How to choose UPS power supply

For purchasers, most units and departments are configuring UPS for the first time and are still unfamiliar with the technology and its use and maintenance. Here are some opinions on how to evaluate the pros and cons of a UPS and how to reasonably configure the appropriate brand based on usage requirements.

Key points for consideration
(I) Electrical performance
1. Do not over-pursue the requirements for the conventional electrical performance indicators of UPS.
For example, the conversion time, voltage and frequency stability accuracy, waveform distortion, etc., the requirements for these indicators are not harsh for the load. In fact, the UPS of various brands currently on the market can meet the requirements of the load in these indicators. They should not be the key criteria for evaluating the quality, let alone the conditions for whether to select. As for the anti-interference ability, this is an indicator that must be possessed but difficult to detect. The user should examine whether there are high-frequency filtering links and configurations in the circuit structure of the UPS (including online type).
2. The requirements for the input power factor and harmonic current of the UPS should not be ignored.
Low input power factor and large harmonic components of input current mean interference and damage to the power grid, forming power pollution to the power grid, affecting the normal operation of other electrical equipment in the same power grid, and increasing the power capacity of other equipment and components in the power grid and power supply system. Especially for high-power UPS, they are usually dual-inverter online structures. Due to the rectifier circuit at the input end, their input power factor is only 0.8, and the harmonic current is as high as 25-30%. That is to say, if the active power introduced by the UPS from the power grid is 80 kilowatts, there will also be 60 kilowatts of reactive power flowing between the power grid and the UPS. This has a very serious impact on the power grid. If such a UPS is driven by a diesel generator, the power capacity of the generator needs to be 2.5-3 times that of the UPS.
3. Attention should be paid to the inspection of UPS output capacity and reliability.
The mean time between failures (MTBF) of UPS is only a parameter for estimating reliability. There are many factors that affect this value. It is an undetectable parameter. The various performance indicators of UPS output capacity are all quantifiable reliability indicators. Under the same operating conditions, UPS with high efficiency, large output current peak factor and surge factor, and strong overload capacity must have high reliability. This is an indisputable truth. In fact, compared with the actual power grid capacity, the above indicators are actually the restrictions of UPS on load, and the restrictions mean the lack of UPS capacity itself. Specifically, low efficiency means that the UPS itself has large losses and generates large amounts of heat, which will accelerate the aging of the main power semiconductor devices and reduce their service life. The low output current surge factor forces the UPS to switch to the power supply at the moment the load starts, and then switch back to the inverter power supply after the startup process is completed. This process has a conversion time and increases the probability of failure. The output current peak factor of only 3:1 is not enough. In order to meet the requirements of special loads, this factor should be increased to 5:1. As for the output power factor of 0.7 (capacitive), this means that when the load is purely resistive or inductive, the output capacity of the UPS is greatly reduced.
(II) Considerations from the perspective of reliability/availability
For UPS, the most important usage feature is undoubtedly the reliability of the UPS product itself. At the current stage of UPS technology development, the voltage/current output, conversion time, frequency stability and other parameters of various brands of UPS can all meet the needs of the computer equipment they carry. What users need to compare more is the reliability differences caused by the product quality and design factors.
Availability The fundamental goal of using UPS is to ensure that the user's equipment or load achieves the highest availability, that is, to ensure the uninterrupted operation of the system. Similarly, the availability of the UPS device itself has become the most important criterion for users to choose UPS devices. From the internal structure of the UPS, when the traditional UPS is working, on the one hand, it charges the internal battery or battery pack through the external power supply, and on the other hand, it also supplies power to the computer or other devices through the battery or battery pack. All batteries or battery packs are a whole for the UPS system, and there is no difference in function and use. When one of the batteries fails, the UPS management system cannot shut it down and replace it in time, but can only report the system failure, and then the management personnel will replace it manually. If the replacement and repair are not carried out in time, the power supply will be interrupted. When replacing the battery or battery pack, the UPS needs to be stopped, and the computer system supported by the UPS also needs to be suspended. Therefore, how to achieve the real uninterrupted operation of the UPS has always been a problem that has troubled the industry. In the traditional 6-20KVA medium-sized UPS products, there has always been a problem that a single UPS is prone to single point failure and the fault tolerance is lower than that of network components. The only safeguard is to purchase an extra UPS as a backup. There are two problems: the price is high, which is obvious, because you need to spend twice as much money to provide power protection for the same load; the other problem will be encountered when your system changes or expands, that is, it cannot be expanded. Redundant hot backup technology is an important way to ensure the availability of equipment, and choosing a redundant UPS system is the most effective way to solve the above problems.
(III) Comprehensive protection
Since enterprise-level users have high requirements for the availability of network systems, network systems need a comprehensive power protection solution, rather than simply being a "backup power supply". This protection solution should provide all-round protection based on power supply as much as possible under the principle of ensuring "uninterrupted power supply", such as eliminating grid noise, suppressing grid fluctuations, and preventing lightning strikes, and maximize the integration of technology or physical modules with other components of the information system to form an intelligent, layered and progressive three-dimensional protection network.
Corresponding to the four main components of the network, network power protection is also divided into four parts: power protection for key business servers, power protection for workstations and PCs, power protection for network interconnection devices, and power protection for data transmission lines. This strategy mainly has the following connotations:
1. For pure hardware, power protection is not the most important thing. What is really important is the protection of network availability.
2. Network systems are more complex, data requirements are more stringent, and the protection of key equipment is more important.
3. When designing a power protection plan, you should comprehensively consider the protection of key servers, workstations and PCs, network interconnection equipment, data transmission lines, etc., and optimize the power protection of the entire network. 4. When designing a power protection plan
, you should pay attention to the management of the power protection system. The relevant information can be transmitted to the operating system or network administrator through the network, which is convenient for remote management and saves time and money.

When purchasing a UPS power supply, the first few basic aspects worth considering are:
1. Technical performance;
2. Quality assurance;
3. Service guarantee;
4. Product price.

I hope the following brief description will be helpful to you in your purchasing process!

How to determine what type of UPS power supply you need? Usually, personal office and home users can consider backup models, such as Santak backup UPS power supply, which is low-priced and lightweight, and is an ideal partner for personal computers. It has a high cost-effectiveness; for network users, servers or precision instruments of small and medium-sized systems, online or online interactive UPS power supplies are often used, which can better resist various attacks from the power grid. They have complete functions and most of them have intelligent monitoring and network connection functions to achieve remote control and intelligent management. For large and important equipment and systems, high-power Santak online UPS is essential to provide stable power protection.

How do you determine the power (VA) required? You need to list all the devices that need to be protected, not forgetting the monitor, terminal, and external hard disk. The voltage and current data of each device can be found on the back panel. Multiply the two to get the VA value. Some devices use watts to indicate the power required. Multiply the wattage by 1.4 to get an approximate VA value. For the power of the entire device, use its rated number as the basis. Sum up the VA values ​​of all devices and add 30% of the expansion capacity to the total value in case of system upgrades.

How to configure the backup delay time of UPS power supply? Due to the differences in systems and equipment, the selected UPS power supply models and configurations are also different. According to the extended time, UPS is divided into two types: standard and long-term. The standard UPS power supply itself has a built-in battery, which can generally continue to supply power for several minutes to dozens of minutes after a power outage; while the long-term UPS power supply is equipped with an external battery pack, which can meet the user's need to continue to supply power during a long power outage. The backup time can be designed to be several minutes to more than ten hours or longer. Generally, the backup time of long-term UPS power supply is mainly limited by factors such as battery cost, installation space size, and battery recharge time. Generally, in areas with poor power environment and frequent power outages, UPS and generators are used to provide power. When a power outage occurs, the UPS is first powered by batteries for a period of time. If the power outage is long, the backup generator can be started to continue to supply power to the UPS power supply, and then switch to the mains power supply when the mains power is restored.

The battery power supply time is mainly affected by factors such as load size, battery capacity, ambient temperature, battery discharge cut-off voltage, etc. According to the delay capability, the required battery capacity is determined, expressed in ampere-hours (AH), and calculated by the number of hours of discharge time at a given current ampere.

The general UPS power configuration is calculated using the following formula:

UPS power (VA) × delay time (hours) ÷ UPS power startup DC = required battery ampere-hours (AH)
Take the 4-hour delay of Santak C3KS as an example to calculate: Note: The startup DC of Santak C3KS is: 96V
3000 VA × 4 hours ÷ 96V = 125AH

The result is that a 125AH battery is needed to provide 4 hours of power supply, but ordinary batteries are generally not available in a group of 8 with a capacity of 125AH (because the starting DC voltage of C3KS is 96V, and most ordinary batteries are 12V DC, 96V (UPS starting DC voltage) ÷ 12V (battery DC voltage) = 8, so 8 batteries are in a group)

Then, we can choose a set of 100AH ​​batteries to configure it:

The delay time is: 100AH ​​(battery capacity) × 96V (UPS start DC) ÷ 3000V (UPS power supply power) = 3.2 hours;

You can also choose to configure 2 groups (16 pieces) of 65AH batteries in parallel! The delay time is: 65AH×2×96V÷3000VA=4.16 hours

The standard starting DC voltage of Santak UPS when it leaves the factory:

MT1000S C1KS C2KS-C3KS C6KS-3C20KS 3C3-10KS--3C340KS
24VA 36V 96V 240V 384V

The voltage output power factor of Santak UPS power supply is 0.7: For example, the maximum supported load power of Santak C1KS is: 1000V×0.7=700W, so the maximum supported load of Santak C1K is 700W, and so on!! (Note: In order to better use the UPS power supply, we recommend that the UPS should not be used without load/full load or overloaded. The best load power of the UPS power supply is about 70%-80% of its standard load. For example, the best load of C1K is 500-600 (w) load! This can better play the advantages of the UPS power supply itself and extend the service life of the UPS power supply!)

When choosing a UPS power supply, you should first consider the actual use needs. You should analyze the required power capacity, load properties (capacitive load or inductive load), power supply mode (centralized power supply or distributed power supply), etc., and then decide which product to choose. Finally, make a comprehensive balance from the technical indicators, brand, price and after-sales service. The following is an explanation of several common computer users who need to be equipped with UPS power supplies. Other special users can also refer to the above principles to make their own decisions.

1. General individual users

The main purpose of using UPS power supply for general individual users is to prevent interference (surge, spike, overvoltage or undervoltage, etc.) in the mains from damaging valuable equipment such as computers, and to avoid the sudden power failure of the mains and the loss of their work results for a period of time. They also use relatively few devices, a computer, a printer, and perhaps a scanner, and there are not many opportunities for these devices to be turned on at the same time, so choosing a 500VA backup UPS power supply can fully meet the requirements, and the delay time does not need to be too long, 15 minutes is enough, during this time, you can calmly do the save work, and even work for a while. The 500VA backup UPS power supply is not large in size, cheap, mature in technology, fully sufficient and worth the money. If you use more equipment, and you are not sure about the backup UPS power supply in suppressing interference in the mains, and you have enough money, then you can consider buying an ordinary 1000VA online UPS power supply. UPS power supply with network function is really useless in your home. As for the brand, you should choose products with good after-sales service, easy installation and simple operation. Avoid pursuing too many fancy functions, which will only make you feel at a loss.

2. Small office users

We often encounter office environments like this, where several computers and a small number of external devices such as printers are used together. These computers are either connected to the network or used alone. In order to ensure the normal use and safety of all devices, UPS power supply is required. In this case, centralized power supply is often used, with low one-time investment and low maintenance costs. You can choose a 3000VA or 5000VA online UPS according to the number of devices. The online interactive type is also good, but it is larger in size and weight. The network function of the UPS power supply is not the key factor to consider here. The main consideration is that the product should be simple to install and operate, easy to use and maintain, and have necessary monitoring capabilities.

3. Internet users

Large network users may need to provide high-quality, highly reliable uninterruptible power supplies for multiple network servers, communication equipment and related precision equipment. At the same time, they need to install multiple UPS power supplies, and hope to centrally monitor and manage multiple UPS power supplies in the network like information network management, and have strict requirements for uninterruptible power supply. Such users should consider choosing large-capacity online UPS power supplies, preferably high-reliability UPS products designed for networks, such as APC's Symmetra power array, and require strong network functions for multiple operating systems and good power management capabilities.

Finally, I would like to remind you that the quality of the battery used in the UPS power supply and the quality of the charging circuit design are related to the life of the entire power supply. It is a crucial factor for UPS, but it is often overlooked by most users. Santak promised that it used better batteries to ensure a longer service life for the UPS, and APC's UPS power supply provides more comprehensive battery testing capabilities.