I liked the bit about IC engine and car. well explained

UPS ( Un interrupted Power Supply ) as the name suggests provide power to your load continuously even when the mains fail.This consists of a voltage step down transformer, rectifier and filter circuit, battery backup, inverter and harmonic filters.

Since the output power is obtained from the battery and battery remains floating and the regular load is drawn from the mains and battery remains fully charged and when the main supply fails the energy for load circuit is drawn from the battery. The back up time will depend on the capacity of the battery ( Ampere Hour ) (The circuit details are elaborate and drawings, design and component values can b collected from any design book.)

There can be UPS with Diesel Generators with stand by in-house generating system with auto change over circuit and breakers in the bus bar panel for large Industrial units and software development / Service organisations.

Inverter is only a stand by power unit which can be manually or automatically switched on when the main fails. It will consist of Battery inverter and change over switch. The inverter theoretically does the opposite function of rectifier function. that is converting DC to AC

here are some simple schematics of an Inverter and a UPS

Hi Manish

Inverter is the most important part of a UPS. UPS which stand for Uninterrupted power supply comprises rectifier, battery, inverter and contactors or static switches. The rectifier supplies the inverter and also charges the battery. During power failure the battery supplies the inverter which then supplies the load. When power is restored, the load is switched back to main supply.

The best way to find out, is to build your own!

http://icrontic.com/articles/super_ups

http://www.dansdata.com/diyups.htm

To my mind, there are basically two different types of UPS. One where the mains if interrupted, is switched over to a battery driven inverter (or DG set) and the ones where basically the mains supplies a battery charger, which charges a battery which then has an inverter running full time supplying the load at mains voltage.

The difference being that there should never be an interruption in the supply with the second type, important for PCs and the like, which don`t like "switch over spikes" and actually simpler to build I feel.....Also the second type, if the mains comes back, just picks up again with charging the battery.....

The problems with the first type means that for many usages it is just not good enough....as you probably have to accept a power loss for a short time at least. Then there is the problem of "when to go back" to using the mains when it returns - is it now stable or not?

For large loads like buildings, the first type of UPS is the only one possible I would imagine, with a large DG set or similar!!!

As to whether it is actually possible to have a DG set, running at a low loading but online and in parallel with the mains, to instantly pick up on a large load I could not personally say, but it should be theoretically possible I feel......

For computers and other application where hamonics matters we go for UPS while for home application like lamps, fans, cooler etc we go for inverter with battery backup.

In normal operation when AC power is available inverter is bypassed and mains (1) chargers the battery (2) feed the load.

In case of failure of normal power supply inveter comes into the picture and feed the load throgh the battery. We can say inverter is a Offline UPS with automatic/Maual switching.

My questionis what is the principle difference in these two.

Can you provide me the circuitery for both UPS and Inverter with battery back up for my reference.

No, I am not a supplier of schematics.....I do my own thing and make my own mistakes.

Thanks

Regards

Manish

More specifically, off-line (backup battery power kick-in via inverter at mains failure) UPS is generally adequate for most computer powering provided:

• UPS design response time is exceptionally good and
• UPS output is full sine wave

However, in instances (e.g., processing intensive such as servers, or critical applications such as medical or surgery theatre) where even microsecond transition times could be problematic, on-line UPS (power output from battery and inverter at all times) is preferred, to ensure zero-transition-time interruption of power to computer or other power networked equipment.

Good post, you would never have me with a computer or other sensitive equipment on one of those "transitional" Units, there is always a glitch no matter how good.....and if I need my computer ready all the time, the On-Line UPS is the better, and to my mind slightly cheaper option with less chance of a failure.....that you can also build yourself fairly easily!

Andy,

Thare also is another type of ups. The Flywheel ups. Allthough those are sometimes considered mere power conditioners rather than an ups, but still worth mentioning.

As the name suggests they are basically a motor-gen set with a large inertial value, so the generator keeps spinning for a bit after the drive motor loses power.

There are many variations of the what is known as rotary UPS where a generator is normally driven by a induction motor drawing its power from the mains .A fly wheel attached to the system keeps the generator spinning for a few seconds when the diesel engine comes on and gets coupled through a centrifugal clutch or by a similar means.The sizing of fly wheel is of utmost importance.The other version uses a DC motor driving a generator drawing its power from mains through a controller and with battery back.This is little messy but preferred in some cases.Rotary ups is used in Reactor coolant pumps in Nuclear power plant where no interruption is permissible.I have also seen small rotary UPS with some cnc machines where DC motor was used to hold the speed accurately so that the frequency was maintained at desired value .Now we have rotary UPS with inverter back up.The induction motor normally draws power from the mains but when supply fails the battery powers it through inverter till engine comes on.These are more with smaller sets where battery need not be large.

Rotary, not flywheel, that's what I meant to say. I was thinking of the principle and misqouted the name.

Thanks for the correction Guest.