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What is a 3-phase UPS?

Introduction:
An uninterruptible power supply (UPS) is used to protect critical loads from electrical power disturbances or outages. A 3-phase UPS is used to protect larger loads, typically 10 kW to several MW, which use 3-phase power distribution. A single-phase UPS is used to protect smaller loads, typically less than 10 kW.

3-phase UPSs are used for a wide range of applications:

Data centers, colocation facilities, and computer rooms
Light industry and commercial buildings
Telecommunications and networking
Infrastructure and transportation

A 3-phase UPS is connected between the main power supply and the critical load. “It is typically paired with a battery back-up solution that provides 5-30 minutes of runtime in case of a complete power outage. For additional back-up time, a generator can be installed. The main function of the UPS is to provide an uninterrupted transition from utility grid to batteries, or to the secondary power source, such as a generator.

3-phase UPS technologies:
The most common mode of operation in 3-phase UPSs is called Online Double Conversion. It delivers the highest level of power quality and is historically used to protect critical loads.

In Online Double Conversion mode, the incoming power is converted through an input PFC rectifier stage to DC (direct current) and then converted back to AC (alternating current) by an output inverter. This allows the inverter to generate perfect output power to the load, independent of any voltage and frequency fluctuations on the main power supply.

Batteries are connected to the DC bus and ensure zero transfer time to battery operation when AC input fails. In that case, power supply is delivered by the batteries through the inverter. When AC input power is restored, the PFC rectifier resumes carrying the load and begins charging the batteries.

An increasingly common mode of operation in Schneider Electric 3-phase UPSs is called eConversion mode. It optimizes UPS efficiency while delivering advanced power quality and zero transfer time to double conversion mode or battery operation when AC input power quality fluctuates outside normal operating ranges.

Discover more on our 3-phase UPS product page and eConversion solution page .