What Is a UPS System?

A UPS, also called an uninterruptible power supply system, is a device that ensures the load connected to it will stay on when the power goes off. It provides continuous and constant no-break power and is a continuous power solution, or CPS.

There are many reasons for a power failure occurring, including thunderstorms causing tripping of circuit breakers, damage to power lines due to falling trees, motor vehicle accidents, construction projects, ailing power grid, and bad power grid maintenance, to name a few.

In today’s techno fast-track world time is always money, so whether it’s your home PC, small office, large factory or hospital, your business and livelihood are at stake when the power goes off.

To prevent this it is essential to have a good quality reliable UPS system to bridge the power outage gap and allow sufficient time to systematically or automatically power down connected equipment in a controlled manner so as not to lose data or have damages OR to supply continuous, clean power to the critical loads until the alternative power generation source kicks in.

A good technology UPS not only ensures continuity of power when the lights go off (be it occasionally, or during the rolling blackouts that have been experienced over the last few years nationally in South Africa), it also ensures that the critical loads connected to the UPS’ inverter receive the best pure and clean Sinewave power that any sensitive load would need to operate correctly.

Clean vs Dirty electricity supply

The electricity supply from your municipality or ESKOM is typically very “dirty,” i.e. it is plagued with:

  • 1. Power dips (also called brownouts) are very short losses in power of less than one second, but which affect and corrupt data; leading to data failures in all types of systems from IT to software controls.
  • 2. Power failures (also called blackouts) are where the power fails for a few seconds, up to many hours or days. This often results in PC processors crashing and being damaged permanently.
  • 3. Power Spikes, or surges, are very high voltages for short periods which are caused when big circuit breakers on the power lines are switched on or off.
  • 4. Very high and low voltages experienced during the day as electricity usage increases and decreases in and out of peak periods.
  • 5. General dirty power that is introduced into the national power supply grid by significant electricity users such as mining and minerals where they use massive arc furnaces that can severely distort and affect the supply grid power quality.

An online double-conversion UPS system will prevent all of the above points, from 1 to 5, with NO effect from bad power in the supply grid on the loads connected to its inverter output.

UPS power supply sources

A UPS system makes use of two power supply sources. The first and primary power supply source is the mains supply, and the second power supply is from the battery, which forms an essential part of the UPS system and its backup power functions.

Under normal operation, the UPS will use its rectifier to charge the connected backup battery and at the same time supply power to the UPS inverter which, in turn, powers the load with good, clean energy of a superior quality to the standard mains power supply from ESKOM.

When the power fails, the UPS battery will instantaneously feed power to the UPS inverter, which will ensure continuous and uninterrupted power feed to the connected inverter loads.

At no time will the load ever feel the effects of any power supply irregularities, irrelevant of how quickly they happen or last.

The biggest factor is the available battery backup supply to the inverter. A backup battery is a finite source of power, i.e. it gets used up relatively quickly and cannot run for days on end.

Besides the filtering of power and ensuring clean power supply to the connected load, the main purpose of a UPS is to bridge the gap between when the power fails, and the backup generator starts.

Ensuring clean generator power

Another feature is that generator power is generally “dirty” power and varies all the time as loads such as air conditioners and refrigeration units kick in and out.

When they kick in the generator slows down in speed, and thus the voltage can drop from 220 VAC to, for instance, 180 VAC. The generator then settles at speed again after a few seconds and then supplies 220 VAC. Later, when they kick out, the generator over-speeds and the voltage can go as high as 250 VAC.

When an online double-conversion UPS system is connected between the generator/mains supply source and the critical load, the load connected to the UPS inverter will never “see” or “know” what has happened as the backup battery supply will ensure that the inverter stays on.

Most UPS systems use a generator/UPS combination as it is by far the most cost-effective backup power solution for extended power failures in excess of a few minutes and even rolling blackouts or power outages of several days.

Long-run battery back-up

A UPS can be fitted with a long run backup battery of several hours, but this is a lot more expensive unless you opt for the cheap, low tech products that are available for the household user. Unfortunately, in the long run, they prove unreliable and often have no after-sales service.

A long backup battery not only requires a technically competent person to calculate the size of the battery needed for daily outages, it is also very big in physical size, and all batteries have a limited usage life.

If a UPS battery discharges 100% two or three times a week, it will need full replacement in about 14 to 16 months.

The cost to replace it is enormous as it is the majority of the UPS system costs, being the most significant component thereof.

Over the service life of a UPS system with a long backup battery that is very regularly discharged, as happens in rolling blackouts, the battery will need replacement about 10 times over 15 years.

This expense thus makes the total cost of ownership HUGE for long run backup UPS systems that face regular power outages.

A generator/UPS combination is by far the most reliable and permanent backup power solution with a way lower total cost of ownership over 15 years than a long run UPS.

Three typical types of UPS systems

  • 1. Offline – CHEAPEST UPS SOLUTION/ WORST POWER QUALITY UPS
  • 2. Oline-interactive – A MIX BETWEEN THE CHEAPEST AND THE BEST
  • 3. Online double-conversion – BEST POWER PROTECTION, GUARANTEED PURE POWER USING LATEST AVAILABLE TECHNOLOGY

If the main and only reason for using a UPS is to back up on a power failure with a short switch-on time, so there is a very short power break that a PC will not see when it switches on, allowing time to shut down your home PC or small office appliances, then offline technology will work for you at a comparatively cheap price. These units do NOT supply a pure Sinewave output and are thus not suitable for use with certain loads. These units are typically only used to supply appliances with a built-in power supply like a PC, Decoder, most TVs, LED lights, etc.

If you want good quality clean and filtered power but can’t afford it and your loads are not affected by a very short switch-on time of a few milliseconds, then a line-interactive UPS is a trade-off between the best technology and the worst technology UPS systems. Some of the cheaper manufacturers use a low-quality inverter that doesn’t supply a 100% pure Sinewave; these units are typically only used to supply appliances with a built-in power supply like a PC, Decoder, most TVs, LED lights, etc. They do however provide some power filtering for dips and spikes in the mains supply, and thus the loads are partially protected from bad power in the power supply grid.

However, the ONLY way to supply a critical load, with clean, pure, filtered no-break Sinewave power under all types of mains supply quality and power outage conditions is the ONLINE DOUBLE-CONVERSION UPS system technology.

In Conclusion

UPS systems are used all over the world for millions of types of critical loads.

In buildings, mines, military, hospitals, data centres and factories, they supply uninterrupted power to many types of loads such as lifts, production processes, medical scanners and life support systems, emergency lighting, exit systems and many more.

Practically every electronic component and processor needs to be backed up by a UPS system to ensure its long term integrity and reliability.

No business can afford to lose hours of productive time: without a UPS, a company loses money.