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What is Uninterruptible Power Supply (UPS)?

Alan   utmel.com   2021-10-21 17:42:28

When the mains electricity input is normal, the UPS supplies the mains electricity to the load. At this time, the UPS is an AC motor, and it also charges the battery in the machine. When the mains electricity is interrupted (accident shutdown), the UPS immediately continues to supply 220V AC power to the load through the inverter switching conversion, allowing the load to maintain its normal operation and protecting the load and hardware. UPS devices typically provide protection for high voltage or high voltage.

Catalog

Ⅰ UPS Working principle
Ⅱ UPS Classification
Ⅲ UPS Development characteristics
Ⅳ UPS Precautions 

 

Ⅰ UPS Working principle

1.System composition

Figure 1,2

A typical UPS system block diagram, as shown in Figure 1. Its basic structure is a rectifier and charger that converts AC electrically converted to direct current, and the direct current is converted into an alternating inverter and the battery stores energy when the AC is supplied. Maintaining on a normal charging voltage, once the power is interrupted, the battery immediately powers the inverter to ensure the UPS power supply AC output voltage. Several of the following simplicity illustrates the various work conditions of the UPS (in an example of online UPS power).

(1) When power is supplied normally within the range allowed by the UPS, as shown in Figure 2, the thick line depicts the flow of power energy.

Figure 3,4

(2) After the main power failure, the main power failure is cut off, the power supply will instantly provide energy to the inverter as shown in Figure 3. 

(3) When the load is too large or the power supply inverter fails, the UPS will open the bypass by the main power supply directly, as shown in Figure 4.

2.Connection method

(1) A single UPS power supply can be supplied to all loads, connection pictures such as the system's schematic, and the connection method is simpler.

(2) The total load power requires two or more UPS power supply, as shown in Figure 5, this connection is called parallel.

(3) Two or more UPS power supplies have more intensity than the total load, but the system must be more than one UPS power supply capacity, and the rest can still be supplied when any UPS power failure. All loads are shown in Figure 6. This connection is referred to as a backup method.

(4) After the entire UPS power system is faulty, the main electricity is disengaged and directly on the load, and does not affect the maintenance of the UPS power system, which is shown in Figure 7.

(5) When the UPS power system is not faulty, the maintenance switch is opened, the input switch is turned off. When the UPS power system is faulty, the maintenance switch is closed, the input switch is turned on, and the output switch is opened. In this way, the normal operation of the electricity load is guaranteed but does not affect the online maintenance of the UPS power system failure.

3.Functions

With the increasing power requirements of the computer application, UPS is increasingly valued, and gradually develops a power protection system with regulated, stable frequency, filtering, anti-electromagnetic and radio frequency interference, anti-voltage surfing, and other functions. In particular, the line of the power grid and the supply of power supply are not too high, anti-interference technology is backward. The role of the UPS is more obvious.

The protection of UPS is first manifested to regulate the mains supply, and the input voltage range of the UPS is relatively wide. The general situation is from 170V to 250V, and the quality of the output power supply is quite high, and the rear-pre UPS output voltage is 5%. ~ 8%, the output frequency is stable at 1 Hz. As shown in Figure 1, the online UPS output voltage is stabilized at 3%, and the output frequency is stabilized at 0.5 Hz. When the main electricity is normal, the UPS power is equivalent to the exchange of electric motor regulators; while the mains is charged to charge the battery, and it is also equivalent to the charger. UPS automatically switches to battery-powered power, so that the computer is maintained normally and protects the hardware.

Ⅱ UPS Classification 

UPS is divided into the following three classes according to the new standard IEC (International Electrotechnical Commission) according to its structure and operational principles:

(1) Passive rear preparation UPS power supply

It refers to the inverter in the parallel connection between the mains and loads as a spare power supply. When the mains is normal, the load is complete. The inverter does not do any power conversion and the battery is powered by a separate charger. When the mains is absent, the electrical energy of the load is completely provided by the inverter.

Passive rear preparation UPS has the advantages of simple structure, the lowest price, which is used to use some non-important load usage, such as household computers. However, when the city is powered on, the relay switches the inverter to the load, the switching time is longer, and the interruption of several milliseconds is generally required, so a slightly important computer device should not use the passive rear pre-preparation UPS power supply.

(2) Online interactive UPS power supply

It means that the inverter is connected in parallel between the mains and loads, and the backup power is active, and the inverter charges the battery as the charger. Through the reversible operation of the inverter interact with the market, it is called an interactive. Such a UPS power supply, when the main electricity is supplied, the load is powered by the modified market, and the inverter is charged as the charger. At this time, the inverter functions as an AC / DC converter. At the time of failure, the load is completely powered by the inverter, and the inverter functions as a DC / AC converter.

Online interactive UPS has a simple structure, high efficiency, low operating cost, high reliability. It is convenient, easy to parallel, easy to maintain, performance meets some load requirements, especially for some computers in the network. The equipment is used in distributed power. Such power supply disadvantages are not high voltage regulatory performance, especially low dynamic response speed, and second anti-interference ability, circuit generate harmonic interference and modulation interference.

(3) Dual transform UPS power supply

The inverter is connected in series between AC input and load, and the power supply is continuously supplied to the load through the inverter. Such UPS power supply is as follows: When the main electricity is normal, the main electricity is powered by a rectifier; the inverter is powered to the load; when the market is absent, the electric storage appliance is powered by the inverter to the load. 

Dual transform UPS is the mainstream product of the UPS power supply. It has the advantages of good performance, high voltage stability and frequency stability, strong function, thermal backup connection, and parallel redundancy linkage. The deficiencies are less capacity 10kva or less, its machine is not high, generally around 85%.

Ⅲ UPS Development characteristics

(1)UPS uses modular online parallel expansion functions. At present, the UPS of the majority of high-power segments has already had redundant mesh. The UPS internal multi-module redundant parallel operation, and even multiple UPS composed of system redundant operation technology. In parallel transport, when a single module or single machine is faulty. The function is automatically turned to the redundant unit, which greatly improves the reliability of the UPS power supply system. 

(2) High efficiency, high reliability. Improve the UPS own energy efficiency, optimize load efficiency curves, reduce input current harmonics, and improve power factor.

(3) Digital, intelligentization of UPS.

(4) Green, energy-saving, and environmental protection of UPS. Energy-saving and environmental protection have become the guiding principle of technological innovation of UPS products. For UPS, the high and low of the input power factor indicates that its ability to absorb the power grid has a powerful power and an extent to which the grid is affected.

Ⅳ UPS Precautions 

Because of the particularity of its inverter and battery work, the installation and use of the UPS power must have a strict, scientific operation procedure to improve the working stability, reduce the equipment failure rate, and truly do uninterrupted equipment.

(1) The installation environment of the UPS power supply should avoid direct sunlight, and there is enough ventilation space to maintain the temperature of the working environment is not higher than 25°C. If the working ambient temperature exceeds 25°C, each temperature rise is increased by 10 ° C, the life of the battery will be shortened by about half.

(2) It is not advisable to use high-power thyristor load, thyristor bridge rectification, or half-wave rectification load, which is easily caused by the output of the UPS power supply, which is easy to cause the inverter to drive transistors being burned.  

(3) Strictly follow the correct boot, shut down sequence, avoid the voltage output of the UPS power source due to sudden increase or sudden decrease in the load.

(4) It is forbidden to frequently closing and turning on the UPS power supply. Generally requires at least 30 seconds after closing the UPS power supply to open the UPS power. Because the reason for the high-level failure of the small and medium UPS power supply is: User frequent boot or shutdown, the UPS power belt load performs inverter power supply and bypass supply.

(5) Practice prove: For the vast majority of UPS power, it is the best way to work within 50% to 60% rated output power range. Manufacturers suggest: The maximum start load of the UPS power supply is preferably controlled within 80%. If overloaded, in the inverter, it will often break through the inverter triode. It is not appropriate to overload operation, which is easy because the battery discharge current is too small to fail.

(6) Regular maintenance of the UPS power supply: Observe the status of the working indicator, dust removal, measure the battery voltage, replace the unqualified battery, check the fan operation and the system parameters of the detection of UPS.

(7) The UPS power is relatively suitable for micro-capacitive loads, not suitable for inductive loads, such as air conditioning, electric motors, electric drills, fans, etc. If the UPS power load is resistive or inductively loaded, the load must be reduced as appropriate to avoid overload operation.

When the mains electricity input is normal, the UPS supplies the mains electricity to the load. At this time, the UPS is an AC motor, and it also charges the battery in the machine. When the mains electricity is interrupted (accident shutdown), the UPS immediately continues to supply 220V AC power to the load through the inverter switching conversion, allowing the load to maintain its normal operation and protecting the load and hardware. UPS devices typically provide protection for high voltage or high voltage.

Catalog

Ⅰ UPS Working principle
Ⅱ UPS Classification
Ⅲ UPS Development characteristics
Ⅳ UPS Precautions 

 

Ⅰ UPS Working principle

1.System composition

Figure 1,2

A typical UPS system block diagram, as shown in Figure 1. Its basic structure is a rectifier and charger that converts AC electrically converted to direct current, and the direct current is converted into an alternating inverter and the battery stores energy when the AC is supplied. Maintaining on a normal charging voltage, once the power is interrupted, the battery immediately powers the inverter to ensure the UPS power supply AC output voltage. Several of the following simplicity illustrates the various work conditions of the UPS (in an example of online UPS power).

(1) When power is supplied normally within the range allowed by the UPS, as shown in Figure 2, the thick line depicts the flow of power energy.

Figure 3,4

(2) After the main power failure, the main power failure is cut off, the power supply will instantly provide energy to the inverter as shown in Figure 3. 

(3) When the load is too large or the power supply inverter fails, the UPS will open the bypass by the main power supply directly, as shown in Figure 4.

2.Connection method

(1) A single UPS power supply can be supplied to all loads, connection pictures such as the system's schematic, and the connection method is simpler.

(2) The total load power requires two or more UPS power supply, as shown in Figure 5, this connection is called parallel.

(3) Two or more UPS power supplies have more intensity than the total load, but the system must be more than one UPS power supply capacity, and the rest can still be supplied when any UPS power failure. All loads are shown in Figure 6. This connection is referred to as a backup method.

(4) After the entire UPS power system is faulty, the main electricity is disengaged and directly on the load, and does not affect the maintenance of the UPS power system, which is shown in Figure 7.

(5) When the UPS power system is not faulty, the maintenance switch is opened, the input switch is turned off. When the UPS power system is faulty, the maintenance switch is closed, the input switch is turned on, and the output switch is opened. In this way, the normal operation of the electricity load is guaranteed but does not affect the online maintenance of the UPS power system failure.

3.Functions

With the increasing power requirements of the computer application, UPS is increasingly valued, and gradually develops a power protection system with regulated, stable frequency, filtering, anti-electromagnetic and radio frequency interference, anti-voltage surfing, and other functions. In particular, the line of the power grid and the supply of power supply are not too high, anti-interference technology is backward. The role of the UPS is more obvious.

The protection of UPS is first manifested to regulate the mains supply, and the input voltage range of the UPS is relatively wide. The general situation is from 170V to 250V, and the quality of the output power supply is quite high, and the rear-pre UPS output voltage is 5%. ~ 8%, the output frequency is stable at 1 Hz. As shown in Figure 1, the online UPS output voltage is stabilized at 3%, and the output frequency is stabilized at 0.5 Hz. When the main electricity is normal, the UPS power is equivalent to the exchange of electric motor regulators; while the mains is charged to charge the battery, and it is also equivalent to the charger. UPS automatically switches to battery-powered power, so that the computer is maintained normally and protects the hardware.

Ⅱ UPS Classification 

UPS is divided into the following three classes according to the new standard IEC (International Electrotechnical Commission) according to its structure and operational principles:

(1) Passive rear preparation UPS power supply

It refers to the inverter in the parallel connection between the mains and loads as a spare power supply. When the mains is normal, the load is complete. The inverter does not do any power conversion and the battery is powered by a separate charger. When the mains is absent, the electrical energy of the load is completely provided by the inverter.

Passive rear preparation UPS has the advantages of simple structure, the lowest price, which is used to use some non-important load usage, such as household computers. However, when the city is powered on, the relay switches the inverter to the load, the switching time is longer, and the interruption of several milliseconds is generally required, so a slightly important computer device should not use the passive rear pre-preparation UPS power supply.

(2) Online interactive UPS power supply

It means that the inverter is connected in parallel between the mains and loads, and the backup power is active, and the inverter charges the battery as the charger. Through the reversible operation of the inverter interact with the market, it is called an interactive. Such a UPS power supply, when the main electricity is supplied, the load is powered by the modified market, and the inverter is charged as the charger. At this time, the inverter functions as an AC / DC converter. At the time of failure, the load is completely powered by the inverter, and the inverter functions as a DC / AC converter.

Online interactive UPS has a simple structure, high efficiency, low operating cost, high reliability. It is convenient, easy to parallel, easy to maintain, performance meets some load requirements, especially for some computers in the network. The equipment is used in distributed power. Such power supply disadvantages are not high voltage regulatory performance, especially low dynamic response speed, and second anti-interference ability, circuit generate harmonic interference and modulation interference.

(3) Dual transform UPS power supply

The inverter is connected in series between AC input and load, and the power supply is continuously supplied to the load through the inverter. Such UPS power supply is as follows: When the main electricity is normal, the main electricity is powered by a rectifier; the inverter is powered to the load; when the market is absent, the electric storage appliance is powered by the inverter to the load. 

Dual transform UPS is the mainstream product of the UPS power supply. It has the advantages of good performance, high voltage stability and frequency stability, strong function, thermal backup connection, and parallel redundancy linkage. The deficiencies are less capacity 10kva or less, its machine is not high, generally around 85%.

Ⅲ UPS Development characteristics

(1)UPS uses modular online parallel expansion functions. At present, the UPS of the majority of high-power segments has already had redundant mesh. The UPS internal multi-module redundant parallel operation, and even multiple UPS composed of system redundant operation technology. In parallel transport, when a single module or single machine is faulty. The function is automatically turned to the redundant unit, which greatly improves the reliability of the UPS power supply system. 

(2) High efficiency, high reliability. Improve the UPS own energy efficiency, optimize load efficiency curves, reduce input current harmonics, and improve power factor.

(3) Digital, intelligentization of UPS.

(4) Green, energy-saving, and environmental protection of UPS. Energy-saving and environmental protection have become the guiding principle of technological innovation of UPS products. For UPS, the high and low of the input power factor indicates that its ability to absorb the power grid has a powerful power and an extent to which the grid is affected.

Ⅳ UPS Precautions 

Because of the particularity of its inverter and battery work, the installation and use of the UPS power must have a strict, scientific operation procedure to improve the working stability, reduce the equipment failure rate, and truly do uninterrupted equipment.

(1) The installation environment of the UPS power supply should avoid direct sunlight, and there is enough ventilation space to maintain the temperature of the working environment is not higher than 25°C. If the working ambient temperature exceeds 25°C, each temperature rise is increased by 10 ° C, the life of the battery will be shortened by about half.

(2) It is not advisable to use high-power thyristor load, thyristor bridge rectification, or half-wave rectification load, which is easily caused by the output of the UPS power supply, which is easy to cause the inverter to drive transistors being burned.  

(3) Strictly follow the correct boot, shut down sequence, avoid the voltage output of the UPS power source due to sudden increase or sudden decrease in the load.

(4) It is forbidden to frequently closing and turning on the UPS power supply. Generally requires at least 30 seconds after closing the UPS power supply to open the UPS power. Because the reason for the high-level failure of the small and medium UPS power supply is: User frequent boot or shutdown, the UPS power belt load performs inverter power supply and bypass supply.

(5) Practice prove: For the vast majority of UPS power, it is the best way to work within 50% to 60% rated output power range. Manufacturers suggest: The maximum start load of the UPS power supply is preferably controlled within 80%. If overloaded, in the inverter, it will often break through the inverter triode. It is not appropriate to overload operation, which is easy because the battery discharge current is too small to fail.

(6) Regular maintenance of the UPS power supply: Observe the status of the working indicator, dust removal, measure the battery voltage, replace the unqualified battery, check the fan operation and the system parameters of the detection of UPS.

(7) The UPS power is relatively suitable for micro-capacitive loads, not suitable for inductive loads, such as air conditioning, electric motors, electric drills, fans, etc. If the UPS power load is resistive or inductively loaded, the load must be reduced as appropriate to avoid overload operation.

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