Transformer

Use more than 400KW for better Transformer life..as standard transformer available in market.

Since we don't know where you live it is impossible to give a meaningful answer.

Try giving more information.

The real answer is your local electrical code.

Please consider building expansion near future, say at 5 or 10 years estimated total load. In this you wont have to replace another transformer.

considering your load p.f to be o.8 (which is a practical value for residential single phase loads ), your apparent load will be : 400 /0.8 = 500KVA , so a transformer with 500KVA rating will be perfect for your present load. however you should buy a transformer with 20% extra capacity of 500KVA to account for any extra future load. so that means a transformer with capacity : 1.2 x 500 = 600 KVA . so buy a transformer of 600KVA rating.

You need to perform an analysis of the instrument loads (starting current, operating current under load, etc) as well as an analysis of operating duty cycles (which equipment will be on when, etc).

If you cannot do this then get someone qualified to do it, no one here can possibly guess without a great deal more information, and even then.......

Is this a homework question?

If this is a 1Φ load at 400kW, I'd consider switching to 3Φ. After 100kW it's <em>ALOT</> more efficient.

But as others have posted, we need more information here.

Hi!

My friend u r right but can u tell me the calculating formula ?

If my loads are of one distribution is of 89kw, second of 150 ,third of 161kw.

Now can u tell me my transformer's rating.

Rather than trying to calculate,fix a power analyser or data logger for at least 8hrs and record V,I,Hz, Var, W, pf, THD, max demand instantanous values of I,V etc and select the transformer size making allowance for future load.

Hi Hitesh, if you know the KW Load, I have to presume that you also know your full load current, you will also know what your possible load changes are going to be in the next 10 years.

I hope your load is spread over 3 phase and by knowing the supply current per phase you can work out what you need for your existing supply and also plan what you would need for expansion over the next 5-10 years.

I hope this is of help

Cheers

Joe

The other suggestion (Just Joking) consult your local clairvoyant.

Hi Joe,

your right but this is for my upcoming project and yet all instruments are not installed so that i don't know the current inspite of that wanna know the transformer rating to demand transformer from electrical co. cause it takes to long time in process.

I am already running with calculating 20% extra load.

This is my Hospitality project.

I can calculate app. current cause my approximate division of circuits are 1st of 89kw

2nd of 150kw & 3rd of 161kw.

Now can u tell me the calculating formula for this.

Regard,

Hitesh

If you have 3 circuits as described, and want to use a 3 phase supply transformer, then the transformer size will still be 400 kW.( Single phase or 3 phase).

89+150+161= 400 kW

The only thing that changes is the distribution panels ...

The transformer will ve in KVA and not KW.

OP had to tell the type of load (and the expected pf) even if we assume it to be about 0.8 it becomes 500KVA but then the loads (which may give the abnormal starting current requirements) , diversity factor etc would be needed for the sizing.

Since the P.F. is not mentioned, and it seems that the load is made of INSTRUMENTS, the mentioning of kW will definitely trigger the question: what type of load etc, from the supplier so that he could specify the kVA.

In any case, I mentioned a p.f. of 0.8 and gave the kW rating for it. My answer is perfectly correct. The kVA can be deducted by removing the 0.8 from the formula. Specifying kW at o.8 p.f. is complete. (0.8 is standard p.f. for any power supplier)