UPS Inverter » What is an Inverter?



What is an inverter?
Technically, Inverter is a device, circuit or system that delivers AC power when energized from a source of DC power. In another words it can be stated that inverters change DC Power into AC power.

Practically, Inverter is a system, widely used in domestic domains, which provides back up power for the time when mains is not present. It takes DC from battery and converts it into AC & provides it to the household circuit, when mains is not present. But when mains is present it does the reverse, i.e. it takes power from mains AC, converts it into DC and charges the connected battery.

Today, everybody is familiar with the name inverter but as different categories of inverters are available in market, people get confused while choosing inverters. The categorization is made according to their feature, O/P waveform & Technology keeping in mind the proper operation of different types of loads.

Initially, there was quasi sine wave / square wave o/p inverter but these were not best suitable for inductive loads like fan, tube lights etc. But today advanced PWM technology inverter are in market, which produces pure sinusoidal waveform output, similar to domestic power supply, and suitable for all types of loads.

What is a UPS?
UPS Stands for uninterruptible power supply system. Since sensitive equipments & gadgets like computers require consistent supply of power of correct specification for their operation therefore they need an UPS. There are different types of UPSs.
1) Off line UPS
2) On line UPS
3) Line interactive UPS

Off line UPS – Basically, this UPS is similar to domestic Inverter described above, except, below given two differences.
1) The mains to battery changeover time or battery to mains changeover time in offline UPS is very low as compared to inverter. Typically, changeover time in inverters is 500 milliseconds & Offline UPS has changeover time of 3-8 milliseconds.
2) In a time, when mains ac is present, Inverter provides the output as is the input mains. While, Offline UPS has built in Automatic Voltage Regulator (AVR) to regulate the output voltage close to 220V ac. Now, there is some range of input voltage, which can be regulated, or in other words stabilized, by UPS. Normally, it is 150V to 270V. This means when mains input ac is between 150V to 270V, the AVR of UPS will regulate it to 220V, And when it is not in this range the system will shift to battery, so that the output remains uninterrupted.
Offline UPSs are normal weight UPSs and are widely used for domestic computers.



LINE INTERATIVE UPS: In this design, the battery to AC power converter (inverter) is always connected to the o/p of the UPS. Battery charging is done during times when the I/P AC power is normal when the I/P AC fails, transfer switch opens and then the inverter starts functioning to provide power to load immediately.



This UPS has the phase synchronization with input supply and the change over time is approximately 3 milli seconds.

ON LINE UPS: In this type of UPS, the system always remains on battery, whether mains ac is present or not. When mains ac is present, it provides power to DC supply of inverter section as well as charges the battery simultaneously. When mains ac is not present, it will run the connected load till the battery has a recommended dischargeable level.



So the change over time in ON LINE UPS becomes Zero because inverter section is always on. On Line UPSs are bulky and are manufactured in high capacity rating and used for larger & very sensitive applications like Servers, Medical equipments. These are much costlier as compared to offline or Line Interactive UPSs

FEATURES OF VARIOUS KINDS OF UPSs

FEATURES	NORMAL OFF LINE UPS	UTL LINE INTERACTIVE SINE WAVE UPS	ON LINE UPS
1) Change Over Time	5 – 8 msec.	3 –5 msec.	Zero
2) O/P Waveform	Quasi Sine Wave	Pure Sine Wave	Pure Sine Wave
3) O/P Voltage Regulation	200 – 245 V In Mains mode.	220 – 245 V in Mains Mode.	Always Constt. O/P.
4) Capacity Available	300VA – 2KVA	625 VA –3KVA	500VA – 30KVA
5) Dimension	Occupies Less Space	Less Space.	Needs More Space.
6) Application Criteria.	For Smaller Application Like Home PC etc.	Any application up to 3KVA	For Larger Application More Sensitive Equipments.
7) Battery Option.	Internal	Internal / External (Both) As Back up Required.	Internal / External (Both) As Back up Required.
8) Back Up.	Short Back Up Time.	Short / Long Back Up Options.	Short/ Long Back Up.

FEATURES OF VARIOUS KINDS OF INVERTERS

FEATURES	SMT INVERTER	SINE WAVE DIGITAL INVERTER	COMBO UPS
1) O/P Waveform	Quasi Sine Wave.	Sinusoidal Waveform So Total Humming Tree.	Quasi Sine Wave O/P.
2) Technology Used.	Advanced Hybrid SMT Technology.	Micro Controller Digital Technology.	Micro Controller Digital Technology.
3) Soft Start Facility.	Has No Soft Start Facility.	O/P Appears In Soft Start Mode.	At No Load Condition No Soft Start Mode But After Applying Load, O/P Appears In Soft Start Mode.
4) Over Load.	Auto Over Load Resetting But In Care, Load Is More Than 200% Of Rated Cap, Permanent Over Load Occurs Can Be Reset Manually Only	Auto Over Load Resetting But If Exposed To Excessive Load, Keeps on Beeping & Sensing The Load To Switch It Self On To Within Limit. If Load Not Reduced After 15 Such, Attempt, User Will Need To Start Manually.	Auto Quesload Resetting Just Like Sine Wave Digital Inverter.
5) Efficiency	95% Average.	95% Average.	95% Average.
6) Display	Led Display	LCD Display.	All Indications Are Led Display, Battery Level Continually Displayed On Front Panel.
7) Battery Option.	Any kind of unused batteries can be installed	Any kind of battery can be installed on UTL Sine Wave Digital Inverter.	Any kind of battery can be installed on UTL Combo UPSs.