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EEM PRESENTATION
ON INDUCTION TYPE ENERGY METER
PRESENTED BY -
(Single Phase Induction Meter)
Introduction -
Construction -
Driving system, Moving system, Braking syatem, and Registering system
Theory & Operation -
(Working)
(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 Φs Net 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 = K4 N
• At steady speed , driving torque = braking torque,
• ∴ K3 V I sin(Δ- ϕ) = K4 N
Thus, N = K V I sin(Δ- ϕ) and for 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