What is UPS? Why use UPS?

UPS（Uninterruptible Power Supply）， Uninterruptible power supply is a system equipment that connects a battery (mostly lead-acid maintenance free battery) to a host and converts DC power into AC power through module circuits such as host inverters. The three basic functions of UPS are voltage stabilization, filtering, and uninterrupted operation. Mainly used to provide stable and uninterrupted power supply to single computers, computer network systems, or other power electronic devices such as solenoid valves, pressure transmitters, etc. When the mains power input is normal, the UPS stabilizes the mains power and supplies it to the load for use. At this time, the UPS is an AC voltage regulator and also charges the battery; Once the AC input of the mains power is abnormal, such as overvoltage, undervoltage, power outage, or abnormal frequency, UPS will immediately use the DC power of the battery to continue supplying 220V AC power to the load through inverter switching conversion, so as to maintain normal operation of the load and protect the load software and hardware from damage. The length of its power supply time depends on the capacity of the UPS battery and the power consumption of the load equipment. UPS equipment usually provides protection against high or low voltage. There are at least nine problems with the power grid: power outages, lightning spikes, surges, frequency oscillations, voltage transients, voltage fluctuations, frequency drift, voltage drops, and pulse interference.

Nowadays, UPS generally uses fully sealed maintenance free lead-acid batteries as energy storage devices, and the size of the battery capacity is reflected by the "ampere hour (AH)" indicator, which means the time for discharging according to the specified current. Batteries with the same voltage have a larger capacity with a higher ampere hour rating; Batteries with the same ampere hour capacity have higher voltage and larger capacity; The capacity of a battery is usually represented by both voltage and ampere hours, such as 12V/24AH, 12V/38AH, 12V/65AH, 12V/100AH, 12V/150AH, 12V200AH, etc. Batteries are an important component of UPS, accounting for a significant proportion of its value, and their quality directly affects the normal use of UPS. Therefore, it is important to carefully choose genuine batteries with quality assurance.

A、 The use of UPS

In the past, UPS was mostly used to assist computer equipment and prevent data loss caused by sudden power outages. Nowadays, UPS uninterruptible power supply has been widely used in mining, aerospace, industry, communication, national defense, hospitals, computer business terminals, network servers, network equipment, data storage equipment, emergency lighting systems, railways, shipping, transportation, power plants, substations, nuclear power plants, production factories, fire safety alarm systems, wireless communication systems, program-controlled switches, mobile communication, solar energy storage conversion equipment, control equipment and its emergency protection systems, personal computers and other fields.

B、 Classification of UPS

UPS is divided into three categories based on its working principle: backup, online, and online interactive.

Backup UPS has the most basic and important functions of UPS, such as automatic voltage stabilization and power-off protection. Although it generally has a conversion time of about 10ms, it is widely used in fields such as microcomputers, peripherals, POS machines, etc. due to its simple structure, low price, and high reliability.

The structure of online UPS is relatively complex, but its performance is complete, and it can solve all power problems with a conversion time of 0ms. For example, the four-way PS series has a significant feature of being able to continuously output pure sine wave AC power without interruption, and can solve all power problems such as spikes, surges, and frequency drift; Due to the need for significant investment, it is usually applied in environments with strict power requirements such as critical equipment and network centers.

Online interactive UPS, compared with backup type, has filtering function and strong resistance to mains interference. The conversion time is less than 4ms, and the inverter output is an analog sine wave. Therefore, it can be equipped with network equipment such as servers and routers, or used in areas with harsh power environments.

According to the condition of the equipment, the power environment, and the desired power protection purpose, a suitable UPS can be selected; For example, for low-power devices with built-in switch power supplies, backup UPS can generally be used. In places with harsh electrical environments, online interactive or online UPS should be selected. For devices that do not allow interruption time or require sine wave AC power at all times, online UPS can only be used.

C、 UPS is usually divided into two types: power frequency machines and high-frequency machines.

The power frequency machine consists of a thyristor SCR rectifier, an IGBT inverter, a bypass, and a power frequency boost isolation transformer. As its rectifier and transformer operate at a frequency of 50Hz, it is called a power frequency UPS as the name suggests.

High frequency machines are usually composed of IGBT high-frequency rectifiers, battery converters, inverters, and bypasses. IGBT can be controlled to turn on and off by controlling the drive applied to its gate. The switching frequency of IGBT rectifiers is usually between several K to tens of KHz, and even up to hundreds of KHz. Compared to the 50Hz power frequency, it is called high-frequency UPS.

D、 Procurement Key Points

1. Stability

Because UPS plays a protective role, its own stability is of utmost importance. So, when users choose UPS products, whether they are small and medium-sized enterprise users or others, they must first consider the quality of UPS products. Product quality is the first criterion for users to choose products. The reason why a brand is called a brand is because it has been verified and recognized by many people, and it is the most important factor.

2. Backup time

Backup time is a key indicator that many users pay attention to when purchasing UPS products, and it depends on the customer's needs. From an academic perspective, UPS is the continuation of power supply to equipment after a power outage. Firstly, this is a physics, and providing power after a power outage is only one of its functions. Secondly, its function is to ensure that users have a clean power source and protect their equipment from losses caused by it.

3. Determine the type of UPS

Determine whether to choose online, online interactive, or backup based on load requirements for output stability, switching time, and output waveform. The output stability and instantaneous response capability of online UPS are stronger than the other two types, and its adaptability to nonlinear loads is also stronger. For some more precise and important equipment, online UPS should be used. In areas with significant fluctuations in electricity supply, avoid using interactive and backup systems. If you want to use a generator with a short delay UPS, it is recommended to use an online UPS.

4. Service capability

The network characteristics and power environment of each user are different, and the requirements for power protection also change accordingly. Users may encounter various problems when using UPS, and they hope to purchase products and services that are completely suitable for their actual needs. They also care about the investment cycle, long-term return rate, and investment risks of the equipment. However, the reality is that the vast majority of users lack professionals in this field, so a high-quality service system and proactive service attitude have become important factors that users must consider when choosing UPS.

5. Attachment function

To improve the reliability of the system, it is recommended to use a UPS hot backup system, which can be connected in series or in parallel. Small capacity UPS (1~2KVA) can also use redundant switches. Remote monitoring panel can be selected to achieve remote monitoring and control of UPS operation. Monitoring software can be used to achieve intelligent management between computers and UPS. Network adapters can be selected to achieve network management of UPS (based on SNMP). In some rainy and thunderstorm prone areas, lightning arresters can be used. We also need to consider whether it is possible to protect the use of the network and external devices. As peripherals such as printers and scanners become increasingly complete, these devices also require protection. Do you have cable surge protection and data surge protection? Can automatic system shutdown be performed when there is no one on duty? In addition, because users often place their commercial desktop UPS next to them, the design style and manufacturing process of the product also need to be considered.

E、 Precautions

1.The usage environment of UPS should pay attention to good ventilation, facilitate heat dissipation, and maintain a clean environment.

2. Do not carry inductive loads such as cash counters, fluorescent lamps, air conditioners, etc., to avoid damage.

The optimal output load control of UPS is around 60%, which has the highest reliability.

4. Overloading of UPS (such as 1000VA UPS with 100VA load) may cause deep discharge of the battery, which will reduce the service life of the battery, and should be avoided as much as possible.

5. Proper discharge can help activate the battery. For example, if the mains power is not cut off for a long time, it should be manually disconnected every three months and discharged with a UPS load to extend the battery's service life.

6. For most small UPS systems, turn on the UPS during work and avoid starting it with a load. Turn off the UPS after work; For UPS in network rooms, as most networks work 24 hours a day, UPS must also operate 24/7.

7. UPS should be charged promptly after discharge to avoid damage to the battery due to excessive self discharge

F、 Usage and maintenance

1. Maintain a suitable ambient temperature. The important factor affecting the lifespan of batteries is the ambient temperature, and the optimal ambient temperature required by battery manufacturers is generally between 20-25 ℃. Although the increase in temperature improves the discharge capacity of the battery, the cost paid is a significant reduction in the battery's lifespan. According to experimental measurements, once the ambient temperature exceeds 25 ℃, the lifespan of the battery will be reduced by half for every 10 ℃ increase. If the environmental requirements cannot be met, there will be significant differences in the lifespan. In addition, the increase in ambient temperature will lead to an increase in the chemical activity inside the battery, generating a large amount of heat energy, which in turn will cause the surrounding ambient temperature to rise. This vicious cycle will accelerate the shortening of the battery's lifespan.

2. Regularly charge and discharge. The floating charge voltage and discharge voltage in UPS power supply have been calibrated to their rated values at the factory, and the magnitude of the discharge current increases with the increase of the load. During use, the load should be adjusted reasonably, such as controlling the number of electronic devices such as microcomputers. In general, the load should not exceed 60% of the rated load of the UPS. Within this range, the discharge current of the battery will not experience excessive discharge. Due to its long-term connection to the mains power supply, UPS batteries will remain in a floating charge state for a long time in environments with high power supply quality and rare mains power outages. Over time, this will lead to a decrease in the activity of the battery's chemical energy and electrical energy conversion, accelerating aging and shortening its service life. Therefore, it is generally recommended to fully discharge the battery every 2-3 months, and the discharge time can be determined based on the capacity and load size of the battery. After completing a full load discharge, charge for at least 8 hours according to regulations.

3. Utilize communication functions. Most large and medium-sized UPS systems have operational capabilities such as communication with microcomputers and program control. Install the corresponding software on the microcomputer, connect the UPS through the serial/parallel port, run the program, and use the microcomputer to communicate with the UPS. Generally, it has functions such as information inquiry, parameter setting, timing setting, automatic shutdown, and alarm. Through information retrieval, information such as the input voltage of the mains, the output voltage of the UPS, the load utilization rate, the battery capacity utilization rate, the temperature inside the machine, and the mains frequency can be obtained; Through parameter settings, basic characteristics of UPS, battery maintenance time, and battery depletion alarm can be set. Through these intelligent operations, the use and management of UPS power supplies and their batteries have been greatly facilitated.

4. Replace waste/damaged batteries in a timely manner. The number of batteries equipped with large and medium-sized UPS power supplies ranges from 3 to 80, or even more. These individual batteries form a battery pack through circuit connections to meet the needs of UPS DC power supply. In the continuous operation and use of UPS, it is inevitable for individual batteries to experience performance degradation and storage capacity failure due to differences in performance and quality, resulting in damage. When one or more batteries in the battery pack are damaged, maintenance personnel should inspect and test each battery to eliminate the damaged ones. When replacing a new battery, one should strive to purchase batteries from the same manufacturer and model. It is prohibited to mix acid resistant batteries, sealed batteries, or batteries of different specifications.