3 Phase to Single Phase Voltage Conversion in Stabilizer

The 400V will reduce the line losses between the UPS to the feeder point. Except that I don't see any advantage, since you have already 110V supply available with you (and I assume thet you don't have the 400V supply available?)

If it is available too then does it really matter ?

Another aspect is the feeder lines (or transformer) capacity to take the load demanded by this UPS.

And lastly, it was you who has asked for this specification (400V/110V step down)

Pakistan uses (I believe) a 230V single phase, 400V three phase supply (50Hz). A conversion is necessary if you want single phase 110V (to power American-made equipment perhaps?).

As for the three phase supply, what is the power or VA rating of the UPS? Large UPS are designed to operate off a three phase supply to handle the high current (and it sounds like your UPS is powering more than just a computer or server room).

Additionally a "stabilizer" in this case could be being used as an additional supply power quality filter for the UPS (to further protect the UPS).

i guess thats the reason of using the 3 phase supply, since the UPS is feeding other field systems too, rather than just supplying power to the DCS.

Thanx everyone for the help!

Regards.

Your question needs more details.

1. Have you read the manual for full specs like:

a. Input Voltage - you say 110V ?

b. Output Power

Please clarify:

<<< There's a 3 phase 400 V incoming power to the UPS which is then converted to 110V AC single phase to be utilized by the process plant. >>>

Is the power to your PLANT is 110V or to UPS alone or all the premisis is running on 110V ?

I think there are some H-Ups everywhere who do such facinated jobs in under-developed countries:

On foreign tours buy Equipment from USA 110V, 60 Hz, return home order for a Step-down Transformer without knowning that the system in Equip really needs 60Hz not 50Hz due to internal clock & motors needs 60 Hz.

Or the UPS & ThePlant is a free Gift from a donor country?

Any further details may help to HELP.

Have a fine day.

After reading all of the posts so far, my guess is that the 110 volt supply you have may be 50HZ and the output from the UPS may be 60HZ. Check your frequency from each source if possible to determine if they are different. Otherwise, 110 volt supplied to an appropriate UPS should be sufficient except that the current draw will be substantially higher (amperage). This may be the primary reason for supplying 400 volt instead of 110 volt to the input of the UPS.

The sole purpose of a Uninterpretable Power Supply is to provide power during power failures. Monitor your power line and you will be surprised at what you learn about power failures. Most power failures are not a full loss of voltage. There are many different types of power failures:

One phase dipping voltage; Two phases dipping voltage; Three phases dipping voltage; One phase going to zero; Two phases going to zero; Three phases going to zero; One phase going to zero and two phases going to 50%: and any combination of theses events and more for varying periods of time.

So, a UPS fed from three phase power has a good chance that it can continue to provide single phase power indefinitely under certain power line failures without even drawing power from its battery bank.

Even better is to feed a critical system from two different three phase power generating stations. (I've worked on these rare facilities which are fed from multiple sub stations.)

Typically a UPS coverts AC to DC then back to AC. The AC to DC conversion is typically done with a phase controlled rectifier. In order to maintain a constant DC level, the amount of time within a half cycle that the rectifier is turned on is proportional to the AC input voltage. If the input voltage dips, the phase control rectifier turns on longer. I've worked on systems that output 230vac in which we first stepped up the input voltage to 800vac using a transformer before the phase controlled rectifier. This was necessary because the utility power was of very poor quality and our equipment had to be able to provide full output power under varying power dip failures.

Dear Afifa;

It is totally depend upon the user requirement that user have three phase or single phase supply, when your specification mentioned that we require three phase connection then vendor use scott tranformer which is a type of circuit used to derive two-phase (2-φ) current from a three-phase (3-φ) source or vice-versa.

Any UPS requires Battery backup; hence charging. If it is On-line UPS the AC to DC power rating should be so high that it should be able to give power to load as well as battery charging. If your UPS rating is very high it will unbalance if you use single phase. Hence to balance in-put mains power 3 phase is used. In my plant all that UPS above 3KVA we prefer 3 phase in put.

I ve tried to figure out what u called a UPS with a 3 phase supply and an out put of 110. I dont think that should be the proper definition a UPS. What U have is a power supply (AC-DC-AC). The power supply / Inverters Drives is better and more reliable in its quality of supply and equipment protection. Other faults that are prone in normal mains supply are taking care of in the power supplies. A 110 derived from 3-phase 400V is much more reliable, realistic and well regulated.

Dickson

Dear Poster.

It seems not to be fair to post a question and not to follow it.