An Overview Of How A UPS System Works

A UPS unit is an Uninterruptible Power Supply device that serves as a backup option when utility mains fail. It is also called an uninterruptible power source unit. A UPS has a flywheel or battery backup system to ensure it delivers emergency power during unexpected outages.

A UPS might seem to work like a standby generator or auxiliary power system but is distinctively different from the two. The UPS systems such as swl1850 provides instantaneous protection (or near-instantaneous) from power interruptions because it has one or more batteries and flywheels or special generators for the high-power user or electronic circuitry for the lower power user. It immediately switches to on-battery run-time for the smaller units when the utility mains fail, providing the user with roughly 5-15 minutes of electricity to help shut-down their machine properly, thus protecting them from data loss and electronic damage.

A UPS is not limited to protecting specific equipment. It can be used to protect data centres, computers, appliances, and telecommunication equipment that unexpected power disruptions can damage, or there could be data loss, business interruption, or injuries. UPS units come in different sizes. Some are small and practical, designed to protect a single computer (having a 200 VA rating). Others are massive units with a 300 kVA rating that can power a manufacturing process or 1 MVA rating that can power a data centre.

Different Types Of UPS Design

Modern UPS systems cone in three categories – standby/offline, on-line, or line-interactive.

  1. Standby/Offline UPS
    The system is directly powered by the input power having a battery-supported backup power circuitry triggered when the utility power fails. Many UPS units below 1 kVA use this setup and are mostly inexpensive standby/offline or line-interactive models.
  2. Line Interactive UPS
    The unit has an inverter in line and redirects the charging mode DC path to the battery, pull it from the battery to supply power during an unexpected outage.
  3. On-Line UPS
    It runs on a “double-conversion” system that pulls in AC and rectifies it to DC before sending the power to a rechargeable backup (one or more batteries), then inverts back to roughly 120V/240V AC that will power the attached equipment.

Other Variations

Dynamic uninterruptible power sources (DUPS) are ideal for supporting sizeable electric equipment. With this unit, a synchronous alternator or motor is linked to the mains via a choke. The incoming power is stored in a flywheel. And eddy-current regulation keeps the electricity when the mains supply fails. Sometimes, a DUPS is integrated or combined with a diesel-generator to create a DRUPS (Diesel Rotary Uninterruptible Power Supply).

Fuel cell uninterruptible power supply units were developed recently. They run on fuel cells and hydrogen to provide long run-times when powering a small space.

Standby/Offline UPS Design

A standby or offline UPS provides basic features. They have battery backup and offer sufficient surge protection for everyday power needs. The user’s equipment is connected to incoming power from the utility mains. The unit has the same voltage transient clamping setup used in the standard surge protected plugs strip that runs across the power line.

When the utility mains fail, the standby/offline UPS (SPS) evokes an internal DC-AC inverter system powered by an internal battery backup. The unit then switches the connected equipment to its DC-AC inverter output. The transition can occur within 25 milliseconds, depending on how long the standby UPS takes to detect the lost power from the mains.

Every UPS is designed to cover a specific range of equipment, depending on its load support capacity and the connected equipment’s sensitivity to voltage variations. For instance, the typical UPS unit that supports a personal computer can deliver the needed power without any noticeable disruption to the connected equipment.