Mathcad - 11-09

Mathcad - 11-09 - Problem 11-9: Prated := 10⋅ hp Vt :=...

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Unformatted text preview: Problem 11-9: Prated := 10⋅ hp Vt := 125⋅ volt Irated := 75⋅ amp Rfldckt := 125⋅ Ω Ra := 0.1⋅ Ω n rated := 1750⋅ rev min At no load, the armature current is zero so Ea = Vt At full load, the armature current is the line current minus the field current If := Vt If = 1 A Rfldckt Ia := Irated − If Ia = 74 A Ea := Vt − Ia⋅ Ra so the CEMF is Ea = 117.6 V The flux is virtually constant for the shunt DC motor, so the CEMF is proportional to speed n fl := 1750⋅ n nl := SR := Vt Ea rev min ⋅ n rated n nl − n fl n fl Pout := 10⋅ hp 100% 3 rev n nl = 1.86 × 10 min SR = 6.293 % Pin := Vt ⋅ Irated Pout = 7.457 kW η := Pout Pin 100% η = 79.541 % Pin = 9.375 kW ...
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