In parallel with the widespread use of technology and rapid development, clean energy needs are increasing.

UPS; Possible voltage fluctuations (crashes, uplifts, sudden changes) in the network where the electric load of the device (all devices operating with electricity) harmonics, short or long interruptions, etc. are electronic devices that protect the load from these changes and ensure that the load operates in a healthy and uninterrupted manner. UPS provides battery backup in these situations.


An Uninterruptible Power Supply is a device that sits between a power supply (e.g. a wall outlet) and a device (e.g. a computer) to prevent undesired features of the power source (outages, sags, surges, bad harmonics, etc.) from the supply from adversely affecting the performance of the device.


Uninterruptible power supplies have two functions against systems powered by electricity. The first is to protect the system against adverse network conditions. The other is to provide the user with time in order to complete the emergency operations in the system by transferring energy to the system for a period of energy that it stores during the power uninterruption. In short, it feeds electrical systems and corrects the abnormal conditions in the network, thus providing clean and high quality energy transfer to the system.


Small UPS systems provide power for a few minutes; enough to power down the computer in an orderly manner, while larger systems have enough battery for several hours. In mission critical datacenters,

UPS systems are used for just a few minutes until electrical generators take over.

UPS systems can be set up to alert file servers to shut down in an orderly manner when an outage has occurred, and the batteries are running out. Surge Suppression and Voltage Regulation A surge protector filters out surges and spikes, and a voltage regulator maintains uniform voltage during a brownout, but a UPS keeps a computer running when there is no electrical power.

UPS systems typically provide surge suppression and may provide voltage regulation.





Uninterruptible power supplies are used to protect important loads and keep them out of power. Receivers fed by uninterruptible power supplies operate with alternating current. The backup power of the uninterruptible power supplies is provided through the use of a battery. The 1-phase or 3-phase alternating voltage (AC) applied to the UPS input is converted to direct voltage (DC) with full wave rectifier circuits. During this turn, the voltage is both rectified and regulated. This correct voltage charges the battery. At the same time, this correct voltage is again supplied to the inverter via an alternating voltage via the inverter to provide a clean current receiver, fluctuations, harmonics, etc. at the mains input. is prevented. In the following way, it seems that the receivers are supplied with a clean current when the energy is not interrupted by the UPS.


In the event of interruption of electricity, the battery enters the circuit and the correct voltage stored in the battery is converted to alternative voltage via the inverter and delivered to the output. In this way, the receivers are not affected by the power interruption. The operating principle of the UPS is shown below in case of power failure.


UPS systems also have a bypass system. In case of a fault in the UPS, the input system voltage is not problematic and the system is supplied with the mains voltage. The operation is carried out with a transfer switch. As a transfer switch, a static transfer switch consisting of semiconductors (Thyristor, Triac) can be used as well as mechanical transfer switches. Feeding the receivers by bypassing the UPS is shown below.


The UPS also has surge protection devices. This prevents the overvoltages from damaging the rectifier, the charger, the inverter and the receiver. Again with the many filter circuits at the input and output, voltage fluctuations are avoided.

According to UPS structures are seperated to two as Static UPS and Dynamic UPS.

According to the working form of Static UPS are seperated to three as OnLine UPS, Line Interactive UPS, Off Line UPS.

All models are explained in detail below.


1. Dynamic Uninterruptible Power Supplies

Recently, with the development of semiconductor technology, static systems have begun to be used in conjunction with generators in places where very high power is required (such as 300-1000 kVA).

In dynamic type uninterruptible power supplies, there is a motor / generator at the output of static type power supplies. Since the output is the output of the motor, the sinus obtained is close to the ideal. Such power supplies are used in large industrial installations and critical applications.


2. Static Uninterruptible Power Supplies

2.1. Off Line UPS / Standby UPS:

The standby UPS is the simplest and least expensive UPS design. In fact, some don't even consider a standby UPS to really be a UPS, calling it instead a standby power supply (SPS). However, many of the most common consumer-grade devices marketed as UPSes, particularly on the lower end of the budget scale, in fact use this general design. They are sometimes also called offline UPSes to distinguish them from Online Ups In this type of UPS.

Stand-by UPSs are UPSs that receive power from the network at all times when there is a power source at the mains input, and the inverter only switches on when the mains power is turned off and the receivers feed. UPSs used for personal computers usually run in Standby mode. Below is a block diagram of UPSs running standby. When the transfer switch is in the up position, the mains voltage is filtered and delivered to the receiver. When the power is turned off, the transfer switch goes down and the receivers begin to feed on the battery pack and the inverter.

The characteristic of such devices is that they deliver the network directly to the load, under normal operating conditions. In other words, the load is nothing different from plugging into the mains socket.

However, when there is a power failure, the UPS begins to load the load from the battery. Therefore, the loads will not feel the power interruption. This technology, in which the mains voltage and frequency are transferred directly to the load, will feel a load all the distortions in the network.




2.2. Line Interactive UPS:

The line-interactive UPS uses a totally different design than any type of standby UPS. In this type of unit, the separate battery charger, inverter and source selection switch have all been replaced by a combination inverter/converter, which both charges the battery and converts its energy to AC for the output as required. AC line power is still the primary power source, and the battery is the secondary. When the line power is operating, the inverter/converter charges the battery; when the power fails, it operates in reverse. The main advantage of this design is that the inverter/converter unit is always connected to the output, powering the equipment. This design allows for faster response to a power failure than a standby UPS. The inverter/converter is also normally fitted with circuitry to filter out noise and spikes, and to regulate the power output, providing additional power during brownouts and curtailing output during surges. The line-interactive UPS is an improved design that is commonly used in units for home and business use. It is superior to the standby UPS, but it still has a transfer time, and thus does not provide protection as good as the Online Ups.

Unlike the offline UPS mentioned, the mains voltage is adjusted to some extent and transferred. There is no difference from off-line devices except this one.



2.3. Online UPS:

The online UPS, sometimes called a true UPS, is the best type you can buy. Paradoxically, it is both very similar to, and totally opposite to, the least-expensive type, the standby UPS. It is very similar to it in that it has the same two power sources, and a transfer switch that selects between them. It is the exact opposite from the standby UPS because it has reversed its sources: in the online UPS the primary power source is the UPS's battery, and utility power is the secondary power source! Of course, while seeming small, this change is a very significant one. Under normal operation the online UPS is always running off the battery, using its inverter, while the line power runs the battery charger. For this reason, this type of UPS is sometimes also called a double-conversion or double-conversion online UPS. This design means that there is no transfer time in the event of a power failure--if the power goes out, the inverter (and its load) keeps chugging along and only the battery charger fails. A computer powered by an online UPS responds to a power failure in the same way that a plugged-in laptop PC does: it keeps running without interruption, and all that happens is that the battery starts to run down because there is no line power to charge it. You may ask yourself, why bother having the secondary power path (the dashed line in the diagram above) if you are always running off the battery anyway? The reason is that this provides backup in the event that the inverter fails or stutters due to some sort of internal problem. While unusual, this can happen, and if it does, the unit will switch to the filtered, surge-suppressed line power. In this event, the matter of transfer time comes into play again, just as it does when a standby UPS reacts to a power failure. Of course, power failures are much more common than inverter failures. There is another key advantage to having the equipment running off the battery most of the time: the double-conversion process totally isolates the output power from the input power. Any nasty surprises coming from the wall affect only the battery charger, and not the output loads.






A UPS has internal batteries to guarantee that continuous power is provided to the equipment even if the power source stops providing power. Of course the UPS can only provide power for a while, typically a few minutes, but that is often enough to ride out power company glitches or short outages. Even if the outage is longer than the battery lifetime of the UPS, this provides the opportunity to execute an orderly shutdown of the equipment. Advantages: 


1. Computer jobs don't stop because the power fails. 

2. Users not inconvenienced by computer shutting down. 

3. Equipment does not incur the stress of another (hard) power cycle. 

4. Data isn't lost because a machine shut down without doing a "sync" or equivalent to flush cached or real time data. 

What sort of stuff does a UPS do?

A UPS traditionally can perform the following functions:

1. Absorb relatively small power surges.

2. Smooth out noisy power sources.

3. Continue to provide power to equipment during line sags.

4. Provide power for some time after a blackout has occurred.

In addition, some UPS or UPS/software combinations provide the following functions:

1. Automatic shutdown of equipment during long power outages.

2. Monitoring and logging of the status of the power supply.

3. Display the Voltage/Current draw of the equipment.

4. Restart equipment after a long power outage.

5. Display the voltage currently on the line.

6. Provide alarms on certain error conditions.

7. Provide short circuit protection.




There are two important situations in uninterruptible power supplies. These; the output voltage is the waveform and the efficiency of the UPS. Three wave types are obtained from the output of the inverter located in the structure of the uninterruptible power supply;

  • Sine Wave
  • Square Wave
  • Modified Wave




Sine Wave:

This is the best waveform, as it is the shape of an (ideal) AC electrical signal from the wall. The highest-quality UPSes produce a true sine wave output, which requires fairly expensive components in the inverter. This is especially important for online UPSes, since their loads are always running off the inverter. True sine wave UPSes are normally found only in higher-end models.


Square Wave:

The least desirable output waveform type, a square wave is sort of a "flattened-out" version of a sine wave. Instead of the voltage smoothly increasing from the negative maximum to the positive maximum and back again, it shifts suddenly from negative to positive, stays there for half a cycle, and then jumps to full negative and stays there for half a cycle, then repeats. Cheaper inverters are designed produce a square wave output primarily because the components required to do this are cheap. It wouldn't surprise you to learn that some equipment doesn't really like running on a square wave (it may be more surprising to learn that many types of equipment will run on it!) There are several reasons why square waves cause problems. For starters, the peak voltage of a square wave is substantially lower than the peak voltage of a sine wave, which causes issues with some types of equipment. In addition, while a sine wave has a single frequency in it--60 Hz in North America--a square wave contains many higher frequencies as well, called harmonics, which can cause buzzing or other problems with some equipment. Square wave output is found only in the cheapest equipment and should be avoided if possible.


Modified Square Wave:

This waveform is a compromise between the sine wave and the square wave. The positive and negative pulses of the square wave are thinned, separated and made taller, so the peak voltage is much closer to that of a sine wave, and the overall shape of the wave more closely resembles that of a sine wave. At the same time, the cost of the circuitry to produce a modified square wave output is much closer to the cost of a square wave's circuitry than that of a sine wave unit. (In fact, you can create a modified square wave by adding together two square waves that are shifted in phase slightly from each other.) Many fewer pieces of equipment have problems with modified square wave power than with straight square wave. Modified square wave output is used on many lower- to middle-range UPSes, and is also sometimes called "stepped approximation to a sine wave", "pulse-width modified square wave", or even "modified sine wave". The last term is marketing cutesy-speak, since the output form isn't really a sine wave, modified or otherwise.



The increasing use of electric energy and its application in devices and systems that require continuous operation at a vital place has brought about the problem of reliability of these energy generating resources.

AC networks, which provide more than 95% of the electricity consumed, are inadequate in today's applications, despite all the precautions taken for reliability, it is compulsory to feed the devices and systems which are considered as critical load through Uninterruptible Power Supplies (UPS).


AC power supplies are supposed to provide the following features:

• Provides an alternating voltage with constant effective value and constant frequency.

• Voltage wave shaped sinusoid.

• The energy supplied is continuous.

• These ordered features do not change with the loading style.


However, these features can not be found in practice. All the units from the generators in the power plants constituting the network to the supply terminals to which the consumer is connected,

provided limited features. The voltage effective value and the change in wave shape usually depend on the loading.

If the short-circuit impedance is not ideally zero, it will cause the voltage to change depending on the current drawn.

To keep the effective value constant, filter regulators can be used to correct the waveform.

Temporary failures at any point in the network also affect the consumer.

Disconnection of the power transmission line, opening of the circuit breakers in case of overloading, lightening of the transmission line, dropping and unloading of the transformers, short at tensions long

continuous interruptions are seen and the consumer can not feed on clean energy. In such cases, backup power sources such as motor-generator sets can be used.

However, since they are electromechanical converters, the duration of the interruption can not be reduced below a certain value. It takes a few minutes for the group to be automatically activated during the interruption and to be continuously regenerated.

It takes several hundred milliseconds for the grid to be continuously operated and the load to be transferred to the generator together with the interruption. But this is not economically efficient either.

Perhaps the most important problem faced by modern technology is that a number of electric powered devices and systems are affected even at very short intervals that can be seen in the feed.

Institutions such as hospitals, airports, and communication centers are getting less tolerant of interruptions.

For example, when an open heart surgery or transfer of necessary information to a plane during landing is interrupted, it is vital.


Mains failures affect the efficiency of industrial automation systems to a large extent. In the processes that demand continuity, the loss of material and workforce resulting from interruption are important dimensions.

Although there have not been any large-scale electricity failures in our country in recent years, short-term electricity energy interruptions sometimes can be experienced in regional maintenance works. Sometimes snow, rain, storms and floods, lightning on energy transmission lines can cause electricity interruptions in undesirable situations. High voltage stresses can also cause problems when energy is re-applied to the system through cutters at the end of power interruptions. If these precautions are not taken, electricity will cause power and financial loss. In such interruption situations, uninterruptible power supplies feed the buyers until the start of the operation of the generator systems.

The following are the areas of use of UPSs that are becoming increasingly widespread in industrial applications, whether they are vital organizations.


- Computers and computer aided automation systems,

- Computer aided manufacturing / packaging machines (automotive, metalworking, textile, etc.)

- Medical electronic devices, hospitals

- Airport lighting

- Air traffic control centers

- Military radar systems

- Communication and broadcasting organizations

- Elevators

- Electronic gates

- Barcode devices

- Writers

- Photographic printing devices (Minilab etc.)

- CNC Machine Tools

- Electronic scales

- Emergency lighting systems

- Heating equipment

- Refrigerators


These are the energy problems that are required to use the Uninterruptible Power Supply (UPS);





Spike is a sudden, dramatic tension in voltage; it may damage the device or completely destroy it.

They are high-amplitude, instantaneous events that can cause computer work or even damage equipment.

Spike can be caused by various reasons. The most important reason is near, far away or lightning transmission lines. Spikes can also be caused by sudden return of mains voltage.

They can cause big jumps in tension.


Other spike-forming events include the opening and closing of large electronic loads or the network and static discharge.

The most destructive event that can occur at the end of a spike is damage to equipment. The high voltage pulse can open holes in the microchip traces.

Sometimes this damage happens immediately; occasionally days may not show up for weeks.

Damaged data, printer, terminal or data processing errors are less dangerous results.

The equipment can cause very serious damage. It causes loss of knowledge.



Short-term increase in voltage. It will take at least 1/120 of your chance. We can say that a longer-lasting tension than a period.

The surge can result in a sudden stop or shutdown of a device on the line that draws a lot of power. The surge can occur when the mains switch large loads out of line.

Could be caused by very powerful electric motors such as air conditioners and running household appliances nearby. When these equipments are operated extra power is consumed in power lines.

Computers and other sensitive electronic devices are designed to receive power at a certain voltage range. Anything outside of the expected voltage will damage these appliances.

A surge is much more important than its size. Long or frequent surges can damage computer hardware.



Short-term reductions in voltage levels. It is the most common power problem.

The SAG is the opposite of surge. These are long low voltage conditions.

Grounding faults, weak power systems, sudden start-ups of large electrical loads are typical causes of voltage sags.

Start-up power requirements of motors, compressors, elevators, etc. are typical.

The collapse is also the way to deal with the extra power needs of the network.

Lightning strike is also an important cause of collapses. SAG, can pose a serious threat to computers.

The SAG can slow down the disc drive, cause reading errors and even crashes.

A SAG can deprive the computer of the power it needs; locked keyboards, and information loss that would result in system crash.

These collapses shorten the life of electrical appliances, especially electric motors.



Technically known as EMI (Electromagnetic Interferance) and RFI (Radio Frequency Interferance); electrical noise, inhibite desired sine wave.

It is a collective term used for various high-frequency impacts that ride on the normal sine wave. The amplitude can vary from a few mV to several V.

A particularly dangerous problem is the radio frequency (RF) noise.

Electrical noise is generated by many causes such as generators, radio transmitters, lightning strike, load switching and industrial equipment. Can be intermittent or chronic (continuous).

The RF noise consists of high-frequency signals circulating on electrical cabling.

RF noise can occur from lightning strike, radio transmissions, and computer power sources.

Noise can cause erroneous data transmission and computer processing, printer or terminal errors. It causes errors in programs and data files.


BROWNOUT is a long, undervoltage condition that lasts for minutes or even hours.

They are created by the networks when the peak current is above the capacitance.

Brownout causes logic circuits and disk drives to malfunction or damage hardware by depriving them of the required voltage for proper operation.



The mains power is completely lost.

There are 0 (zero) voltage conditions that occur for minutes, hours, even days.

They come to the energy distribution network more frequently as more and more load is placed on them.

Blackout can be caused by grounding faults, accidents and natural disasters.

The most significant impact is system crashes.

Excessive demand on the mains, lightning strikes, ice on transport lines, earthquakes are some of the reasons.

Disk drives or other system components may be damaged when power is suddenly interrupted.

Loss of memory (RAM) or cache memory can result in loss of hard-disk FAT resulting in erasing all information on the drive.



Normal sinus is a disorder that occurs in the wave. The harmonics are transmitted back to the AC line by non-linear loads.

Fax and copier machines, computers, variable speed motors are examples of non-linear loads.

These harmonics may prevent other devices connected to the AC line from operating. Harmonics can cause communication errors and hardware damage.

In three-phase systems, transformers and neutral conductors can overheat and create a fire hazard.




When an UPS is unable to protect and protect against a sudden loss of power, it is usually tested by pulling the UPS plug and seeing the result.

If the computer is still working, UPS will be suitable for this job.

In a test we did, this test is just a poor simulation of possible power failures. Some UPS brands give more response time than actual power misses in this simple "pull check" test.

This means that a UPS that has passed 100 times of the "pull check" test may not be able to protect your computer from a real problem.


The similarity between a plug-in test and a real power problem is that no voltage is applied to the computer in either case.

The main difference is that in the real power outage, other electrical loads on your building remain connected to the power line of your UPS.

The power draw of these loads is much higher than that of the UPS, and therefore they provide a short circuit at the input of the UPS. There is, however, a profound difference between the pull test.



Most UPS manufacturers use a reactive system that incorporates a backup power unit when a power failure is detected.

In the case of pulling the plug, the output of the UPS is immediately energized and the result is perfect. In the event of a real power problem, the backup unit is shorted to the point where it completes the transfer key motion.

Therefore, according to the plug pull test, an additional response time arises. In practice, this response time may increase from 20% to 50%.

Under certain conditions, a key arc can be created and the response to power failure may increase by half a period of 8 ms. As a result, the performance achieved using this system is not consistent.


Some manufacturers' UPS products use a different system. In their system, the UPS does not energize the backup power unit until it is certain that the "brains" transfer switch has completed its work.

In this structure, the backup power is never connected to the power input cable. The backup power is not switched on until the switch selects the backup power instead of the power input. Therefore, the reaction to real power problems is the same as the "plug pull check" test.



The table below shows which devices are suitable for which problems:



OnLine UPS

Off Line UPS

Line Conditioners







RF Noise


Common Mode Noisy









When the UPS is being purchased, it is necessary to perform power detection first. After power detection, it is useful to choose a UPS with a tolerance of 20% - 25% considering the future load increases.


If you have loads that are attracting sudden development currents for motor loads, the inrush currents need to be well determined. This prevents the overloading of the UPS during the first operation. In addition to making the appropriate power supply selection during the UPS purchase, it is also an important parameter to make the technical support of the device with a professional team. It should not be forgotten that the uninterruptible power supply is the first sale, as well as the after-sales service is even more important.



Generally, there are three different power detection methods that can be applied. It will be possible to perform power detection by selecting the most appropriate method for different systems.


1) Using the Power Chart:

Generally, this method is used to calculate the power of the systems that computer and computer peripherals create. For example, 10 Pcs 17 "monitor, 1 P4 server, 1 Laser (A4) and 1 Inkjet system power detection is as follows.

10 x 350 = 3500 VA

1 x 600 = 600 VA

1 x 700 = 700 VA

1 x 150 = 150 VA

Total: 4950 VA


The system calculated above is about 5kVA as it is about power. However, in situations like this, a power source that exceeds 20% of the calculated power can be proposed, considering the possible increases that may occur in the future. So the product for the above system will be 6 kVA.


2) Using Tag Values:

This feature can be used for power detection for feature medical devices and some small diameter industrial devices. The power is calculated by using the label on the product or the catalog information. There are 3 different power rating notifications on these labels that should be noted here. If the voltage (V) and current (A) values ​​are written, they can be multiplied to calculate the power (VA). If the power value is specified as Watt (W), this value is divisible by 0.7 and the VA value is dissipated.


3) By measuring:

The power detection of systems with large diameter industrial machines is done using special measuring devices.




Time during which the UPS can supply the rated load with nominal-quality power while the mains are down. This time depends on the battery and the efficiency of the UPS. Typical backup ranges from five minutes to several hours.

It is a matter of telling how long the loads will be fed by the energy stored in the batteries, which is used in uninterruptible power sources. The battery feed time is proportional to the number of batteries and the capacity (Ah). However, the UPS capacity is always stable. The only way to transfer capacity is parallelism, which is a way to increase reliability at the same time.



  • Achieving greater power from a single system, that is, increasing power.
  • Increase the reliability of the power source by allocating spare capacity for multiple devices.

There are three kinds of parallelism.

- Power Parallel

The goal is to increase power. Synchronous operation is based on logic. In this type of parallelism, two parallel devices behave like a single device. For example, if two UPSs with 100KVA are used, the total power is 200KVA.


- Redundent

The aim is to improve reliability by backing up. Synchronous operation is based on logic. Parallel running devices share the load. If there is a problem with some device, the other takes over the load. For example, if two UPSs with 100KVA are used, the total power is still 100KVA and it is not appropriate to overload the backup to avoid damage.


- Hot Standby

The aim is to improve reliability by backing up. It is used when synchronization can not be done. Under normal operating conditions, no load is placed on one of the devices (the backup one). If there is a problem in the other device (the original device), it enters the circuit and takes over the load.



The primary purpose of generator system as well as the UPS system is the same – to provide backup power. During power outages, the electronic devices are protected from damages and are able to work with such kind of alternate power resources. Yet, there are few major differences between the generator system and the UPS system that causes the dissimilarity in few of their applications.

Comparative Features of the Generator System:

It can be either portable or of the standby type; depending upon the size.

The working principle involves conversion of mechanical energy into electrical energy.

The reliability of the backup power mainly depends on sizing of the generator system.

There is a choice of either a manual switch or an automatic switch to turn on the generator system in case of power failure.

There may be emission of harmful gases during the course of its working.

Most of the generators produce unpleasant noise while in operation. The generator system provides backup power for a very long time. It also serves as an alternate power source.

Comparative Features of the UPS System :

The UPS system is most often portable, due to its smaller size.

The working principle involves conversion of the alternating current (AC) into direct current (DC); which is then stored as chemical energy in the batteries. This energy is further converted to DC which in turn is supplied to the device.

The reliability of the UPS system mainly lies on the proper functioning and operation of its battery.

Automatic switches are inbuilt into the UPS system to provide the immediate power backup in case any disruption or failure in the primary supply.

It is free from any kind of emission during its functioning.

The UPS system does not cause any disturbing noise while in operation.

The backup power offered by the UPS system is for a shorter duration. Most often it is enough to ensure the safe shutdown of the connected devices.

With the basic knowledge about the primary differences between the generator and the UPS system, it will be easier to make the choice that best fulfills your backup power needs.


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