Choice of transformer rating: Difference between revisions

From Electrical Installation Guide
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where
where
*Pa = kVA rating of the transformer
*U = phase-to-phase voltage at no-load in volts (237 V or 410 V)
*In is in amperes.


For a single-phase transformer:  
{{def
|Pa|kVA rating of the transformer
|U|phase-to-phase voltage at no-load in volts (237 V or 410 V)}}
<br>'''In''' is in amperes.
 
For a single-phase transformer:


<math>\mbox{In}=\frac{\mbox{Pa}\times10^3}{\mbox{V} }</math>  
<math>\mbox{In}=\frac{\mbox{Pa}\times10^3}{\mbox{V} }</math>  
Line 91: Line 93:
where  
where  


*V = voltage between LV terminals at no-load (in volts)
{{def|V|voltage between LV terminals at no-load (in volts)}}


Simplified equation for 400 V (3-phase load)  
Simplified equation for 400 V (3-phase load):
*In = kVA x 1.4


*In = kVA x 1.4
The IEC standard for power transformers is IEC 60076.
*The IEC standard for power transformers is IEC 60076.


[[ru:Выбор номинальной мощности трансформатора]]
[[ru:Выбор номинальной мощности трансформатора]]
[[zh:变压器额定容量的选择]]
[[zh:变压器额定容量的选择]]

Revision as of 18:09, 16 November 2016


When an installation is to be supplied directly from a MV/LV transformer and the maximum apparent-power loading of the installation has been determined, a suitable rating for the transformer can be decided, taking into account the following considerations (see Fig. A15):

  • The possibility of improving the power factor of the installation (see Power Factor Correction)
  • Anticipated extensions to the installation
  • Installation constraints (e.g. temperature)
  • Standard transformer ratings

Apparent power kVA

In (A)
237 V 410 V
100 244 141
160 390 225
250 609 352
315 767 444
400 974 563
500 1218 704
630 1535 887
800 1939 1127
1000 2436 1408
1250 3045 1760
1600 3898 2253
2000 4872 2816
2500 6090 3520
3150 7673 4436
Fig. A15 – Standard apparent powers for MV/LV transformers and related nominal output currents

The nominal full-load current In on the LV side of a 3-phase transformer is given by:

[math]\displaystyle{ \mbox{In}=\frac{\mbox{Pa}\times10^3}{\mbox{U}\sqrt3} }[/math]

where

Pa = kVA rating of the transformer
U = phase-to-phase voltage at no-load in volts (237 V or 410 V)
In is in amperes.

For a single-phase transformer:

[math]\displaystyle{ \mbox{In}=\frac{\mbox{Pa}\times10^3}{\mbox{V} } }[/math]

where

V = voltage between LV terminals at no-load (in volts)

Simplified equation for 400 V (3-phase load):

  • In = kVA x 1.4

The IEC standard for power transformers is IEC 60076.

ru:Выбор номинальной мощности трансформатора zh:变压器额定容量的选择

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