Mathcad - 05-14

Mathcad - 05-14 - kVA ≡ kW kVAR ≡ kW Srated := 75⋅...

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Unformatted text preview: kVA ≡ kW kVAR ≡ kW Srated := 75⋅ kVA Problem 5-14: Vprated := 208⋅ V Vsrated := 480⋅ volt Rp := 0.0132⋅ Ω Xp := 0.0189⋅ Ω Rfels := 101.5⋅ Ω Rs := 0.07⋅ Ω Xs := 0.10⋅ Ω Xmls := 37.15⋅ Ω Fp := 0.8 leading Solution First find the turns ratio a := Vprated Vsrated a = 0.433 The equivalent winding impedance referred to the high side (secondary) is: Rp + j⋅ Xp + ( Rs + j⋅ Xs) 2 a Zeqs := Zeqs = 0.14 + 0.201j Ω θ := acos ( Fp ) θ = 36.87 deg The transformer delivers rated voltage so: angle is positive since leading Vfl := Vsrated Vfl = 480 V At full load, the current is: Is := Srated j ⋅ θ ⋅e Vfl Is = 125 + 93.75j 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 + Is⋅ Zeqs Vreferredp = 478.726 + 38.234j V Vreferredp = 480.25 V which is the no load voltage Vnl := Vreferredp VR := Vnl − Vfl Vfl VR = 0.052 % ...
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