NO-LOAD LOSS IN POWER TRANSFORMER

NO-LOAD LOSS IN POWER TRANSFORMER

NO LOAD LOSS is the other type of transformer loss which is also known as CORE LOSS. Core loss exists for the reason that transformers of any kind requires electrical currents and magnetic fields that is needed to magnetize the core of the transformer, the sad part is that they are present whenever the transformer is energized whether loaded or unloaded. Unlike the winding loss, core loss requires a constant value regardless of the transformer load; in short, core loss does not vary as transformer load changes. For example, if a power transformer has a core loss of 24kW, 24kW of power must be drawn from the source of supply to cover these losses at all times when the transformer is energized, even if the transformer load side are open.

Furthermore, the analysis of No-Load loss/core loss can still be broken down to parts. Core losses mainly consist of Eddy current loss and Hysteresis Loss of which both are the magnetic properties of the transformer core. In actual practice in substation design, eddy current and hysteresis losses are no longer considered since the project engineer‘s only concern by then is the final value of the no-load loss rating but for the sake of discussion, we will further touch the nature of these losses.

We have discussed in the previous TRANSFORMER LOSS FORMULA articles how eddy current and hysteresis are computed but we were really not able to tackle the principles behind how this phenomenon even exists.

To start with, EDDY CURRENT LOSS is an energy loss associated with the undesirable currents (eddy currents) that exists in the conducting core material due to an induced voltage caused by a fluctuating magnetic field. This is a result that is present every time the primary of an iron-core transformer is energized by an AC source. These currents that are caused by induced voltage will flow to the transformer core which dissipates power in the form of heat.

HYSTERESIS LOSS on the other hand, is also power dissipation in the form of heat. The nature of this loss is caused primarily by the effect of frequency of alternating current to the transformer core. Every time magnetic field is passed through the transformer core, the core material tends to be magnetized. In order for it to be magnetized, the domains in the core must align themselves with the external field produced. Due to the alternating nature of the current, as a result, the field direction also reverses which makes the domain’s pole turn for it to be aligned again to the new direction of the field. With the case of a 60Hz rated substation transformer, the said tiny domains must realign to the external field twice during each cycle or since 60Hz is equal to 1 cycle, will yield a total of 120 times of realignment. That is why, in order for transformer manufacturer to minimize this hysteresis loss, proper choice of core material is necessary.
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CONTINUE TO TRANSFORMER LOAD LOSS