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UPS, Source system

UPS, Source system

What is an uninterruptible power supply (UPS)?

Uninterruptible Power Supply (UPS) is an abbreviation for the English phrase: Uninterruptible Power Supply  which is understood as a continuous power supply system or more simply a backup power storage unit that helps increase the reliability of power supply for the system. system.

The application of uninterruptible power supplies (UPS) plays an important role in daily life, especially in today’s production business. Uninterruptible power supplies serve as an effective backup power source, operating continuously. continuously helps electrical equipment not be interrupted when a grid failure occurs.

Principle of operation

Many people already know that inside the UPS there will be a battery to store electricity, so just knowing that is enough to know the most basic operating principle of the UPS: Converting electricity from the battery to a power source. supply to the load when the input power supply to the UPS is lost.
Inside the UPS there is one or more batteries used to store electrical energy. Use a board that has the function of converting battery DC power into AC power, and this alternating current fluctuates in frequency and voltage to suit usage requirements.


  • Offline UPS: The operating principle of a standard Offline UPS is that the input grid power passes through the switching switch before being supplied to the load. The UPS now only uses the charger to fully charge the battery. In case the grid power is unstable (too high, too low or there is a power outage), the UPS will automatically switch (through a relay), using power from the battery to supply the device to maintain operation. UPS Offline does not Supports voltage stabilization function.

  • UPS Line Interactive: The operating principle of UPS Offline Line Interactive technology is similar to the standard UPS Offline line but has an additional voltage regulator circuit to regulate the output voltage supplied to the load to always be stable. In case the grid voltage is too high or too low, the voltage regulator circuit automatically switches to another step so that the output voltage ensures the correct load as required.
    Designed for use with office and computer equipment only; devices with purely resistive load properties. The slow switching time of the Offline UPS line is quite slow, about 10 ms and the power backup time cannot be extended with internal or external batteries.

  • Online UPS: The Online UPS line helps eliminate grid problems because the input voltage is always modulated before being supplied to the load. Mains power is not supplied directly to the device but is converted into direct current to charge the battery and inverter. The inverter will continue to convert the received DC current into an output voltage suitable for the device used. So it can be seen that when any problem occurs in the power grid, your equipment will always be safe. Online UPS lines are often designed with large capacity, and can extend battery backup time. Internal and external power storage, so in addition to purely resistive load devices such as office equipment and computers, UPS Online can also be used for server systems, data centers and even Even motor load equipment such as fans, pumps, etc.

How to choose between UPS Offline, Line Interactive or Online?

Determining usage needs, usage time and equipment capacity are criteria to consider to choose the appropriate UPS. For example, for a personal computer in the office or home, choose UPS Offline line. For server systems or data centers, UPS Online is the top priority.
Besides, if you need to extend the usage time to be able to complete the backup or shut down the system properly, you should choose a UPS that can be expanded with a backup battery (internal or external). In addition, some UPSs also have accompanying management software to help users monitor operating status and manage the UPS more flexibly and reliably when the mains power is lost.\

According to phase voltage

  • Single-phase UPS (1/1): Single-phase UPS has a single input and output of 120V (for Canada and USA). The standard voltage of a single phase varies in different countries or regions. The standard single-phase voltage in Vietnam is 220V.

  • Three-phase UPS (3/1 and 3/3): Three-phase UPS can be divided into three-phase input/three-phase output UPS and three-phase input/single-output UPS types. If you need to connect to three-phase power, you must need a UPS with 3/x configuration. A 3/1 UPS receives 3-phase power but supplies one phase to the downstream load while a 3/3 UPS not only receives but also supplies 3-phase power.

What is the difference between single-phase and three-phase UPS?

  • Conductors: The number of conductors in single-phase and three-phase systems is different. Single-phase UPS contains one conductor while three-phase UPS supplies 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.
  • Voltage: In Vietnam,  single phase voltage is 220V while 3 phase voltage is 380V
  • Maintenance: The plug and play feature of a single-phase UPS makes installation and setup easier than a three-phase UPS that must be installed externally.
  • Efficiency: For low power requirements, single-phase UPS is efficient

How to choose between single-phase UPS and three-phase UPS?

Choosing a single-phase or three-phase UPS system depends on the power needs of your devices as well as the power voltage to which the devices are connected. You will need to confirm the loads the UPS will protect and access their voltage range.

UPS, Source system