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#1

# The ratio of magnetizing current of a transformer against of full load current of transformer

please shear what is the ratio of magnetizing current of a transformer against of full load current of transformer.
09-01-2014 12:56 PM
Top #2
Ghulam,

Your question requires clarification. In what context are you interested; initial energization, no load loss, leakage current, etc.

Alan
09-01-2014 03:27 PM
Top #3
The magnetic inrush current is normally 12X the full load current at 0.1 sec and 25X at 0.01 sec. This is used in fuse co-ordination studies.
09-01-2014 06:07 PM
Top #4
Steady state magnetizing current of a transformer is always less than 2% of its full load nominal current at its rated voltage and frequency.and at nominal tap position of Off Circuit Tap Switch ( OCTS) or On Load Tap Changer (OLTC) as the case may be.
For ratings less than 500 kVA it can be as high as 2.5 % .
09-01-2014 08:35 PM
Top #5
It depends on the size and type of transformer. No-load magnetising current as % of full load current with today's technology is as below:
Distribution Transformers :
Stacked core – 3% of Full Load current
Wound core – 2 % of FL current (Actual values: 0.5-1.5 % with ZDKH –M4 material at 1.7 T, Power Factor -0.8-0.9)
Power Transformers:
20-315 MVA -0.1 % ( 20 MVA) to 0.05 % (315 MVA), Power factor -0.5-0.9
500 MVA single phase 765/400 kV Auto-Transformer – Current=0.03 % PF=0.41