Uninterruptible Power Supply (UPS): Why do you need one?

A UPS or an Uninterruptible Power Supply is a crucial device for those who want to protect their devices and have enough time to save their work and properly shut down their system. That would be the quick (and dirty) definition. Recently, in our Discord Server, we discussed electricity power issues. Being from Greece, I know firsthand that our power network is terrible, but I wasn’t aware of how bad it is in other countries, as well. For all those who have frequent brownouts and blackouts, a UPS is their best bet. This solution might save their system and valuable time, as well. But what is a UPS, and why should someone need one?

What is a UPS?

A UPS is a device relying to a considerable degree on batteries. These batteries feed the plugged-in devices with power when AC power is lost. There are three major UPS categories, which I will mention below.

Thanks to the Automatic Voltage Regulator (AVR)  circuits that most modern UPS include, power instabilities don’t require the UPS to fall into its battery mode when they are not too extreme. Moreover, you should keep in mind that not all UPS devices are suitable for your system, especially if you have a power-hungry one. It would be best to look into the maximum power they can handle, which is usually given in VA (Volt-Ampere). I won’t explain what VA represents since you can read that on Wikipedia.

UPS Types

Offline (Stand-by) UPS: This type of UPS device is the most basic and affordable. It doesn’t provide the best possible protection. Its batteries are not used while the incoming power is stable and within the specified limits. When the mains power is cut, or the incoming voltage level is below or above the predefined limits, the batteries are engaged to supply power to the plugged-in devices. This takes some time, usually from 4 to 25 mS. Offline UPS devices are not the best choice for PC systems.

Line-Interactive UPS: This is the preferable type for home users. They are a bit more expensive than the offline UPS but way more affordable than the third type. Like Stand-by UPS, their batteries are engaged when no power is present or the incoming voltage exceeds the specified range. The significant advantage of this type of UPS compared to offline ones is that they include an AVR circuit, allowing them to adjust the output voltage when the incoming voltage is changed to a degree. When the incoming voltage goes way out of range, and the AVR circuit cannot correct it, the batteries take the load and save the day. Depending on the output voltage, we have the more expensive UPS devices with pure (true) sine output and the less expensive ones with stepped or simulated sine. If you want to power a strong PC, it is highly preferable to get a true sine UPS, where the PF will be higher once the inverter circuit is in operation so that it can handle more load.

Online UPS: This is considered the best type. To cut you from the technical details, an online UPS feeds the plugged-in devices from its batteries the whole time, correcting at the same time any voltage input anomalies. This is why these UPS devices offer the best protection. Still, on the other hand, they are noisy because their inverter is constantly in operation, deplete the batteries faster, and consume more than the other two UPS types. This is why online UPS devices are generally preferred for servers and business applications.

Longevity of the UPS

Typically the most common problem is battery longevity. They usually last from 2-5 years, depending on the usage and their quality, of course. After that, you can buy a new UPS or replace the batteries. So, you should note if the batteries can be replaced and if you can do that alone. Purchasing a UPS that doesn’t require strong technical skills to replace its batteries is always advisable. Do note that you should never replace the existing batteries with larger-capacity ones because you will apply massive stress to the UPS inverter and probably damage it. The inverter in most UPS devices is designed for specific usage periods and not notably longer ones, else will fail.

For how long can a UPS supply power to my system?

This depends heavily on the load of the devices and the specifications of the UPS, among others. The specifications are usually written on the packaging or the manual of the UPS. This is where you should pay high attention to your system’s power consumption and the UPS VA rating.

True-sine vs. Stepped-sine Wave

Almost all UPS devices mention VA, which in a stepped-sine output UPS you can convert to Watts by dividing the VA by 0.6 (this means that we assume a PF reading of 0.6). So, if we have a 1000 VA stepped-sine UPS, the maximum load it can handle is about 600W. On the other hand, a true-sine 1000 VA UPS with a power factor of 0.9 and above can handle 900W loads. This is why you need to pay attention to the output of your UPS and prefer the more expensive true-sine ones.

How many sockets?

You should consider how many sockets you need and what type. UPS devices come with schuko or IEC sockets. So, if you need schuko, avoid IECs or vice versa. You can use adapters, but it is better to avoid them. You should also note which sockets provide full protection. In most UPS devices, only several sockets are connected to the battery, while the rest are only connected to the AVR circuit, so in case of a power cut, they won’t provide any power. Finally, it would be best to be extra careful when connecting power strips to a UPS, not to overload the specific socket.

Reviews

Unfortunately, there aren’t many proper reviews of UPS devices. The appropriate equipment costs a lot, and you must be highly experienced to use it. Crmaris of HWBusters has made some, and these are the most trustworthy. There would have been more by the HWBusters team, but no UPS OEM provided samples for review, and the cost of these devices is high, so HWbusters cannot cover it. APC (bought by Schneider Electric) and Eaton are well-regarded manufacturers but more expensive. Their higher-priced offers are worth looking for. For more affordable but decent products, look at Powerwalker and Cyberpower.

Epilogue

As you see, a UPS is a good choice if you experience electricity issues in your area. Please contact us through the comment section, our Forum, or Discord Server if you want advice regarding which UPS you should buy and why. We would be happy to assist you. Stay safe, and stay in the know.