What is an Uninterruptible Power Supply?
UPS Power Supply Explained
An uninterruptible power supply (UPS), also known as an uninterruptible power source, ensures continual power availability for your critical systems, even in the event of a mains power failure. Unlike standby generators, a UPS instantly switches to stored energy in its battery backup, providing seamless protection against power interruptions. With Delta's advanced range of online-double conversion UPS systems surpassing traditional options like the APC uninterruptible power supply, you can trust in reliable power backup tailored to the needs of the Irish market.
UPS systems are vital for safeguarding various equipment, including computers, data centers, telecommunications gear, and other electrical devices, against the adverse effects of power disruptions. They incorporate surge protection to shield connected appliances from voltage spikes, ensuring uninterrupted operation and preventing potential damage.
Whether you're looking to protect a single server rack or an entire data center, UPS systems come in a range of sizes to suit your requirements. In Ireland, where power reliability is essential, investing in UPS battery backup ensures peace of mind, mitigating risks associated with downtime, business disruption, or data loss.
Power Problems Solved with a UPS Power Supply
The primary function of any UPS is to provide short-term power when the input power source fails. However, most UPS units are also capable to varying degrees of correcting common utility power problems:
Voltage spike or sustained overvoltage
Momentary or sustained reduction in input voltage
Voltage sag
Noise, defined as a high-frequency transient or oscillation, usually injected into the line by nearby equipment
Instability of the mains frequency
Harmonic distortion, defined as a departure from the ideal sinusoidal waveform expected on the line
It's crucial to select a UPS not only based on its capacity but also considering the quality of power required by the connected equipment, thus avoiding potential issues with electric power quality. This approach ensures that your critical systems receive the reliable and stable power they need to operate smoothly.
UPS System Technologies
The three primary categories of modern UPS systems are online, line-interactive, and standby:
An online UPS employs a "double conversion" method, whereby it accepts AC input, rectifies it to DC for charging the rechargeable battery, and then converts it back to 120 V/230 V AC to power the protected equipment.
A line-interactive UPS keeps the inverter in line and switches the battery's DC current path from normal charging to supplying current during power loss.
In a standby ("off-line") system, the load is powered directly by the input power, and the backup power circuitry is only activated when utility power fails.
UPS units below one kilovolt-ampere (1 kVA) typically belong to the line-interactive or standby variety. These are generally low end UPS systems, typically utilised for personal computer and gaming systems.
Online double conversion UPS systems
In an uninterruptible power supply (UPS) system, the batteries remain consistently connected to the inverter, eliminating the need for power transfer switches. During a power loss, the rectifier simply disengages from the circuit, allowing the batteries to sustain a steady and unbroken power supply. Upon power restoration, the rectifier resumes its role in carrying most of the load and begins recharging the batteries, with the charging current potentially limited to prevent battery damage. The principal advantage of a UPS lies in its ability to establish an "electrical firewall" between the incoming utility power and sensitive electronic equipment, making it indispensable for safeguarding critical systems housed in server racks.
The UPS proves invaluable in environments where electrical isolation is vital, particularly in Ireland's power supply, or for equipment highly sensitive to power fluctuations. Once predominantly utilised in large-scale installations exceeding 10 kW, technological advances have made UPS systems more accessible, now available as common consumer devices supplying 500 W or less. UPS systems are indispensable in settings prone to electrical disturbances, frequent utility power fluctuations, or where protection of sensitive IT equipment loads is paramount. They are also essential for operations reliant on extended-run backup generators.
While the basic technology of a UPS mirrors that of standby or line-interactive UPS units, it typically incurs higher costs due to its significantly larger current AC-to-DC battery charger/rectifier and continuous operation design with enhanced cooling systems. Referred to as a double-conversion UPS, this design features the rectifier directly driving the inverter, even when powered by standard AC current.
UPS systems often incorporate a static transfer switch (STS) to bolster reliability, ensuring seamless power supply transitions in critical environments. Whether for a single server rack or an entire data centre, investing in UPS battery backup ensures uninterrupted operation and protection against power disruptions. View our range of Delta’s exceptional online double conversion UPS Systems.
Line Interactive UPS Systems
The line-interactive UPS operates similarly to a standby UPS, but includes a multi-tap variable-voltage autotransformer. This unique transformer can adjust the magnetic field and output voltage by adding or subtracting powered coils of wire. Alternatively, a buck-boost transformer, distinct from an autotransformer, may provide galvanic isolation.
This UPS type can withstand continuous under voltage brownouts and overvoltage surges without depleting the limited reserve battery power. Instead, it automatically selects different power taps on the autotransformer. Changing the autotransformer tap may briefly disrupt output power, potentially causing UPSs equipped with a power-loss alarm to momentarily "chirp".
This feature has gained popularity even in budget UPS units as it utilises existing components. The primary 50/60 Hz transformer used for converting between line voltage and battery voltage must provide two slightly different turns ratios: one for converting battery output voltage to line voltage, and another for converting line voltage to a slightly higher battery charging voltage. This voltage difference is necessary for battery charging. Additionally, switching on the line-voltage side of the transformer is easier due to lower currents.
To implement the buck/boost feature, two separate switches are required so that the AC input can connect to one of the two primary taps, while the load connects to the other, effectively using the main transformer's primary windings as an autotransformer. However, while "bucking" an overvoltage allows battery charging, "boosting" an undervoltage results in transformer output too low for battery charging.
Autotransformers can be engineered to cover a wide range of input voltages, but this complexity increases UPS cost. Typically, the autotransformer covers a range from about 90 V to 140 V for 120 V power, switching to battery if voltage exceeds or falls below this range.
During low-voltage conditions, the UPS draws more current than usual, potentially requiring a higher current circuit than standard devices. For instance, to power a 1000-W device at 120 V, the UPS draws 8.33 A. If a brownout occurs and voltage drops to 100 V, the UPS draws 10 A to compensate. Conversely, in an overvoltage condition, the UPS requires less current.
Offline UPS systems
The offline/standby UPS provides the most basic features, offering surge protection and battery backup. Typically, the protected equipment is directly connected to incoming utility power. When the incoming voltage exceeds or falls below a predetermined level, the UPS activates its internal DC-AC inverter circuitry, powered by an internal storage battery. Subsequently, the UPS mechanically switches the connected equipment to its DC-AC inverter output. Depending on how long it takes for the standby UPS to detect the lost utility voltage, the switchover time can be up to 25 milliseconds. The UPS is designed to power specific equipment, such as a personal computer, without causing any noticeable dip or brownout to the device.