FAQs - On-line UPS

An online uninterruptible power supply (UPS) system is specifically designed to provide a continuous, reliable supply of electricity to your equipment, protecting it against power cuts and fluctuations. It works by converting incoming electricity from AC (alternating current) to DC (direct current), then back to AC before supplying your equipment. This process is known as double conversion, although some systems use triple conversion methods. As its name suggests, if the mains power fails, the UPS draws electricity from its batteries without interrupting the supply to your connected equipment.

UPS capacity is typically measured in VA (volt-amperes), kVA (kilovolt-amperes) or kW (kilowatts). The right size depends on how much power your equipment uses, how long you need battery backup to last and whether you plan to expand your installation further down the line (most businesses will at some point). Online UPS systems range from less than 1kVA to 1MVA or more, making them suitable for everything from small office networks to large data centres and industrial facilities. Our team can help you calculate your requirements and find the right product for your needs.

Single-phase uninterruptible power supply systems are commonly used to protect smaller IT installations, individual servers and office equipment. Three-phase systems are better suited to larger installations with higher power demands, such as those found in data centres and on industrial sites. Depending on the model, online UPS systems can support single-phase input and output (1/1), three-phase input with single-phase output (3/1), or three-phase input and output (3/3).

This depends on the battery type, operating conditions and how frequently the batteries are used. Standard valve-regulated lead-acid (VRLA) batteries with a 5-year design life will usually need to be replaced after around three to four years. Higher temperatures can shorten their lifespan, so keeping the surrounding environment at approximately 20–25°C all year round is important. Longer-life lead-acid batteries and lithium-ion alternatives are also available for certain UPS systems. Speak to us for more information.

Yes, Server Room Environments supplies replacement battery sets for compatible UPS systems, including batteries that you can install yourself (where manufacturers allow). We also offer a professional battery replacement service and will dispose of or recycle the batteries responsibly, recovering usable materials where we can.

A range of accessories can help you monitor, manage and maintain your UPS installation, like communication cards using SNMP or Modbus for remote monitoring; maintenance bypass switches that allow some systems to be serviced without interrupting the connected equipment; and power distribution units (PDUs) for distributing electricity to individual devices. Maintenance bypasses are available in wall-mounted and 19-inch rack-mounted configurations.

The term ‘double-conversion’ online UPS refers to the conversion of mains power supply AC (alternating current) by the rectifier/converter to a DC (direct current) to supply the inverter and charge the battery set. The inverter section to which the load is always connected ‘inverts’ the DC to AC. The AC-DC-AC process is described as ‘double conversion’. There is also a Triple Conversion online UPS mode for some designs covering AC-DC-DC-AC where the DC-DC is a converter.

An on-line double conversion UPS is a Voltage and Frequency Independent (VFI) uninterruptible power supply as defined by BS EN 62040. The inverter in this type of UPS produces a digitally generated sinewave output, supplied from a DC rectifier supply. The DC rectifier/converter supplies DC power to the inverter from the rectified mains power supply or the connected battery set.

The inverter section of an double or triple conversion online uninterruptible power supply is designed for continuous running and the powering of the connected load. This features allows the UPS to be connected to battery extension packs for long runtime applications up to seven hours or more. Some smaller online UPS may be restricted to 4hours on battery at full load in order to protect the inverter electronics from heat damage.

In an online UPS system the inverter section constantly powers the load during normal operation with a digitally generated AC (alternating current) sinewave supply and in almost all cases of a higher quality than would be achieved were the load to be connected directly to the mains power supply. The inverter is supplied with a DC (direct current) supply either from the front-end rectifier or battery set. This means that the UPS inverter receives either a supplier via the mains power supply (if present) or the battery set (if the mains power supply fails). The electrical capacitance built-into the inverter covers the almost instantanous transfer between DC power sources to ensure the inverter output is ‘no-break’ and truely uninterruptible.

Online UPS have a built-in automatic bypass. A circuit on the output on the inverter monitors the waveform for any signs of collapse either because of a short-circuit caused by an overload or fault condition. Such an event causes the automatic bypass to transfer the load to the mains power supply or alternative AC power source (such as a generator) to maintain load uptime.