Choosing the Right UPS

A UPS, short for uninterruptible power supply, is an electrical device that provides backup power when the power source fails.

A UPS is different from an auxiliary or back-up power system in that it provides almost instantaneous protection against power interruptions by supplying energy stored in batteries, supercapacitors or flywheels.

The run time of most UPS is relatively short (only a few minutes), but is sufficient to start an emergency (or auxiliary) power source or to properly shut down the protected equipment.

A UPS is typically used to protect computing equipment such as computers, data centers, telecommunications equipment and other electrical equipment when a power failure could cause severe service interruptions or data loss.

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  • How to choose a UPS?

    APC datacenter UPS

    In order to choose the right UPS to protect your equipment from technical failures, you will have to take into account various elements and ask yourself several questions:

    Why do you need a UPS?

    A UPS performs two essential functions:

    • Protecting electrical equipment from voltage variations and interruptions.
    • Stabilizing the electrical voltage and eliminating parasites.

    How much power does your equipment need to operate?

    Estimate the power requirements of all your equipment in order to correctly size your UPS. To do so, add up the power of all your devices (the power is expressed in VA).
    Tip: Favor a UPS with a power output of 20 to 25% higher than the total power of your devices, in order to have greater autonomy.
    For computer equipment, it is also important to take into account the power factor of the UPS (ratio between real power in watts and apparent power in VA). For example, servers have a power factor of 0.9.

    How much backup time do you need?

    Depending on your needs, you can choose your UPS according to its autonomy. In some cases, you may need to switch to a UPS system with backup battery for more autonomy.

    • There are 4 types of UPS:
      • UPS with 15 minutes of autonomy without a generator:
        • In 95% of the cases, power outages last less than 15 minutes, so with this type of UPS your appliances are 95% protected.
        • For example, you can save your data or stay online for up to 15 minutes before the system shuts down.
      • UPS with 15 minutes of autonomy with a generator:
        • The generator starts as soon as the power outage starts.
        • This configuration is particularly reliable and provides protection in most situations.
      • Redundant UPS with a generator and two feed lines for double conversion servers:
        • Expensive configuration.
        • Provides protection against all power failures.
      • UPS with battery have an autonomy of two hours or more:
        • When it is not possible to integrate generators, you will have to opt for a battery solution.

    Tip: install energy management software in cases where the duration of the power outage might exceed the autonomy of the UPS. This type of software allows you to save all your work in progress and accompanies the shutdown of all of your sensitive equipment.

    What is the voltage of your power source?

    • This depends on where you are located:
      • In North America the voltage is generally 120V or 208/240V.
      • In Europe and Asia, voltage is generally 230V.
    • Make sure that the input plug of the UPS matches the sockets of your power source.

    Where do you plan to install your UPS?

    • UPS come in different shapes and sizes, make your choice according to the space you have available:
      • There are rack-mount models that can be mounted in standard rack cabinets (height between 1U and 14U, U = rack space). They are suitable for confined spaces, i.e. for server and network applications.
      • For desktop applications or networked workstations, opt for the tower format (with the UPS placed upright on the floor, a desk or a shelf.)
      • There are also very compact desktop models. They can be used to protect computers, for example. They are more affordable than tower UPS but have a lower capacity.
  • What type of technology should you choose?

    There are 3 types of UPS:

    • Off-line UPS:
      • The devices connected to the off-line UPS are powered from the grid.
      • If the voltage drops below a certain threshold, the battery takes over and the UPS transforms the power into alternating voltage.
      • They have a power of 1kVA.
    • In-line (or line interactive) UPS:
      • These are off-line UPS equipped with a voltage regulator that enables them to switch to the battery in less than 2 milliseconds.
      • Their power ranges from 500VA to 5kVA.
    • On-line UPS
      • They produce alternating current continuously from the battery, which is itself connected to the mains.
      • Their power exceeds 5kVA.
  • Why choose an off-line UPS?

    EATON off-line UPS

    This kind of UPS is fairly affordable. They are suitable for office equipment, for example.

    However, in the case of a power outage, a few milliseconds without power can occur. They are therefore less reliable than other types of UPS.

  • Why choose an in-line UPS?

    Effekta Regeltechnik in-line UPS

    These UPS can switch to the battery in less than 2 milliseconds. This means they are very reliable and offer better protection than off-line UPS.

    They are suitable for sensitive equipment connected to networks where the voltage is unstable and subject to interruptions. They are also suitable for protecting computer servers in small businesses.

  • Why choose an on-line UPS?

    ABB on-line UPS

    This kind of UPS produces alternating current continuously. If the voltage at the input of the UPS drops, the battery stops being charged but the voltage at the output remains stable.

    On-line UPS are therefore particularly suitable for sensitive equipment that needs to be supplied with power at all times (such as servers in data centers, industrial installations or medical equipment).

  • What other criteria are important to consider when choosing a UPS?

    Energy efficiency and IoT are two new criteria to consider when choosing a UPS.

    • UPS in eco mode

    Like more and more industrial equipment, inverters are now available in eco mode.

    UPS consume energy even when they are at rest. To compensate for this, some manufacturers have developed a simple ECO mode by bypassing the UPS: the UPS continues to detect failures in real time, but is not able to supply energy immediately. It needs a few milliseconds before it activates and starts providing backup power. This type of ECO mode is therefore less reliable than a UPS that operates in the conventional way.

    Manufacturers such as Schneider Electric have developed UPS with an ECOnversion mode to solve this problem. These new UPS operate continuously so that when the power is cut off, they are already activated. There is therefore no time limit that would affect the charge.

    • Smart UPS

    With the development of the IoT, it is now possible to connect UPS, equip them with sensors and create entire smart electrical systems. This allows you to regularly collect data on the condition of the UPS and the electrical system, detect electrical problems before there is a power outage, and correct anomalies ahead of time.

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