What are the specifications of the transformer capacity?
Select the transformer capacity, to the existing load as the basis, appropriate consideration of load development, select the transformer capacity can be determined in accordance with the 5-year power development plan.
When 5 years of power development is clear, little change and then the load is not less than 30% of the transformer capacity:
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?SN = KS ΣPH / (cosφ η)
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?Where: SN - box change in 5 years required configuration capacity, kVA
ΣPH - 5 years old with financial calculations, kW
KS - at the same time, generally 0.7 to 0.8
Cosφ - power factor, generally 0.8 ~ 0.85
Η - transformer efficiency, generally 0.8 ~ 0.9
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?According to the formula generally KS = 0.75, cosφ = 0.8, η = 0.8
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?SN = 0.75ΣPH / (0.8 × 0.8) = 1.17ΣPH
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?Example: a district in accordance with 50W / m2 design, then
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?PH = 50 × 19200 = 960kW
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?SN = 1.17 x 960 = 1123 kW
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?So the district selected three 400kVA transformer.
The optimum load rate of the transformer (ie, the load rate at the highest efficiency) is not in the rated state, but between 40% and 70%. The load factor is too high and the loss increases obviously. On the other hand, Margin is small, a slight increase in load, you need to replace the large capacity box change, frequent capacity is bound to increase investment, affecting power supply.
The choice of transformer capacity has a great impact on the comprehensive investment efficiency. Transformer capacity selected too large, there "big horse car" phenomenon, not only a one-time investment, no-load loss is also large. Transformer capacity selected too small, transformer load loss increases, economically unreasonable, technically not feasible.
