What is an Uninterrupted power supply and its functions?
   
  What is the difference between the UPS catagories: OFF-LINE, LINE INTERACTIVE, ON-LINE?
   
  Is UPS system really necessary for my computer?
   
  What exactly is meant by 'garbage' power?
   
  How does all this apply to my computer?
   
  How does an UPS eliminate these aberrations and give clean power?
   
  Is computers type of load some special category of load?
   
  How do I size my requirement?
   
  How does one select the battery?
   
  How long batteries last in a UPS?
   
  One of the batteries has failed in the UPS battery bank, is it alright to replace just one battery?
   
  How do I maintain and service the batteries and the UPS?
   
  How long can I leave the UPS switched off without damaging the batteries ?
   
  How do I know what to buy?
   
  What are the right steps to install Line- Interactive UPS?
   
  Which technology does Su-Kam use?
   
  There are other manufacturers of similar equipment. What is so special about Su-Kam systems?
   
  How cost effective is the investment in an UPS system?
   
  What type of topologies are employed in ON-LINE UPS configurations?
  Is Online UPS better?
   
  How do I install my Online UPS?
   
  What about After Sales Services?
   
  What is Load Crest Factor?
   
  What is Static Regulation?
   
  What is Dynamic or Transient Regulation?
   
  What is an Uninterrupted power supply and its functions?
 

An Uninterrupted power supply (UPS) is a system intended to solve the mains disturbances and mains failure. The batteries attached to the UPS enables the user to work during mains failure. This is done by putting the UPS between the mains and your computer.

 

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  What is the difference between the UPS categories: OFF-LINE, LINE INTERACTIVE, ON-LINE
  OFFLINE UPS
The OFFLINE UPS supplies (or routes) the incoming mains supply directly through to the output usually through a relay contact. Some high frequency noise filtering and surge suppression may be included in this path. The UPS switches on its inverter as soon as mains supply failure is detected or below the normal load and simultaneously switches the output relay to the inverter side to supply battery sourced power to the load. This transition involves a delay on account of the time to reliably detect mains failure and switch over a relay, and the output is broken for this period (usually for 2 to 12msec).
OFF - LINE UPS are usually the least expensive as compared to the other two.

The Block diagram of inverter is shown:

LINE INTERACTIVE
The true LINE INTERACTIVE design is in fact a combination of OFFLINE & ONLINE, in which the inverter plays a dual role of charging the battery when mains supply is present as well as regulating the output voltage and working as a normal inverter in absence of mains supply, so to the user it appears like an ONLINE System. Line Interactive UPS offers enhanced power protection over the basic Offline designs by providing additional line conditioning.

ONLINE UPS
An ONLINE UPS is the one in which the inverter always supplies power to the protected load and hence the same quality of power is ensured all the time. When mains supply is present, the inverter derives its power from thee mains supplied rectifier and the backup batteries are also kept in charged state. When the mains fail, the source of DC power for the inverter section shifts to the battery without any break whatsoever in the output to the Inverter. It also bears all the vagaries and noise borne out of the mains supply and insulates the secure bus supply from it.
An ONLINE UPS is especially useful for sensitive and critical equipments/devices.

 

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  Is UPS system really necessary for my computer?
 

 As an experienced & conscientious computer user, you have faith in the dictum GIGO and you take precautions to see that 'garbage' doesn't enter your system through software. But there is one more source of garbage, of a more serious nature, which is not normally taken care of. That is in the form of garbage power input to the computer. It is more serious because besides malfunctioning and operation problems it can also cause permanent damage to your computer.

 

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  What exactly is meant by 'garbage' power?
  It is common knowledge that there are fluctuations in utility supply .For example, some times the utility voltage is as low as 170 to 160 volts and high as 280 to 300 volts. Besides this, there are many more hidden culprits associated with utility lines like sags and surges, oscillatory transients, EMI and RFI, brown outs, or total loss of power.
 

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  How does all this apply to my computer?
  The equipment to which you are feeding this power is extremely sensitive to the quality of power and is termed as critical equipment. Imagine a sudden failure of computers during busy hours when a critical operation is in progress. All this can occur due to garbage power fed to such equipments. The loss is invaluable and you just cannot take any chances.
The above problem is of malfunctioning or operational nature. These can be extremely frustrating, time consuming and expensive. Besides, like all electronic circuits ,the computer circuits can also undergo irreparable damage due to high voltage surges and spikes, which can reach several kilovolts.
 

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  How does an UPS eliminate these aberrations and give clean power?
  The important blocks in a UPS and their functions are listed below: These shall be helpful in explaining the functioning of the UPS.
1) LINE FILTER : Eliminates line born noise and spikes.
2) INVERTER : The smooth DC is inverted by two transistors connected in push-pull configuration. The switching device (Transistor OR IGBT or MOSFETS) is used and controlled by a sophisticated control circuit.
A closed loop voltage feedback control is used to keep the output voltage constant even under widely varying DC voltage conditions. A proportional increase in the widths of the pulses causes an increase in voltage and a proportional reduction in width decreases the voltage. This means that the voltage control action is a great advantage for taking care of dynamic loading conditions in a computer like switching on and off of disk and tape drives as well as movement of the accessing head. A current feedback protects the inverter even from short circuit by turning off the control pulses going to the transistor / IGBT/ MOSFET base.
3) OUTPUT FILTER : The output filter converts the inverter output to a smooth AC with very low distortion. The nature of the filter is such that it can deliver inrush and surge currents demanded during switching on of computer loads.
 

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  Is computers type of load some special category of load?
 

Most certainly. A number of devices in various computer installations are studied, information is collected from device manufacturers and after taking all this into account the system is designed. Su-Kam has been doing this work in close co-operation with experienced people from computer application and computer maintenance fields. Therefore Su-Kam is in a position to offer its users a unique advantage over others.

 

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  How do I size my requirement ?
 

There are three ways in which we approach this.
Check the plate at the back of the equipment near the mains onlet. It will usually give a figure in watts(w) or Amps(A). If in Amps, multiply the line voltage by the figure given to arrive at a VA (Volt-Amp) rating add 25% which is what UPS are rated in.

 

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  How does one select the battery?
 

Battery selection depends upon the back up time required which in turn depends upon the frequency of power failure, average programme length and the presence of other back up source like a diesel generator set. One thing to remember is that the ampere hour ratings quoted by battery manufacturers are on a ten hour discharge basis and normally the back up time required will be much shorter; sufficient either to finish an almost complete job or to take a systematic shut down or to start the generator set. However, when the battery is discharged in a shorter time a derating factor has to be used which incidentally does not vary below 20 to 30 minutes. So approx half an one hour is a sensible back up time to select.

 

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  How long batteries last in a UPS?
  Battery life depends upon number of factors , viz.
- temperature
- number of discharges experienced
- number of deep discharges experienced
- specification of the batteries
 

Battery life is halved for every 10 degrees Centigrade temperature increase above it's specified operating temperature (usually 25 degree Centigrade).

UPS batteries are designed for maximum life in 'typical' use i.e. long periods of continous low charge and occasional minor discharges.

At installation time, the battery is at 100 percent of rated capacity. Each discharge and subsequent recharge reduces the relative capacity of the battery by a small percentage.The length of the discharge cycle will determine the reduction in battery capacity.
So-called deep discharges on a repeated basis will reduce the life of the battery.

The loaf of "bread" analogy is most often used to illustrate the relationship between cycling and battery life. A loaf of bread can either be cut into many thin slices or a few thicker slices. Similarly, a UPS battery can provide power over a large number of short cycles, or fewer cycles of long duration.

The IEEE defines "end of useful life" for a UPS battery as being the point when it can no longer supply 80 percent of its rated capacity in ampere-hours. The realationship between amp-hours and load protection time is not linear, a 20% reduction in capacity results in a much greater reduction in protection time. For example, a UPS battery that supports a full load for 15 minutes when new, will support the same load for only about 8 minutes when it reaches its defined "end of life".

When your battery reaches 80% of its rated capacity, the aging process accelarates and this is the time when the battery should be replaced.

No UPS battery will last forever - even one that experiences minimal use.This is because UPS batteries are electro-chemical devices whose ability to store and deliver power slowly decreases over time.So, even if you follow all the guidelines for proper storage temperature and maintenance, you still must replace them after a certain period of time.

 

 

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  One of the batteries has failed in the UPS battery bank, is it alright to replace just one battery?
  If the batteries are less than twelve months old then the failure could be due to a manufacturing or material fault. In this instance the failed battery can be replaced after confirmation by testing the whole battery bank.

In general once the batteries are over twelve months old, the failure is more likely to be due to age, environment or usage and the whole bank should be replaced. Failure to replace the whole bank could result in the new battery not being charged properly and your load being at risk if any or all of the older batteries fail.
 

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  How do I maintain and service the batteries and the UPS?
  Gradual decrease in battery life can be periodically monitored and evaluated by :
- Voltage checks
- Load testing
- Checking for proper battery connections
- Checking for battery water (in case of Automative batteries)

Without regular maintenance and service checks, your UPS battery may experience:
- Heat-generating resistance at the terminals
- Improper loading
- Reduced protection
- Premature failure or reduced backup
 

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  How long can I leave the UPS switched off without damaging the batteries ?
 

As long as the batteries are fully charged when the unit is switched off they will not require charging for three months.

Cold start feature of Power Pack Line Interactive UPS isolates the batteries from the UPS circuit and thus the UPS can be switched off for longer period (six months approx.) without damaging the batteries.

 

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  How do I know what to buy ?
  Following parameters should be considered before buying
- Company reliability, experience, stability, customer service.
- Technology and features.
- Price and performance.
 

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  What are the right steps to install Line- Interactive UPS?
  Recharge the UPS for at least 8 hrs before the first operation. Every UPS passes the quality examination before it is shipped out of factory. These QC parameters consumes the battery power of UPS. We strongly suggest users to recharge the UPS before using it at every first time to make sure that battery is in fully charged condition.
 

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  Which technology does Su-Kam use?
  Su-Kam is using the PWM Technology.The term PWM as used by us refers to pulse width modulation.

 

 

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  There are other manufacturers of similar equipment. What is so special about Su-Kam systems?
 

One is right when one says "similar". The reason is that the equipment manufactured by Su-Kam uses pulse width modulation technique with transistor/ IGBT/ MOSFET as the basic inversion element.There is no chance of the fuse blowing during sudden load application due to commutation failure. That means less down time and assured power supply. Due to PWM technique the size of the filter is also small which further improves the dynamic behavior.
We guarantee an inversion efficiency of more than 90 - 92% . High efficiency also results in smaller size. Our equipment is the smallest for a given rating, it occupies minimum floor space and can be installed very easily. A very generous design imparts tremendous short term overload capacity to our equipment which is essential to take care of large inrush and surge currents demanded by computer devices.

 

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  How cost effective is the investment in an UPS system?
  It is really quite simple. If you consider the average time lost & multiply it by the cost of computer time which you already know you will arrive at the direct loss. This, however, does not take into account indirect losses like job scheduling, trouble shooting, as well as corruption of files and damage to electronic circuits. If you take all these into account , definitely a Su-Kam system will pay for itself in less than one year.
 

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  What type of topologies are employed in ON-LINE UPS configurations?
  To satisfy the requirements of various applications and from the view point of criticality in operation, different topologies are employed in ONLINE UPS. The complexity and sophestication increases in ascending order.
HOT STAND TYPE CONFIGURATION

This configuration comprises of two units of UPS's (named UPS1 & UPS2). When UPS1 is delivering power to the load, UPS2 remains idle. In case of failure in the inverter of UPS1, static switch is enabled thereby providing uninterrupted power to the load through UPS2. UPS1 runs in synchronism with UPS2, ensuring no break transfer from UPS1 to UPS2. Under healthy conditions, the batteries get charged through their corresponding rectifiers.
PARALLEL REDUNDANT CONFIGURATION

UPS1 & UPS2 are paralleled together through a paralleling unit. The output load is shared equally (50%) by both the UPSs under healthy conditions. Both the UPS systems are synchronized with bypass. Upon failure of UPS1, the entire load is taken care off by UPS2 & vice versa. The bypass static switch is enabled only when the both UPS systems fail, providing immediate power to load. The batteries are independently charged through their respective rectifiers.
Truth Table:
b
Static Switch
Result
UPS1 & 2 healthy
OFF
Load is shared in equal propotion (50%) by both UPS.
UPS1 healthy & UPS2 trip
OFF
UPS1 handles entire load
UPS2 healthy & UPS1 trip
OFF
UPS2 handles entire load
UPS1 & 2 trip
ON
Load works on Bypass

CRITICAL NON-CRITICAL SYSTEM

UPS1 & UPS2 deliver power to the critical & non-critical loads respectively under healthy conditions. UPS1 synchronizes with UPS2 & UPS2 synchronizes with the bypass. In case of a critical inverter failure, critical load works on UPS2 through enabled STSW1, simultaneously transferring the non-critical load to Bypass by activating STSW3 & inhibiting STSW2. The restoration of the critical inverter will be responsible for retransferring the loads of their corresponding inverters. The batteries are charged through their corresponding rectifiers.
Truth Table:
b
STSW1
STSW2
STSW3
Result
UPS1 & 2 healthy
OFF
ON
OFF
Critical load on UPS1
Non Critical load on UPS2
Inv.1 trip & UPS2 healthy
ON
OFF
ON
Critical load on UPS2
Non Critical load on Bypass
Inv.2 trip & UPS1 healthy
OFF
OFF
ON
UPS2 handles entire load

 

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  Is Online UPS better ?
 

Online UPS provides better overall power protection to your computers and peripherals. This protection includes power conditioning, regulated voltage and frequency and zero transfer time to battery during mains failure.

 

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  How do I install my Online UPS?
 

Online UPS needs to be installed under supervision of a qualified technician.
Your supplier of JET Online UPS can install it for you.
Su-Kam also provides necessary assistance to your electrical contractor.

 

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  What about After Sales Services?
 

Every UPS needs to be serviced every 6 months to ensure its proper operation and battery condition.

We are proud of our reputation for customer service
We have a range of maintenance plans to suit every customer requirements from simpler repair to annual service contracts with guaranteed response time.

And every customer of Su-Kam has free access to our customer support.

 

 

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  What is Load Crest Factor?
 

A pure sine waveform has a peak value, which is 1.414 times the RMS value indicated on a voltmeter. A resistance or any linear load connected to such a voltage source draws currents having similar waveforms and hence has a crest factor of 1.4. As against this, the non-linear loads as described above may demand currents whose peak value to RMS ratios are 2 to 5 or more. This ratio of peak to RMS is termed as the crest factor, and is indicative of the degree of non-linear load handling capability of the UPS.

 

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  What is Static Regulation?
 

A regulated voltage source such as inverter section of ON-LINE UPS is expected to maintain the voltage at a predefined level, irrespective of changes in supply, 1.e. DC input voltage or load current levels. The percentage deviation of the output, as a result of load or dc input change, after the output voltage has settled to a new level is defined as the static or steady state regulation.

 

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  What is Dynamic or Transient Regulation?
 

The percentage deviation of the output from its steady state value immediately following a disturbance such as sudden change of DC supply voltage or load current is termed as dynamic/transient regulation. This deviation is generally much larger than the steady state value specified as voltage regulation, and incidentally is a measure of the speed of response of inverter control system. Since by defination this is a transient quantity, not only the deviation but the time to bring the voltage back to the steady state regulation level is also an important index of performance. Su-Kam's Online UPS have the Dynamic Regulation on Output voltage.

 

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