JAMES W NILSSON SUSAN A RIEDEL ELECTRIC CIRCUITS

JAMES W. NILSSON & SUSAN A. RIEDEL ELECTRIC CIRCUITS EIGHTH EDITION

CHAPTER 11 BALANCED THREE –PHASE CIRCUITS © 2008 Pearson Education

CONTENTS 11. 1 Balanced Three-Phase Voltages 11. 2 Three-Phase Voltage Sources 11. 3 Analysis of the Wye-Wye Circuit 11. 4 Analysis of the Wye-Delta Circuit 11. 5 Power Calculations in Balanced Three. Phase Circuits 11. 6 Measuring Average Power in Three. Phase Circuits © 2008 Pearson Education

11. 1 Balanced Three-Phase Voltages A basic three-phase circuit © 2008 Pearson Education

11. 1 Balanced Three-Phase Voltages The abc (positive) sequence The abc (negative) sequence Phasor diagrams of a balanced set of three-phase voltages © 2008 Pearson Education

11. 2 Three-Phase Voltage Sources A sketch of a three-phase voltage source © 2008 Pearson Education

11. 2 Three-Phase Voltage Sources ØThe two basic connections of an ideal three -phase source. A Y-connected source A ∆-connected source © 2008 Pearson Education

11. 2 Three-Phase Voltage Sources A model of a three-phase source with winding impedance: (a) A Y-connected source (b) A ∆-connected source © 2008 Pearson Education

11. 3 Analysis of the Wye-Wye Circuit A three-phase Y-Y system © 2008 Pearson Education

11. 3 Analysis of the Wye-Wye Circuit A single-phase equivalent circuit ØA single-phase equivalent circuit is used to calculate the line current and the phase voltage in one phase of the Y-Y structure. The a-phase is normally chosen for this purpose. © 2008 Pearson Education

11. 3 Analysis of the Wye-Wye Circuit Line-to-line and line-to-neutral voltages © 2008 Pearson Education

11. 3 Analysis of the Wye-Wye Circuit Ø Phasor diagrams showing the relationship between line-to-line and line-to-neutral voltages in a balanced system. The abc sequence The acb sequence © 2008 Pearson Education

11. 4 Analysis of the Wye-Delta Circuit ØRelationship between three-phase deltaconnected and wye-connected impedance. A single-phase equivalent circuit © 2008 Pearson Education

11. 4 Analysis of the Wye-Delta Circuit A circuit used to establish the relationship between line currents and phase currents in a balanced ∆ load © 2008 Pearson Education

11. 4 Analysis of the Wye-Delta Circuit Ø Phasor diagrams showing the relationship between line currents and phase currents in a ∆-connected load. The positive sequence The negative sequence © 2008 Pearson Education

11. 5 Power Calculations in Balanced Three-Phase Circuits ØAverage Power in a Balanced Wye Load A balanced Y load used to introduce average power calculations in three-phase circuits © 2008 Pearson Education

11. 5 Power Calculations in Balanced Three-Phase Circuits Total real power in a balanced three-phase load © 2008 Pearson Education

11. 5 Power Calculations in Balanced Three-Phase Circuits ØComplex Power in a Balanced Wye Load Total reactive power in a balanced three-phase load © 2008 Pearson Education

11. 5 Power Calculations in Balanced Three-Phase Circuits Total complex power in a balanced three-phase load

11. 5 Power Calculations in Balanced Three-Phase Circuits ØPower Calculations in a Balanced Delta Load A Δ-connected load used to discuss power calculations © 2008 Pearson Education

11. 6 Measuring Average Power in Three-Phase Circuits ØA wattmeter measures the average power delivered to a load by using a current coil connected in series with the load and a potential coil connected in parallel with the load. © 2008 Pearson Education

11. 6 Measuring Average Power in Three-Phase Circuits The key features of the electrodynamometer wattmeter © 2008 Pearson Education

11. 6 Measuring Average Power in Three-Phase Circuits A general circuit whose power is supplied by n conductors © 2008 Pearson Education

11. 6 Measuring Average Power in Three-Phase Circuits ØThe total average power in a balanced three-phase circuit can be measured by summing the readings of two wattmeters connected in two different phases of the circuit. © 2008 Pearson Education

11. 6 Measuring Average Power in Three-Phase Circuits A circuit used to analyze the twowattmeter method of measuring average power delivered to a balanced load © 2008 Pearson Education

THE END © 2008 Pearson Education