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Understanding the Essential Function of a UPS: Providing Uninterrupted Power Supply

UPS stands for uninterruptible power supply and the name sums the device’s function up perfectly. It is an electrical device that provides emergency power to connected equipment when the regular power source fails. For most people, this means some form of interruption in the grid power. UPS units are commonly used to power computers, servers, networking equipment, and other sensitive electronic devices during power outages. They also protect equipment from fluctuations in grid voltage and frequency and other electrical disturbances such as spikes and dips in power.

 

What is the Main Function of a UPS?

The primary function of a UPS is to provide power to connected devices during power outages or when the input power falls below a certain threshold. This power is usually intended to operate for a relatively short duration while the grid is restored or the power quality from the grid improves. Sometimes, they are used to keep sensitive equipment temporarily powered while a generator is started. An uninterruptible power supply allows connected equipment to continue to operate without interruption or data loss.

UPS units typically include a battery or a bank of batteries that store electrical energy which can be delivered quickly when needed. In areas where the grid supply is reliable and stable, an uninterruptible power supply serves as a power conditioner, providing consistent, “clean”, power to the connected devices. It filters out voltage spikes, surges, and other electrical disturbances, protecting the equipment from potential damage.

Uninterruptible power supply units come in a range of sizes and capacities, ranging from small units designed for individual computers or home use to large-scale systems typically used in data centres and for critical infrastructure, such as medical equipment and military installations. Depending on the application and UPS type, they often have built-in features such as surge protection, voltage regulation, and automatic shutdown capabilities to safeguard connected devices. They are essential in environments where continuity of power supply is crucial, providing protection against power fluctuations, outages, and other electrical disturbances. They ensure the uninterrupted, reliable operation of connected electronic equipment.

 

Non-Battery-Based UPS Systems 

There are, however, non-battery-based uninterruptible power supply systems such as dynamic uninterruptible power supply systems used in large commercial operations housing sensitive electrical equipment. Such applications include server farms, data centres, medical facilities, military installations, and air traffic control environments. This technology is based on the storage of kinetic energy in a rotating flywheel (usually weighing several tons) connected to a dual-purpose alternator/electric motor.

When the power grid is functioning, the alternator operates as an electric motor powered by electricity from the grid. It spins up the flywheel, storing a significant amount of rotational kinetic energy. This stored energy is then used to power connected loads when power is interrupted. A diesel engine of suitable capacity then starts and turns the alternator, which transitions from motor to generator mode, providing power to the connected devices. When a power grid failure occurs, dynamic uninterruptible power supply systems seamlessly take over without any interruption. Notably, most of these systems do not rely on battery storage at all.

Supercapacitors may also be used as the energy source for an uninterruptible power supply. Supercapacitors are energy-storage devices that provide quick bursts of power. Energy is stored in capacitors and released during power interruptions. They offer high power density, as well as fast charging and discharging capabilities. They typically have longer lifespans than traditional batteries. Their energy-storage capacity is typically lower than battery-based systems, limiting them to short-duration backup power applications.

Fuel cell UPS systems are another alternative to batteries that generate electricity through an electrochemical reaction between hydrogen and oxygen. They use hydrogen as a fuel source and convert it into electrical energy in a non-combustion process. Fuel cell systems provide a continuous power supply while hydrogen fuel is available but require a hydrogen supply and suitable hydrogen supply infrastructure for operation. On the plus side, they offer high efficiency, low emissions, and long runtime.

 

Battery Based Systems

Battery-based UPS systems are the most widely used systems due to the unique characteristics of batteries that make them well-suited for handling significant changes in electrical current demand. These systems ensure a consistent voltage supply to an inverter, resulting in the delivery of clean and stable electrical energy to appliances. In terms of providing backup power during power outages, battery-based systems can be broadly categorised into three types: standby, line-interactive, and online UPS systems.

• Standby UPS systems are the most basic and cost-effective option. They operate by switching to battery power when the primary power source fails.
• Line-interactive UPS systems incorporate additional circuitry to regulate voltage fluctuations and protect against power surges.
• Online UPS systems, also known as full-time or double conversion systems, offer the most comprehensive protection. Incoming utility electricity is usually in the form of alternating current (AC), while batteries store direct current (DC) electrical energy. Therefore, a rectifier is necessary to convert the incoming AC electricity to DC for charging the batteries. Similarly, an inverter is required to convert DC electricity back to AC for powering most appliances, which contributes to the cost of these systems. Because electricity flows continuously through the rectifier and inverter, output voltage and frequency are completely isolated from the input. This creates voltage and frequency independent (VFI) devices, which effectively clean up fluctuations in grid voltage and frequency. Surge protection devices (SPDs) are typically incorporated to safeguard against harmful voltage spikes caused by lightning strikes or grid-switching on and off cycles. Furthermore, well-designed UPS systems will correct voltage sags or brownouts before they affect the output.

Online systems are typically more expensive and require more maintenance than the other battery-based systems, but full double conversion systems are best for sensitive equipment due to their high efficiency, instantaneous response, and clean power output.

 

Talk to the UPS and Power Supply Experts

With a legacy of exceptional service and technical excellence, our company, PacB, stands as a pioneering force in Southern Africa’s power-generation industry. We provide large-capacity industrial diesel generators as well as a comprehensive range of UPS and renewable energy systems. Our reliable MAKELSAN range of uninterruptible power supply systems are class leading and we have units to suit any size or type of application. We offer systems from 1 kVA to 800 kVA in size.

Contact us today if you need a UPS.