Sizing of Transformer for Single Phase and Three Phase loads

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nanjangud

Member
Currently I am executing a project wherein power supply is to be provided to 5 nos. of Analyzer cabinets. The power supply to these analyzer units are at voltage levels 120V and 220V. The kVA of the load connected to each analyzer cabinet is - @120V, 1Phase, 60Hz = 2320kVA and @220V, 1Phase, 60Hz = 13140kVA.
Please tell me how to carry out the transformer sizing and specify the voltage ratio for this application.
 
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ndc81167

Member
transformer sizing

transformer sizing

iam trying to feed a welder that draws 65a@460 and all i have available
is a 100a 208v source,, is there a xfrmr that can get me 208 to 460?
and would the 100a 208v source be adequate?
 
Besoeker

Besoeker

Senior Member
Location
UK
ndc81167 said:
iam trying to feed a welder that draws 65a@460 and all i have available
is a 100a 208v source,, is there a xfrmr that can get me 208 to 460?
and would the 100a 208v source be adequate?
Click to expand...
Yes, you can transform from any voltage to any other.
No, your source is not adequate for continuous operation.
 
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nakulak

Senior Member
you are designing a petrochemical plant or a power plant ? (you don't have an existing power grid ?)
 
ohmhead

ohmhead

Senior Member
Location
ORLANDO FLA
ndc81167 said:
does anyone know how to calculate the porper primary source required?
Click to expand...

Well what the other posts are trying to say is you need to read article 630 .

The transformer would be a step up for your welder but at 65 amps the kw = around 54kw that means your primary 208 volts would be higher than 100amps so thats not going to work i think around 150 amps but thats at 100 percent of your load .

I would go to a larger transformer 75 kva but iam not a engineer this is for 3 phase .

But is the welder 3 phase ? what type ? how is it to be used duty cycle ?
 
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bob

bob

Senior Member
Location
Alabama
nakulak said:
you are designing a petrochemical plant or a power plant ? (you don't have an existing power grid ?)
Click to expand...

This is a different guy. He sneaked into this post and started asking his own questions. That's not the way its done. ndc81167 you should start your own post.

ndc81167
You are listed as an EC and you can not do these calculations? I smell a skunk.
 
LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
I hate to contribute to a thread derailment, but . . .
ndc81167 said:
iam trying to feed a welder that draws 65a@460 and all i have available
is a 100a 208v source,, is there a xfrmr that can get me 208 to 460?
and would the 100a 208v source be adequate?
Click to expand...
When you boost a voltage, the lower-voltage primary must be able to deliver the greater lower-voltage current. Remember: power = volts x amps.

The current ratio is basically the inverse of the voltage ratio. If you need 65a at 460v, you'll need (460/208 * 65, or 460*65 / 208) 143.75a at 208v.

In other words, at slightly less than half the voltage, you'll need slightly more than twice the current to deliver the same amount of power.



Added: Mod Squad, please relocate as deemed necessary.
 
ohmhead

ohmhead

Senior Member
Location
ORLANDO FLA
nanjangud said:
Currently I am executing a project wherein power supply is to be provided to 5 nos. of Analyzer cabinets. The power supply to these analyzer units are at voltage levels 120V and 220V. The kVA of the load connected to each analyzer cabinet is - @120V, 1Phase, 60Hz = 2320kVA and @220V, 1Phase, 60Hz = 13140kVA.
Please tell me how to carry out the transformer sizing and specify the voltage ratio for this application.
Click to expand...


Well whats the real kva of the analyzers ?
 
LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
nanjangud said:
Currently I am executing a project wherein power supply is to be provided to 5 nos. of Analyzer cabinets. The power supply to these analyzer units are at voltage levels 120V and 220V. The kVA of the load connected to each analyzer cabinet is - @120V, 1Phase, 60Hz = 2320kVA and @220V, 1Phase, 60Hz = 13140kVA.
Please tell me how to carry out the transformer sizing and specify the voltage ratio for this application.
Click to expand...
Presuming the kva's are really va's, you just add them up: 5 * 2320 + 5 * 13140 = 77,300 va.

However, since you don't have six loads, you can't simply divide by 3, so you're looking at around a 90kva supply.

If we're wrong about your kva's being va's, make that around 90MW.
 
chaterpilar

chaterpilar

Senior Member
Location
Saudi Arabia
Some more data is required..

What is the available 3 phase voltage from the board?

your load is 15460 va = 15.46 kva

let us say your incomer is 380 volts three phase then you need a 10 kva 380volts 3phase to 220 volts 3phase step down transformer (with star secondary).

Be careful to balance the load equally on each phase and use the neutral to phase for 120 volt loads.

cheers.
 
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