier module, battery, inverter, and static switch.

Connecting to a single-phase grid (live+neutral+ground), it suits devices like PCs and printers. With simple topology, it dominates small UPS systems (0.5–10kVA).

(2) Three-Input Single-Output (3:1) UPS

A Three-Input Single-Output (3:1) UPS has three-phase AC input (380V) and single-phase AC output (220V). Its three-phase rectification system accepts 380V three-phase four-wire input (A/B/C+neutral+ground), converting it to DC before inverting to 220V single-phase AC. This design balances grid loads while supporting high-power single-phase devices.

Ideal for medium-power scenarios (10–50kVA) like data centers and hospital departments, its three-phase input mitigates grid imbalance issues.

(3) Three-Input Three-Output (3:3) UPS

A Three-Input Three-Output (3:3) UPS offers three-phase AC input and output (380V). With complex topology, it receives 380V three-phase power, rectifies to DC, and inverts back to 380V three-phase AC. Equipped with redundant modules and intelligent monitoring, it serves large three-phase loads (e.g., industrial motors, CT scanners).

Boasting exceptional grid adaptability, its capacity ranges from 50kVA to multiple MVA, making it critical for data centers, ICUs, and other high-reliability environments.

II. Comparative Analysis of Technical Characteristics

(1) Input/Output Phase Configuration

· 1:1 UPS: 220V single-phase in/out, for household/office loads.

· 3:1 UPS: 380V three-phase input/220V single-phase output, for industrial grids and clustered devices.

· 3:3 UPS: 380V three-phase full configuration, directly powering large three-phase equipment.

(2) Capacity Range

· 1:1 UPS: ≤10kVA (single-phase input limit).

· 3:1 UPS: 10–50kVA (three-phase input expansion).

· 3:3 UPS: Hundreds of kVA to MVA (suitable for airport hubs, etc.).

(3) Grid Compatibility

· 1:1 UPS: May unbalance industrial grids.

· 3:1 UPS: Balances loads via three-phase input.

· 3:3 UPS: Maintains optimal three-phase balance with superior power factor.

(4) System Reliability

3:3 UPS integrates redundant modules (e.g., parallel rectifiers) and hot-swappable features, outperforming 1:1 and 3:1 models in reliability. 1:1 UPS suits non-critical scenarios due to simple design.

III. Typical Application Scenarios

(1) 1:1 UPS Applications

Suitable for small offices, homes (e.g., PC+router), and small medical devices (bedside monitors). Example: A 1kVA 1:1 UPS protects home NAS storage during outages.

(2) 3:1 UPS Applications

Ideal for medium commercial setups, like 200-server data centers (220V per server). A 30kVA 3:1 UPS uses 380V input to power the cluster, preventing grid imbalance.

(3) 3:3 UPS Applications

Critical for high-reliability environments: large data centers (e.g., Tencent Cloud), hospital ICUs (ventilators). Example: A 200kVA 3:3 UPS with N+1 redundancy ensures continuous operation during cardiac surgeries.

IV. Selection Guidelines

(1) Load Characteristics

· Single-Phase Loads (220V): 1:1, 3:1, or 3:3 UPS are viable. Note: Cost order—1:1 < 3:1 < 3:3. Choose 1:1 for cost-sensitive small setups.

· Three-Phase Loads (380V): Require 3:3 UPS (e.g., industrial motors, production lines).

(2) Grid Conditions

Opt for 3:1/3:3 UPS if 380V three-phase grid is available and load >10kVA. Use 1:1 UPS for 220V single-phase grids.

(3) Redundancy Needs

Mission-critical scenes (ORs, financial systems) demand 3:3 UPS with modular redundancy. General offices can use 1:1 UPS with backup batteries.

(4) Scalability

3:3 UPS allows capacity expansion via parallel modules, while 1:1 UPS typically requires full replacement for upgrades.

V. Conclusion

UPS classifications (1:1, 3:1, 3:3) reflect input/output phase configurations:

· 1:1: 220V single-phase in/out

· 3:1: 380V three-phase in/220V single-phase out

· 3:3: 380V three-phase full configuration

Select based on load type, power, reliability, and budget—1:1 for small single-phase loads, 3:1 for medium single-phase loads, and 3:3 for large three-phase critical systems. Modular 3:3 UPS is increasingly cost-effective, driving broader adoption.