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Page 343

| Figure 17-12 Single-phase, crossed-coil power factor meter (Courtesy, General Electric Co.) |

| Power-Factor Meter.. |

| An adaptation of the electrodynamometer construction for measuring the power factor is shown in Fig. 17-12. In the so-called crossed-coil type, there is one fixed coil and two moving coils mounted on a common shaft at an angle to one another. The instrument is designed for either single-phase or three-phase service. The connections are shown in Fig. 17-13. |

| Frequency Meter |

| Another adaptation of the electrodynamometer construction for measuring frequency within certain limits is shown in Fig. 17-14. |

| Watt-Hour Meters |

| In the watt-hour meter for measuring electrical energy, a disc takes the place of the movable coil (Fig. 17-15). An electromagnet having two coils is constructed so as to allow the disc to rotate between a pair of poles. One coil is connected to measure current while the other is connected to measure voltage. The magnetic fields created cut the disc, thereby inducing eddy currents within it (Fig. 17-16). The eddy currents, in turn, set up a magnetic field that reacts with the other magnetic fields, causing it to act as a motor. |

| The disc will therefore rotate since it does not have springs to prevent it from doing so. The speed at which it rotates will depend on the power flowing. A train of gears and a set of dials are arranged in a register to count the number of revolutions made by the disc, this number being a measure of the electrical energy. |

| Two types of single-phase watt-hour meters are shown in Fig. 17-17 A and B. Schematic diagrams for single-phase two-wire and three-wire meters are shown in Fig. 17-18. Registers for these meters are made in two types, the conventional and the cyclometer type, both of which are shown in Fig. 17-19. |

| Solid-state technology has made possible adding components to the |

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