OTHER ELECTRICAL MEASURING DEVICESTest Instruments & Measuring DevicesPowerFactorMeterA power factor meter is a type of electrodynamometer movement when it is made with twomovable coils set at right angles to each other. The method of connection of this type of powerfactor meter, in a 3f circuit, is shown in Figure 14. The two stationary coils, S and S1, areconnected in series in Phase B. Coils M and M1 are mounted on a common shaft, which is freeto move without restraint or control springs. These coils are connected with their series resistorsfrom Phase B to Phase A and from Phase B to Phase C. At a power factor of unity, onepotential coil current leads and one lags the current in Phase B by 30°; thus, the coils arebalanced in the position shown in Figure 14. A change in power factor will cause the currentof one potential coil to become more in phase and the other potential coil to be more out ofphase with the current in Phase B, so that the moving element and pointer take a new positionof balance to show the new power factor.Figure 14 3f Power Factor Meter SchematicGroundDetectorThe ground detector is an instrument which is used to detect conductor insulation resistance toground. An ohm meter, or a series of lights, can be used to detect the insulation strength of anungrounded distribution system. Most power distribution systems in use today are of thegrounded variety; however, some ungrounded systems still exist.ES-14 Page 24 Rev. 0
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