Transformer Loss Estimation

The residential societies which take single point supply from SEB, find significant losses in their electricity accounting. More often than not, these losses are combined with the common area consumption and are accounted for. One contributor to these losses is the Transformer Loss.

The societies use transformer to step down the voltage – say from 11 KV to 433 V. There are certain losses at the transformers. It is useful for the societies to estimate these losses on the regular basis and ensure that no untoward thing is happening.

Technically, the transformer losses are categorized as Iron Losses and Copper losses. The iron losses are load independent and the copper losses are load dependent losses.  The transformer manufacturers or test certificates do provide some information for these losses.

The most accurate way to calculate the transformer losses is to contact the manufacturer and get the loss calculation or the loss curve for the losses. There are however simpler ways to estimate the transformer losses.

Either the manufacturer’s certificate or test report may have information with respect to Losses at no load and losses at Load (or full load). One may consider the losses at full load as fixed losses and the difference of load losses and no load losses as a linear variable loss.

Let us take an actual case: the transformer (11 KVA) certificate says as follows:

No Load Losses:                                1320 W

Load Losses:                       10496.63 W at 52.487 A

The calculated losses would be:

Monthly energy (kWh)


Average Load (kW)


Average Current (A)


Average Loss (kW)


Total Loss (kWh)


% Loss



One should be able to take into account these loss calculations in an overall loss calculation picture and determine the health of the transformer and the distribution network.

For further information or assistance, please reach out to us at This email address is being protected from spambots. You need JavaScript enabled to view it. .


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