patel cheat sheet

# patel cheat sheet - Magnetic Circuits φ = N*I(L/μ*A =...

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Unformatted text preview: Magnetic Circuits φ = N*I / (L/μ*A) = m.m.f / R (wb) φ = m.m.f / R same as I = E/ R N*I = m.m.f = (a*t) turns R = L/(μ*A) = reluctance (resistance) of flux path (H) Ratio μ = μ o / μ r μ o permeability air= 1.2566*10^-6 (H/m) B = φ / A flux density (Wb/m 2 ) H = N*I /L magnetizing force intensity (a*t/m) P h = K h *f*B m n watts K h = proportional constant n= steinmetz constant 1.4 to 1.8 Electrical Machines E rms =4.444*f*N*Φ(rms voltage) Φ= Φ max sin (wt) e= -N*(dφ/dt) DC Machines DC MOTOR Mechanical force a conductor generate F= BLI newtons B= magnetic flux density(Telsa) L= length of conductor (m) I = current in conductor (a) DC GENERATOR Electromotive force a conductor generate e= BLV V= conductor velocity B field (m/s) P eddy = K e f 2 *B m 2 *t 2 watts K e = proportionality constant t=thickness core laminations Transformer ω=2πf= angular frequency (rad/sec) Φ= Φ max cos (wt) AC machines V 1 = E 1 = N 1 = a turn ratio V 2 = E 2 = N 2 1/a current a 2 impedance Input power = output power E 1 I 1 PF 1 = E 2 I 2 PF 2 V 1 I 1 = V 2 I 2 (volt amp) VA V 2 >V 1 step up V 2 <V 1 step down V 2 = V 1 isolation R eq = P/I 2 current known R eq = V 2 / P voltage known Z = R eq + jX eq R eq = R 1 + R 2 *a 2 X eq = X 1 + X 2 *a 2 I= V/Z η= P out / (P out + P losses ) =PF/(PF+R eq + R eqpu )*100% %Reg = {[(cosθ + R eq ) 2 + (sinθ + X eq ) 2 ] 1/2-1}*100% 3phase Induction Motor s = (n s – n r )/ n s per unit (pu) slip speed of...
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patel cheat sheet - Magnetic Circuits φ = N*I(L/μ*A =...

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