1 FOUNDATION DEGREE Course FE 101 and SC1107 COMPLEX R,L and C LOADS and the POWER WAVEFORMS
2 So now we have to deal with more than just resistance in a load. In fact in most practical loads there is always a mixture of resistance, inductance and capacitance, which means we are dealing with impedance loads. POWER IN COMPLEX LOADS
3 So remember the basics of impedance and the impedance triangle from our earlier lessons ? COMPLEX LOADS IMPEDANCE Is the total ‘resistance’ to current that a circuit displays when subjected to alternating current. It is made up of Resistance (R) Reactance (X) as a result of inductance and capacitance.
4 IMPEDANCE
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9 A mixed Resistive and Inductive Reactance Circuit
10 A mixed Resistive and Capacitive Reactance Circuit
11 A mixed Resistive, Inductive & Capacitive Reactance or Impedance Circuit
12 The Impedance Triangle The cosine of the angle ( cos ) = the power factor ( p.f ) of the circuit.
13 The Impedance Triangle – developed to a power triangle by multiplying each side by I 2 Again the cosine of the angle ( cos ) = the power factor ( p.f ) of the circuit.
14 Alternative Development of the Power Triangle using the real and quadrature components of the load current with Vs the supply voltage as the reference Vs 0 O Again the cosine of the angle ( cos ) = the power factor ( p.f ) of the circuit.
15 The Power Triangle As before the cosine of the angle ( cos ) = the power factor ( p.f ) of the circuit.
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17 Power Waveform for a purely Resistive Load 230V, R = 2.0 , X L = 0 , = 0 O cos (p.f.) = 1.0
18 Power Waveform for an Impedance Load 230V, R = 2.0 , X L = 2.0 , = - 45 O cos (p.f.) = lag
19 Power Waveform for a purely Inductive Load 230V, R = 0 , X L = 2.0 , = -90 O cos (p.f.) = 0
20 Single –phase Power – Example calculation