When purchasing UPS for your business or organization, many factors should be taken into consideration, among which the choice of power supply between single phase UPS and three phase UPS is the foremost one. Though both of the UPS offer consistent backup power for dealing with unexpected situations, they have different roles. Here is a brief introduction of single phase vs three phase for those who are unfamiliar with their difference.
What Is the Phase in Electrical Terms？
If you are new to the world of electrical power, you may know little about the term phase. Phase, at its most basic, is the distribution of electrical power, which shows the alternating current (AC) power supply varies with respect to the time period. There are one phase, two phase and three phase power supply types.
Single phase is commonly called “residential voltage” because it is widely available in homes. For example, the microwave oven, the coffee machine, your PC in your household can be single phase devices. In different regions there is a similarity for single phase connections: It requires two wires (one voltage wire and one neutral wire) for completing the circuit. The figure below shows the current flow in single phase AC power.
Figure 1: Single phase AC power
Two phase is basically the same thing as single phase, which consists of AC with two wires. It is also called the split phase. The power is supplied by either one of the two 120V power circuits in loads using low power circuits such as light, television, etc. Nowadays, three phase has replaced the original two phase power systems for power transmission and utilization.
Three phase power contains either 3 live wires or 4 wires (3 phase wires and a neutral one), providing three alternating currents, separated in phase angle. The total loads are shared by the three wires. Most commercial buildings in North America use three-phase, four-wire power setups.
Figure 2: Three phase AC power
UPS System—Single Phase UPS or Three Phase UPS?
UPS units come in two different formats: single phase and three phase. The common phase configurations for UPS are shown in the following chart:
| Input | Output | Nomenclature | US Mains Voltage |
|---|
| 1 Phase | 1 Phase | 1/1 | 120/120Vac, 60Hz |
| 3 Phase | 1 Phase | 3/1 | 220/120Vac, 60Hz |
| 3 Phase | 3 Phase | 3/3 | 220/208Vac, 60Hz |
Single Phase UPS System (1/1)
As shown in the chart, single phase UPS has a single input and output of 120Vac (for Canada and the U.S.). A single phase installation consists of two wires where AC voltage is a single sine wave. The standard voltage of single phase varies in different countries or regions. The standard single phase voltage in America is 120V and Europe, Asia or other regions take 230V as a standard voltage.
Three Phase UPS System (3/1 and 3/3）
The three phase UPS can be subdivided into three phase input/three phase output UPS system and three phase input/single phase output system types. If you need to connect to a three phase supply, you must need a UPS with a 3/x configuration. A 3/1 UPS takes in 3 phase power but delivers single phase to the downstream load while a 3/3 UPS not only takes in but also puts out 3 phase power.
What's the Difference Between Single Phase and Three Phase UPS?
The key difference between single phase UPS and three phase UPS are the following points:
Conductor: The number of the conductor in single phase and three phase system is different. Single phase UPS contains one conductor while three phase UPS supply power through three conductors.
Sine wave: Single phase UPS provides a single sine wave, while three phase UPS provides three sine waves, each out of phase and spaced 120° apart from each other.
Voltage: Single phase voltage is 120V in North America, while the phase to phase voltage for a three phase system is 220V, and the phase-to-neutral voltage is 120V.
Maintenance: The plug and play characteristic of single phase UPS makes it easier than three phase counterpart to install and set up without the need for outside installation.
Efficiency: For low power requirements, single phase UPS is more efficient that three phase UPS. But when the demand for power is higher, three phase UPS shows more efficiency to carry a greater load in a safer manner.
Cost: The equipment in three phase UPS system will have longer life expectancies and the transmission lines for three phase power do not need the heavy gauge copper wires as single phase UPS, thus, in the long run, three phase UPS will save more money.
Application: Single Phase UPS units are available in those applications with lower kVA requirements, generally less than 20kVA, such as homes, small business and satellite offices. Three phase UPS units are commonly used in large installations, such as data centers, and large industrial power applications with higher power requirements.
How to Choose Between Single Phase UPS and Three Phase UPS?
Whether single phase UPS system and three phase UPS system should be chosen depends on the power needs of your applications as well as what power source the equipment is connected to. You will need to confirm the load the UPS will protect and access their voltage range. Generally loads less than 20kVA can safely use the single phase UPS, or larger loads tends to use three phase UPS. Once you deicides the 3-phase UPS, the downstream loads that the UPS protects will judge whether 3/1 UPS or 3/3 UPS is the most suitable one. If you are interested in how to calculate your UPS needs, you can further refer to How to Figure Out the Required UPS Capacity?
FAQs
With three times the power of a single-phase Uninterruptible Power Supply (UPS), 3-phase UPS is the most efficient way to deliver power to data centers or industrial applications for load levels typically higher than 10-20 kW.
What is the main difference between single-phase and three-phase? ›
The primary differences between single phase vs 3 phase AC are the consistency of power delivery and load capacity. The delivery of power in single-phase systems peaks and dips. Three-phase systems combine alternative currents in varying phases, which ensures that the power delivery never drops below the maximum.
What is a 3-phase UPS? ›
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.
Can a 3-phase UPS run on single-phase? ›
If a three-phase UPS is installed, it is possible to choose between 2 configurations: Three-phase UPS | Single-phase = Absorbs three-phase current and returns single-phase current; Three-phase UPS | Three-phase = It absorbs three-phase current and returns three-phase current to the loads.
How to tell if an UPS is 3-phase? ›
Single phase UPS contains one conductor while three phase UPS supply power through three conductors. Sine wave: Single phase UPS provides a single sine wave, while three phase UPS provides three sine waves, each out of phase and spaced 120° apart from each other.
Why choose single-phase over 3-phase? ›
The alternating current power supply can be classified into single-phase(1-phase) and three-phase(3-phase). In general, a single-phase power is used where electricity requirement is low. In short, it is for running small equipment. The three-phase power carries a heavy load and can run large machinery in factories.
Is 240v single-phase or 3-phase? ›
Single phase power has two wires; an active and a neutral. It supplies power at around 240 volts and is used in homes and businesses for most appliances and lighting. A three phase power supply has four wires; three actives and one neutral, and supplies power at both 240V and 415V.
What is the difference between single-phase UPS and 3-phase UPS? ›
With three times the power of a single-phase Uninterruptible Power Supply (UPS), 3-phase UPS is the most efficient way to deliver power to data centers or industrial applications for load levels typically higher than 10-20 kW.
What is a single-phase UPS? ›
The name, 'single-phase UPS', is due to having a single input and output source to the electrical equipment. Single phase UPS systems typically cover installations up to 20kVA and protect smaller devices such as servers, computer systems, telecommunications equipment and network devices.
Why would you want 3-phase power? ›
A three-phase circuit provides greater power density than a one-phase circuit at the same amperage, keeping wiring size and costs lower. In addition, three-phase power makes it easier to balance loads, minimizing harmonic currents and the need for large neutral wires.
To convert your system into single-phase, you can: Use a neutral wire: While it may not be as accurate as some of the other methods, using a neutral wire and ignoring the other two phases in the three-phase supply line can convert the system.
What is the UPS 3-phase input single-phase output? ›
UPS Three Phase | Single-Phase
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.
Can you split 3-phase into single-phase? ›
In a three-phase system, it is possible to split it into three separate single-phase circuits, which is not the same as a direct three-phase supply. If you see a fourth wire in the circuit, that will be a neutral wire, depending on what type of circuit you have.
What is a three-phase UPS? ›
3 Phase UPS: balanced, Efficient, Industrial Power
With three times the power of a single phase uninterruptible power supply (UPS), and load-balancing capabilities, three phase UPS are the most efficient way to deliver industrial backup power.
How do I know if I have single-phase or three-phase? ›
The simple way is to head out to your meter box, open it up and have a look. If you have three main switches or three fuse cartridges, you have three phase power. If you only have one, you have a single phase connection.
How to calculate 3 phase UPS load? ›
For three phase loads, the VA or kVA is calculated per phase and the largest number is then multiplied by a factor of 3 to calculate the UPS size required.
What are the benefits of 3-phase power at home? ›
The benefits of three phase power
Peak start currents are half the level needed for similar single phase motors — so less issues with power dips and flickering when a large motor is started, for example. Superior performance in a smart home, or a home where more appliances are being used consistently.
Can I run 3 AC on single-phase? ›
A common misperception is that air conditioners need a three-phase electrical connection. This is incorrect since the motors in all ACs are made to run on single-phase electricity. You may require a three-phase connection only if you have more than three air conditioners operating simultaneously.
Can I use a 3-phase breaker for single-phase? ›
According to UL's White book, "3–pole circuit breakers are suitable for use on 3-phase systems only, unless marked to indicate use on 1-phase systems, such as, “For 1–phase connections, use two outside poles,” or an equivalent statement.
Do I need 3-phase power in my house? ›
Reasons for 3 Phase
If you have a really big house with a large capacity air conditioner. If you want to have an Electrical Instantaneous Water Heater. If you are want are a DIY enthusiast and want to run a commercial size arc welder (Single Phase power should be OK for 275 Amps which is enough for 10mm steel.)
