Page 273 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

• W1 read only the core loss

• W2 read the copper loss only at the current set from T.
• W1 +W2 is twice the loss of a single transformer
• Power taken from source is only W1 +W2
• Continuous losses create heat in transformer
• Temperature rise characteristics data can be found out by using thermocouples
• No full loading is needed to get temperature rise data.
Core loss is practically constant in all load conditions

Full load copper loss = X watts
1 1 X
load copper loss = ( ) . X watts =
2
2 2 4
1 1 X
load copper loss = ( )2.X watts =
4 4 16
kW = kVA cos f
Condition for maximum efficiency

• Cu loss = Iron loss
• Given iron and full load cu loss,
• Then the load at which two losses would be equal (i.e. corresponding to maximum efficiency)
Iron loss
= Full load x
√ Full load copper loss
Efficiencies of transformer

• Ordinary efficiency
Output in watts
Ordinary efficiency =
Input in watts
• All day efficiency
Output in kilo - watts hours
All day efficiency = (24 hours)
Input in kilo - watts hours
• Ordinary efficiency > All day efficiency

Transformer equivalent circuit
Transformer circuit (Fig 19)

Fig 19

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CITS : Power - Electrician & Wireman - Lesson 41-49