1. 1 FOUNDATION DEGREE Course FE 101 and SC1107 COMPLEX R,L and C LOADS and the POWER WAVEFORMS

2. 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. 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. 4 IMPEDANCE

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9. 9 A mixed Resistive and Inductive Reactance Circuit

10. 10 A mixed Resistive and Capacitive Reactance Circuit

11. 11 A mixed Resistive, Inductive & Capacitive Reactance or Impedance Circuit

12. 12 The Impedance Triangle The cosine of the angle  ( cos  ) = the power factor ( p.f ) of the circuit.

13. 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. 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. 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. 17 Power Waveform for a purely Resistive Load 230V, R = 2.0 , X L = 0 ,  = 0 O  cos  (p.f.) = 1.0

18. 18 Power Waveform for an Impedance Load 230V, R = 2.0 , X L = 2.0 ,  = - 45 O  cos  (p.f.) = 0.7071 lag

19. 19 Power Waveform for a purely Inductive Load 230V, R = 0 , X L = 2.0 ,  = -90 O  cos  (p.f.) = 0

20. 20 Single –phase Power – Example calculation