Figure P10.61 shows the equivalent circuit for a typical

Chapter 10, Problem P10.61

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Figure P10.61 shows the equivalent circuit for a typical automotive battery charging system. The three-phase delta-connected source represents the stator coils of the alternator. (Three-phase ac sources are discussed in Section 5.7. Actually, the alternator stator is usually wye connected, but the terminal voltages are the same as for the equivalent delta.) Not shown in the figure is a voltage regulator that controls the current applied to the rotor coil of the alternator and, consequently, Vm and the charging current to the battery. a. Sketch the load voltage vL(t) to scale versus time. Assume ideal diodes and that Vm is large enough that current flows into the battery at all times. (Hint: Each 507 source and four of the diodes form a fullwave bridge rectifier.) b. Determine the peak-to-peak ripple and the average load voltage in terms of Vm. c. Determine the value of Vm needed to provide an average charging current of 30 A. d.What additional factors would need to be considered in a realistic computation of Vm? vAB vBC vCA + + + 12 V 0.1 A C B + + vL vAB = Vm cos(vt) vBC = Vm cos(vt 120) vCA = Vm cos(vt + 120) Figure P10.61 Idealized model of an automotive battery-charging system.