Uninterruptible Power Supply (UPS) FAQ.
1. Importance of UPS in our Life.
2. What is UPS.
3. Types of UPS’s.
4. Types of Power Problem.
5. Conclusions
UPS IMPORTANCE IN COMPUTERS / I.T EQUIMPMENT
Computers, network devices and communication equipment require additional protection against damages caused by irregularities in electrical supply, this protection can only be ensured by providing filtered and regulated electrical supply free from voltage fluctuations, noise, frequency distortion etc. Computer equipment cannot afford even a momentary power disruption. Any such problem will completely destroy data store in RAM and cache and at times may also damage permanently stored data on hard disk. They need a UPS to function smoothly.
WHAT IS UPS
A UPS is basically used with computers and work as contingent power supply. Generally UPS stands for "Uninterrupted Power Supply". It is basically used with computers and work as contingent power supply. The work doing on computers and the information stored in machine is perceived valuable, so it is not recommended to rely on a single power source. UPS consist of three main parts. One is inverter, which provides AC power through batteries in the absence of utility mains, other is charger, which recharges the batteries in the presence of utility mains and the third one is the battery bank.
It provides uninterrupted power during mains supply failure to the equipment connected as well as it protect the machine from several brown out conditions like surges, spikes, transients, frequency variations etc. It is considered too risky to work on computers without using UPS. This requirement made computers as biggest market for UPS though it is used with other IT equipment.
UPS TOPOLOGIES
There are significant differences between UPS products available in the market, with theoretical advantages for different applications. Nevertheless, the basic quality of design and construction is more dominant than topologies in determining the ultimate performance achieved in the user application.
Technologically UPS can be classified in two categories. One is 'Online' and the other is 'Standby'. Standby UPS is further divided into two categories. One is 'Off-line' and the other is line interactive.
STANDBY UPS
Standby UPS are those in which batteries are always lying on standby mode in the presence of utility mains. During mains supply UPS only filters input supply and charge the batteries by using its charger circuit. It provides power from the batteries by using the inverter circuit only upon power failure.
OFF-LINE UPS
This category of UPS consists of two separate circuits. One is 'charger' for charging batteries and the other is 'inverter for converting DC to AC. In Off-line UPS at any time only one circuit can be enable. Due to its design more hardware is required cause less reliability. So, this type of UPS are only recommended for less critical applications.
LINE INTRACTIVE UPS
In this category single circuit is used as inverter and charger. In the presence of mains this circuit provides additional filtering to reduce switching transients to the connected output. Upon mains failure this same circuit works in reverse mode and provide power from batteries. This circuit gives two main advantages, one is reduced changeover time from mains to batteries and the other is improved reliability due to less hardware involved. This technology is inherently work more efficiently to the standalone PCs as well as network applications.
ON-LINE UPS
This type of UPS is also known as double conversion UPS. In On-line UPS, the output power is always come through batteries. The charger circuit converts AC to DC to charge batteries and the inverter circuit again converts DC to AC to provide power to the connected load. On-line UPS provides ultimate protection, although these UPS are less efficient than the Line Interactive UPS. These UPS are recommended for data centers and other critical applications of this nature.
UPS can also be classified with respect to output waveform when it provides power from batteries. UPS's waveform must deliver the proper peak and RMS to the load, which is identical to the AC power. UPS produce three types of waveforms. Square wave, Step-Sinewave, and Sinewave.
SQUARE WAVE UPS
Square wave output delivers output with peak power identical to RMS power. This generates maximum noise due to harmonics and cause stress on components. Therefore, it is not appropriate to use with computers.
STEP SINE WAVE UPS
A simple Step-Sinewave generates less noise than square wave output while a regulated Step-Sinewave deliver proper peak and RMS values which is a good approximation of Sinewave. Therefore, regulated Step-Sinewave output is more appropriate to use with standalone PCs and other network applications.
SINE WAVE UPS
Pure Sinewave output is obviously an ideal waveform for any noise sensitive equipment. It generates no distortion on output therefore; it is most appropriate waveform for any computing system.
BATTERY TYPES
All UPS use batteries for power storage, which would use in the absence of mains supply. These batteries are usually lead-acid batteries. There are two types of batteries used in our local environment.
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SEALED MAINTAINENCE FREE BATTERIES
An international regulatory authority for UPS specify batteries where acid present in the form of gel and batteries are sealed therefore, requires no maintenance. Sealed battery UPS are the ideal solution for critical computing applications where backup power is more important than backup time. These batteries are renewed at around three to four years due to its better efficiency.
LEAD ACID BATTERIES
In this type of battery acid present in the form of mixture therefore require routine maintenance to keep them in working condition. Though, liquid batteries are inadequate to use in UPS, these are still used by most of the UPS manufacturers to provide maximum runtime economically to meet the local power conditions and buying potential. These batteries are renewed at around one to two years due to its less efficient operation.
POWER PROBLEMS
There are two unfortunate realities of the electronics age; the utility simply cannot provide the clean, consistent power demanded by sensitive electronic equipment, and the user is ultimately responsible for the health and safe operation of his equipment. Clearly, businesses are becoming more reliant on utility power supply that is pushed beyond its capacity. Unfortunately the situation won't be getting better any time soon.
With the increasing load and overload, power disturbances are also on the increase. It is well known that our national grid is overloaded and is working below the minimum required level for supply, leaving critical installations such as computer networks and telecommunications systems vulnerable to the damaging effects of reduced voltage. It is believed that 80% of all computer and electronics malfunctions are the result of power problems, the majority of which are in the form of sags, spikes and power line noise. Most fluctuations last 10 seconds or less, but can cause damage to hardware and lead to data loss or irretrievable corruption. The following is a glossary of common power problems:
SPIKES
Short bursts of high voltage on the main supply, often caused by network switching operations. Lightning strike is also a significant cause, generating spikes up to 3000 Volts.
Result: seriously fried kit!
TRANSIENTS
Low-amplitude, regular fluctuations in the supply waveform, caused by air conditioners, photocopiers, machine tools, lifts and other office equipment.
Result: component damage, memory loss, operating errors, program corruption.
BROWN-OUT
Watt Reduction in mains voltage, usually caused by high demand on the mains supply and typically occurring at peak times. This problem is becoming increasingly common on the national grid.
Result: Reduction in equipment performance, particularly speed, with possible damage to electric motors such as disk drives, CPU-Resetting - resulting in data loss, program files corruption, hard disk damage.
EMI/RFI
High frequency noise caused by the operation of arc welders, microwave radiation, broadcast transmissions and the noise caused by any electric motor due to commutators sparking. New EMI/RFI regulations have brought this problem into the spotlight recently.
Result: various faults in operation of equipment, for example data error readings on drives & monitor blanking.
SAGS /SURGS
Under- and over-voltage fluctuations caused by heavy equipment using the same supply, line faults, or generators.
Result: general wear and tear on equipment & possible damage.
DROP-OUT
Temporary cutout caused by faults on the electric network, switching operations or motors starting.
Result: general equipment malfunction, damage to hardware & data / program corruption.
Frequency Variations Caused by user's generators out of synchronization with the network.
Result: problems with disk drives and possible effects on logic and timing circuits.
POWER FAILURES
When mains supply fails, either through a power cut by the utility company or utility distribution fault or internally when a fuse or circuit breaker trips.
Result: Complete shutdown of systems with possible memory loss, long restart times after uncontrolled shutdown, corruption of data, general damage to the system. This does not have to happen! Many solutions are available to the user, ranging from surge/EMI filters to AC voltage stabilizers. For a better solution though you need an Unintruptible Power Supply (UPS) that can take care of most, if not all your power problems.
CONCLUSION
When power problems occur, which you will no doubt face sooner or later, the choice comes down to which UPS, not whether you should have power protection. There are significant differences between UPS products available in the market, with theoretical advantages for different applications. Nevertheless, the basic quality of design and construction is more dominant than technologies in determining the ultimate performance achieved in the user application.
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