(Phasor Diagram of Single Phase Induction Type Energy Meter)
Let , V = applied voltage I = load current ϕ = phase angle of load IP = pressure coil current Δ = phase angle between supply voltage and pressure coil flux f = frequency Z = impedence of eddy current paths α = phase angle of eddy current paths Eep = eddy emf induced by flux Φp Iep = eddy current due to flux Φp Ees = eddy emf induced by flux Φs Ies = eddy current due to flux ΦsNet driving torque,Td ∝ Φp Φs (f/Z) sinβ cosαTd = K1 Φp Φs (f/Z) sinβ cosαWhere ,k1 = a constant,β = phase angle between fluxes Φp and Φs ,Φs = (Δ- ϕ)
• Thus , Driving Torque , Td = K1 Φp Φs (f/Z) sin(Δ- ϕ) cosα• But Φp ∝ V and Φs ∝ I,• ∴ Td = K2 V I (f/Z) sin(Δ- ϕ) cosα• For constants f , Z and α ,• Td = K3 V I sin(Δ- ϕ)• If N is the steady speed, braking torque• Tb = K 4 N• At steady speed , driving torque = braking torque,• ∴ K3 V I sin(Δ- ϕ) = K4 NThus, N = K V I sin(Δ- ϕ) andfor Δ = 90°i.e., N = K V I sin(90°- ϕ)
• N = K V I cos ϕ• Now V I cos ϕ = P (Power)• Or N = K x (Power)Total number of revolutions = ∫ N dt = K x ∫ (Power) dt = K x (energy)
Errors - Incorrect magnitude of fluxes, Incorrect phase angles, Changes in strength of brake magnet, Changes in disc resistance, Abnormal friction of moving parts Adjustments - Preliminary light load adjustment, Light load adjustment, Creep adjustment
A particular slide catching your eye?
Clipping is a handy way to collect important slides you want to go back to later.