How to design an Uninterruptible Power Supply (UPS)?

Thread Starter

mdzhdhaka

Joined Sep 13, 2008
1
Hello there!
To build an UPS (off-line or on-line) is my BSc. Engg. project topic and tried a lot to collect the circuit diagram of UPS around 600VA (for supply voltage of 220V AC) but didn't find any good one to construct it.
It will be a great help to give any information about the circuit diagram of UPS or its major components such as inverter (pure sine wave or modified sine wave inverter, anyway, it will be great to find the multilevel inverter circuit), battery charger, control circuit.
I'll be ever grateful if any can give any reference.
 

SgtWookie

Joined Jul 17, 2007
22,227
I have yet to see a decent schematic published on the Internet for a UPS.

This is an area that's only marginally profitable for the manufacturers, and they jealously guard their schematics and theories of operation.

There are different types of UPS's. True UPS systems are continually online, generating the required output while their battery or batteries are constantly being recharged. There is a sacrifice of efficiency for this truly uninterrupible power supply.

The other type is a standby UPS; these keep the batteries charged, and constantly monitor the status of the line voltage. If there are power surges, sags, "brownouts" or other anomalies, the inverter section is brought online and the mains disconnected. There is a small time delay between the mains power anomaly and the inverter "kicking in". Some loads can tolerate this lag, and some loads cannot.

A typical mainframe computer installation would use a "true" UPS. They have better than 99.99% "up" time.
A typical home computer installation would use a "standby" UPS. They aren't as stable.
 

Tahmid

Joined Jul 2, 2008
343
Hi,
If you are planning to make a square wave offline UPS, the circuit would be pretty easy with discrete parts, but if it has to be modified sine or pure sine, use of microcontroller is necessary.
If you can give more details, I may be able to help.

Thanks.
Tahmid.
 

rajmehta

Joined Oct 17, 2008
1
Hi,
If you are planning to make a square wave offline UPS, the circuit would be pretty easy with discrete parts, but if it has to be modified sine or pure sine, use of microcontroller is necessary.
If you can give more details, I may be able to help.

Thanks.
Tahmid.

Yes, Exactly I completely agree with Tahmid. As per he said i made square wave UPS and believe me it was successful project from my school time.
Bye the share your experienced after complete it...
 

scubasteve_911

Joined Dec 27, 2007
1,203
Ionic,

The problem with that schematic is that it lacks source code for the micro, also, i couldn't find information on some of the transformers used.

Steve
 

karthik_dm

Joined Oct 16, 2008
27
Hello there!
To build an UPS (off-line or on-line) is my BSc. Engg. project topic and tried a lot to collect the circuit diagram of UPS around 600VA (for supply voltage of 220V AC) but didn't find any good one to construct it.
It will be a great help to give any information about the circuit diagram of UPS or its major components such as inverter (pure sine wave or modified sine wave inverter, anyway, it will be great to find the multilevel inverter circuit), battery charger, control circuit.
I'll be ever grateful if any can give any reference.
----------------

check out this inverter circuits,they produce square wave AC output from the 12v DC input from battery, to increase the wattage u hav to increase the transformer and driver transistor/mosfet current rating..the basic oscillator is common for all inverters u can also vary the output freq. by changing the sq.wave oscillator freq..set it to 50Hz..
 

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jblueink

Joined May 27, 2008
24
ionic,
pls can you help with the source code and the transformer rating of the inverter circuit you provide,atlist that will make the circuit more useful and helpful
 

karthik_dm

Joined Oct 16, 2008
27
thanks for your interest...
the circuits i have given are simple inverters. They are square wave oscillators. The square wave output feeds the driver transistors and switches them alternatively. i.e.,during +ve cycle the upper pair of transistor conducts and vice versa...so an alternate switching of transformer winding(primary) takes place. Then the 12v AC at primary is stepped up to 220v AC at secondary. They don't need any programming. If you prefer microcontrollers for switching in inverter then you have to write a program for generating square wave;some use PWM.....Transformer ratings depends on the wattage you need. for ex. if P=500 watts, then P=V x I. since V=220 volts, I=P/V
i.e, I=500/220.then the current I=2.27Amps. so you need a step up transformer with ratings of 220V/3amps at secondary end for 500W.There are transformers readily available. Or u take one from older UPs. for testing you may use a 12V-0-12v/8A step-down T/F by using its secondary as primary and pri. as secondary..
 
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