xfmr question?
- Thread starter steveng
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So simple !
If you search in this forum, u may get more.
The formula is here ,
single phase current = Tranformer capacity in VA / 1.732*208
Now u can calculate...
For loading of this transformer you can consider 180 VA per receptacle and for computer also you can consider around 200 VA as load.....
You can calculate now
If you search in this forum, u may get more.
The formula is here ,
single phase current = Tranformer capacity in VA / 1.732*208
Now u can calculate...
For loading of this transformer you can consider 180 VA per receptacle and for computer also you can consider around 200 VA as load.....
You can calculate now
Easy way:
Easy way:
I find it confusing to compute the "sum" of the line currents which strictly speaking add to zero. I prefer to compute the current of one leg, to wit:
Each leg of the wye can deliver 10KVA. Then the max current per leg is,
Imax = 10KVA/120V = 83A (line current)
This is true irrespective of the load configuration.
No need to worry about 208V and 1.73.
Easy way:
I find it confusing to compute the "sum" of the line currents which strictly speaking add to zero. I prefer to compute the current of one leg, to wit:
Each leg of the wye can deliver 10KVA. Then the max current per leg is,
Imax = 10KVA/120V = 83A (line current)
This is true irrespective of the load configuration.
No need to worry about 208V and 1.73.
I know that!
I know that!
I understand that perfectly, but there is no place one can measure three times the line current in the system, therefore I prefer to think in terms of individual line currents.
A similar discussion arose not long ago where an interim result yielded 831V in a 480V system although the final calculation was correct.
Now, it is is perfectly alright to add power, real or apparent, in this way.
I know that!
kalanjeya said:
I understand that perfectly, but there is no place one can measure three times the line current in the system, therefore I prefer to think in terms of individual line currents.
A similar discussion arose not long ago where an interim result yielded 831V in a 480V system although the final calculation was correct.
Now, it is is perfectly alright to add power, real or apparent, in this way.
- Location
- Illinois
- Occupation
- retired electrician
Steve,
Don
That is not correct. It should be 30,000/ (208 * 1.73) and then the answer is 83.37 amps. You are doing (30,000/208) * 1.73.
Don
Steve...hang onto that link I put up last night:
[Useful Formulas]
Here's another one:
[Electrician Calculators]
[Useful Formulas]
Here's another one:
[Electrician Calculators]
Not that there is anything wrong with that method, I prefer to calculate available line current on a 208Y/120 system as:don_resqcapt19 said:
30,000VA ? (120V ? 3) = 83.33...A (i.e. 83 1/3 Amperes)
This stems only from the fact that the 208 voltage is rounded, whereas the 120 voltage is not...120V ? √3 = 207.846V
However, on a 480Y/277 system, the 277 voltage is the one that is rounded...
(480V ? √3 = 277.128V)
...so I calculate available line current as, for example:30,000VA ? (480V ? √3) = 36.084A
The one constant through all my calculations, if I'm doing it on a scientific calculator, is that I always use √3 opposed to 1.73 or 1.732. The number of keys pressed is usually the same or less.
Smart $ said:
That's the beauty of math:
As long as you have correct formula or correct variation of the formula, the answer will be the same.
Here is little chart from the [Useful Formulas] link;
[FONT=Arial, Helvetica]For 208 volts x 1.732, use 360[/FONT]
[FONT=Arial, Helvetica] For 230 volts x 1.732, use 398[/FONT]
[FONT=Arial, Helvetica] For 240 volts x 1.732, use 416[/FONT]
[FONT=Arial, Helvetica] For 440 volts x 1.732, use 762[/FONT]
[FONT=Arial, Helvetica] For 460 volts x 1.732, use 797[/FONT]
[FONT=Arial, Helvetica] For 480 Volts x 1.732, use 831
[/FONT]
[FONT=Arial, Helvetica] For 230 volts x 1.732, use 398[/FONT]
[FONT=Arial, Helvetica] For 240 volts x 1.732, use 416[/FONT]
[FONT=Arial, Helvetica] For 440 volts x 1.732, use 762[/FONT]
[FONT=Arial, Helvetica] For 460 volts x 1.732, use 797[/FONT]
[FONT=Arial, Helvetica] For 480 Volts x 1.732, use 831
[/FONT]
Much simpler and less keys to press 
hardworkingstiff
Senior Member
- Location
- Wilmington, NC
rattus said:
Rattus, there you go getting practical,
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