Introduction to Uninterruptible Power Supply (UPS) Basics and Usage Precautions。

1、 What is uninterruptible power supply (UPS):

UPS, also known as uninterruptible power supply, is a system equipment that connects batteries (mostly lead-acid maintenance free batteries) to the host and converts DC power into mains power through module circuits such as the host inverter. 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 internal battery; When the mains power is interrupted (accident power outage), UPS immediately supplies 220V AC power from the battery to the load through inverter switching conversion method, so as to maintain normal operation of the load and protect the load software and hardware from damage. UPS equipment usually provides protection against high or low voltage.

2、 Composition of uninterruptible power supply UPS:

The UPS power system consists of five parts: main circuit, bypass, battery and other power input circuits, rectifier (REC) for AC/DC conversion, inverter (INV) for DC/AC conversion, inverter and bypass output switching circuit, and energy storage battery. The voltage stabilization function of its system is usually completed by rectifiers, which use controllable silicon or high-frequency switch rectifiers. They have the function of controlling the output amplitude according to changes in external power, so that when the external power changes (which should meet the system requirements), the output amplitude of the rectified voltage remains basically unchanged. The purification function is completed by the energy storage battery. Due to the inability of the rectifier to eliminate instantaneous pulse interference, there are still interference pulses in the rectified voltage. In addition to the function of storing DC energy, energy storage batteries are like connecting a large capacitor to a rectifier, and the equivalent capacitance of the energy storage battery is directly proportional to its capacity. Due to the fact that the voltage across the capacitor cannot suddenly change, the smoothing characteristics of the capacitor for pulses are utilized to eliminate pulse interference, which serves as a purification function and is also known as interference shielding. The frequency stability is achieved by the transformer, and the frequency stability depends on the stability of the oscillation frequency of the transformer. For the convenience of daily operation and maintenance of the UPS power system, system operation switches, automatic bypass switches after host self check faults, and maintenance bypass switches have been designed for switch control.

When the grid voltage is working normally, supply power to the load as shown in the figure, and at the same time, charge the energy storage battery; When there is a sudden power outage, the UPS power supply starts working, and the energy storage battery supplies the power required by the load to maintain normal production (as shown in bold black →); When the load is severely overloaded due to production needs, the grid voltage is rectified to directly supply power to the load.

3、 Working process of uninterruptible power supply UPS:

When the normal mains voltage is 380/220V AC, the DC main circuit has DC voltage, which is supplied to the DC-AC inverter to output stable 220V or 380V AC voltage. At the same time, the mains voltage is rectified to charge the battery. When the mains voltage is low or suddenly drops, the battery pack feeds electrical energy to the DC circuit through an isolation diode switch. There is no switching time from grid power supply to battery power supply. When the battery energy is about to be depleted, the uninterruptible power supply emits an audible and visual alarm, and stops the inverter from working at the lower limit of battery discharge, sounding an alarm for a long time. The uninterruptible power supply also has overload protection function. When an overload (150% load) occurs, it will jump to the bypass state and automatically return when the load is normal. When a severe overload occurs (exceeding 200% of the rated load), the uninterruptible power supply immediately stops the inverter output and jumps to the bypass state. At this time, the front input air switch may also trip. After eliminating the fault, simply close the switch and restart to resume work.

4、 Classification of uninterruptible power supply UPS:

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

Among them, the most commonly used is the backup UPS, which 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.

Backup UPS power supply is divided into backup sine wave output UPS power supply and backup square wave output UPS power supply.

Backup sine wave output UPS power supply: The single machine output can achieve 0.25KW~2KW. When the mains power changes between 170V~264V, it provides users with mains power processed by a voltage regulator; When the mains power exceeds the range of 170V~264V, UPS provides high-quality sine wave power.

Backup square wave output UPS power supply: Unlike backup sine wave output UPS power supply, it only provides users with 50Hz square wave power supply.

The structure of online UPS is relatively complex, but its performance is complete and can solve all power problems. For example, the CNKHZ series is characterized by its ability to continuously output pure sine wave AC power without interruption, which 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.

5、 Application areas of uninterruptible power supply UPS:

Uninterruptible power supplies are now widely used in mining, aerospace, industry, communication, national defense, hospitals, computer business terminals, network servers, network equipment, data storage devices, emergency lighting systems, railways, shipping, transportation, power plants, substations, nuclear power plants, fire safety alarm systems, wireless communication systems, program-controlled switches, mobile communication, solar energy storage and conversion equipment, control equipment and emergency protection systems, personal computers and other fields.

6、The advantages of uninterruptible power supply UPS:

The main advantage of an uninterruptible power supply is its uninterrupted power supply capability. When the AC input of the mains power is normal, UPS rectifies the AC power into DC power, and then inverts the DC power into stable and impurity free AC power for use by the downstream load. Once the AC input of the mains power is abnormal, such as under voltage, power outage, or abnormal frequency, the UPS will activate the backup energy - battery, and the rectifier circuit of the UPS will be turned off. Correspondingly, the DC power of the battery will be reversed into stable and impurity free AC power, which will continue to be used by the subsequent load. This is the origin of UPS's uninterrupted power supply capability.

Of course, the uninterrupted power supply time of UPS is not infinite, and this time is limited by the amount of energy stored in the battery itself. If there is an AC power outage, during the precious time of UPS battery power supply, what you need to do is to quickly restore AC power, such as using the backup AC power circuit or using the oil engine to generate electricity. If this is not possible, you can only save the work results and wait for the AC power to return to normal before continuing.

7、 Uninterruptible power supply UPS 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.

(3) The optimal output load control of UPS is around 60%, with the highest reliability.

(4) Overly light UPS load (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 turned 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 battery damage caused by excessive self discharge.