Most common connections are Y-Δ, Δ-Y, Δ-Δ and Y-Y star-star is common in EHV and HV, although it presents imbalance and 3rd harmonic problems, being necessary the third winding above referred. Also Read: Transformer Efficiency, All day Efficiency & Condition for Maximum Efficiency.Table 1 shows the most common vector groups. When neutral point is accessible letter “ N” or “ n” is added to the symbol. Total losses ( P t) are given by the equation:
It is common that transformers that are not in service permanently (example: public lighting transformers) are required to have reduced iron losses.Īlso Read: Maintenance of Transformer – Power Transformers Maintenance, Diagnostic & Monitoring The iron losses, are the sum of hysteresis losses and eddy current losses, which happens even when the transformer has no load (due to this fact iron losses are also known as no-load losses).īoth resistive losses and iron losses are indicated by the transformer’s manufacturer. The resistive losses, due to Joule effect on the windings, depends on the current that goes through the turns of the windings, which results from the loads connected to the transformer. Transformers are subject to two types of losses: The rated frequencies are usually 50 Hz and 60 Hz. Considering a transformer with N 1 turns in the primary winding, N 2 turns in the secondary winding, V 1 and V 2 the primary and the secondary voltages, and I 1 and I 2 the primary and the secondary currents, the ratio can expressed by the following equation:
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