Dear Fujiatma P Napitupulu

The distribution transformer when lightly loaded is still having the same iron losses ( i.e. a combination of hysterisis and eddy current loss) which is also called as the constant loss, so long as it is supplied with constant primary voltage which is true for distribution transformers. Hence the energy loss percentage is high, though the variable losses (copper loss) may be low. That is the reason why all day losses, as these losses are called is an important specufication for distribution transformers.

Hope my answer satisfies your question.

Regards,

Sudha

Thank you Sudha Balagopalan

and i want to ask one more question,

Do You have a research/journals about under load transformer ( transformer when lightly loaded)? or had read the journal about it ?

if you had, would you please share it for me.

Thank You

Efficiency would be maximum when iron loss equal to cooper loss, for any transformer. Hence from cooper loss, loading for maximum efficiency could be obtained for constant power factor and voltage as iron loss is constant and known. Though with lower load, due to consta magnetizing current the low power factor would need more capacitive loadin to improved power factor, or system efficiency would reduced considerably. Refer my papers on, online transformers overload time limits computation and control....

a transformer has two loss parts : Noload Loss and Load Loss.

The first part, No load loss, is constant and when transformer is energized, It will be in account.

The second part, load loss, depend to load percentage and this part will more when transformer load is more.

As transformer efficiency is equal to (load)/(load + noloadloss + loadloss), when transformer load is small, efficiency is lower.

Best

Mahdi

I agree with Prof. Bupendra Desai. Efficiency is maximum when iron losses equal copper losses. As explained by Prof. Sudha Balagopalan at light loads copper losses may not be predominant, whereas under high load conditions they have a predominant role.

As you have yourself indicated energy losses in terms of percentage will be high at light loads.

Transformer is highest efficiency machine in electrical equipment.Under load There are two types of losses one is known is magnetic loss or iron loss which is considered to be constant at any percentage of load. Other loss is copper loss also known as current dependent loss (I square R loss).On no load there is only a magnetic loss (Iron Loss). So as we have in question the copper loss is current dependent loss so this loss changes with change in load current.

Transformer has its maximum efficiency when copper loss and iron losses become equals. so we can say copper losses are variable losses because current varies as a function of time. For transformer we take all day efficiency.

Regards

PE.Tech. Sultan Mahmood Yasir

Gujrat, Pakistan.

I do agree with Prof. Bupendra and Rajagopalan Raghavan.

I do agree with prof Rajagopalan Raghavan.