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Mathcad - 05-15

Mathcad - 05-15 - kVA β‰ kW kVAR β‰ kW Srated:= 75β‹… kVA...

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Unformatted text preview: kVA ≑ kW kVAR ≑ kW Srated := 75β‹… kVA Problem 5-15: Vprated := 208β‹… V Vsrated := 480β‹… volt Rp := 0.0132β‹… Ω Xp := 0.0189β‹… Ω Rfels := 101.5β‹… Ω Rs := 0.07β‹… Ω Xs := 0.10β‹… Ω Xmls := 37.15β‹… Ω Fp := 1.0 Solution First find the turns ratio a := Vprated Vsrated a = 0.433 The equivalent winding impedance referred to the high side (secondary) is: Rp + jβ‹… Xp + ( Rs + jβ‹… Xs) 2 a Zeqs := Zeqs = 0.14 + 0.201j Ω ΞΈ := acos ( Fp ) ΞΈ = 0 deg The transformer delivers rated voltage so: angle is zero since unity Fp Vfl := Vsrated Vfl = 480 V At full load, the current is: Is := Srated j β‹… ΞΈ β‹…e Vfl Is = 156.25 A The primary voltage, referred to the secondary side at full load, is calculated by adding the drop across the equivalent impedance (caused by the load current) to the secondary full load voltage Vreferredp := Vfl + Isβ‹… Zeqs Vreferredp = 501.921 + 31.352j V Vreferredp = 502.899 V which is the no load voltage Vnl := Vreferredp VR := Vnl βˆ’ Vfl Vfl VR = 4.771 % ...
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