Frequently Asked Questions

What is UPS (Uninterruptible Power supply) ?

An electrical device providing an interface between the mains power supply and load The UPS supplies sinusoidal AC power free of disturbances and within strict amplitude and frequency tolerances. It is generally made up of a rectifier/charger and an inverter together with a battery for backup power in the event of a mains failure.

What are the UPS topologies?


All three major topologies perform a basic level of power protection for computers and other sensitive electronics. Users who do not require the highest possible power availability to the critical load have options such as off-line or line-interactive UPS devices.

The off-line UPS is so named because the battery and/or the inverter are not supplying power to the load except when the utility "fails." The failure of the utility requires the switch to transfer to inverter. The inverter then starts and runs the load. The total transfer time after the command to switch is usually well less than a half cycle or eight milliseconds @ 60Hz and 10 milliseconds @50 Hz. The required decision and transfer time are usually acceptable for most electrical loads. Off-line, (also called stand-by), is a cost-effective choice for small, non-critical stand-alone applications, for example, isolated PCs and peripherals.

A well-designed line-interactive UPS utilizes the bi-directional inverter to perform two functions, namely to run the load and to charge the battery. As the name implies, the inverter "interacts" with the utility to maintain nominal output voltage to the load. An ability to interact with the utility supply improves the overall UPS performance over that of the off-line products. Line-interactive UPS devices offer protection against wide input voltage swings, sustained brownout and single-phase conditions. For many users, the line-interactive UPS represents a very good level of protection for a moderate investment. However, buyers should be aware that present line-interactive technology does not perform at the level of an on-line UPS.

True on-line UPS features an inverter that is on-line all the time, as well as a battery that is always in the energy power circuit and not separated from the inverter by switching means. The smooth, solid and repeatable performance of this topology yields a number of tangible benefits, particularly worthwhile for mission-critical applications. These include:

  • Superior battery life.
  • Superior line/load isolation, resulting in more stable output voltage.
  • Superior reliability with simpler controls and no switching required for battery operation.
  • Wide input voltage range which optimizes battery life and potentially reduces battery costs by up to 75%.
  • Assured reliable performance of the critical load by properly maintaining the required output voltage and providing more stable controls.


  • All major topologies -- off-line, line-interactive, on-line and hybrids -- work. The question is whether a given topology is appropriate for a given application. A true on-line UPS is most appropriate for truly mission-critical loads, or applications which require high availability. If on-line UPS performance is a requirement for the levels of availability expected of the computer/technology investment, then the UPS must be "on-line" in the traditional sense. When high reliability of electric service is required, switching between alternate energy sources is not acceptable.

    What is Backup time?

    Time during which the UPS can supply the rated load with nominal-quality power while the mains are down. This time depends on the battery and the efficiency of the UPS. Typical backup ranges from five minutes to several hours.

    What is Harmonics (current and voltage)?

    All alternating current which is not absolutely sinusoidal is made up of a fundamental and a certain number of current harmonics which are the cause of its deformation (distortion) when compared to the theoretical sine-wave.

    MTBF (Mean Time Between Failures)


    Calculation of the duration of normal operation of a repairable device between failures. The product, expressed in hours, is an indication on the reliability of the device.

    What is MTTF (Mean Time To Failure)?

    Calculation of the duration of normal operation of a non-reparable device, i.e. for which a MTBF is not possible. The product, expressed in hours, is an indication on the reliability of the device.

    What is MTTR (Mean Time To Repair)?

    Calculation of the time required to repair a device.

    What is Eco-Mode?

    The Eco-Mode function allows cost-effective operation of UPS Systems. In this operation mode, load is supplied by the mains. In the event of a mains failure, the inverter takes over the load and provides supply continuity to the connected systems.

    What are the advantages of IGBT rectifier UPS?

    Thanks to DSP controlled power factor corrected IGBT rectifier provides us higher input power factor, lower input current total harmonic distortion, wide input voltage and frequency tolerance. Inform UPS systems provide ≥0.99 input power factor PFi, and ≤ 5% input current total harmonic distortion THDi.

    High power factor helps you to consume less reactive power and pay lower electrical pay out. It provides minimizations of cable cross-sections, associated switchgear, transformer and generator sizing requirements.

    Low input current THDi avoids disturbance to other loads connected upstream the power distribution bus and interference reflected to the mains.

    What are the advantages of Intelligent Battery Charging?


    Considering the importance of the battery in a UPS system, Inform uses special technology to maximize the battery lifetime. It provides - charging voltage control according to temperature - protection against deep discharge - protection against over current - very low residual, ripple voltage - battery test with indication of battery condition.