Figure 1-30.—The use of a synchro capacitor with a CT

1-40 Figure 1-29.—The synchro capacitor. The three delta-connected capacitors, shown in figure 1-29, usually come as a unit mounted in a case with three external connections. The entire unit is called a SYNCHRO CAPACITOR. The synchro capacitor is made in many sizes to meet the requirements of all sizes of standard differentials and control transformers. The synchro capacitor is rated by its total capacity, which is the sum of the individual capacities in the unit. Figure 1-30 shows how a synchro capacitor affects the operation of a control synchro system. In this figure, the capacitor is placed between the CX and the CT. Two current meters are also placed in the circuit to show the effect the capacitor has on stator current. The meter connected between the capacitor and the CT reads normal stator current, 32 milliamperes (mA). This current would normally flow in the stator of the CX if the synchro capacitor were not connected. The other meter reads 10 mA, which is what is left of the original stator current after the magnetizing current has been canceled by the synchro capacitor. By reducing the current drain on the transmitter, the sensitivity and accuracy of the system increase. Figure 1-30.—The use of a synchro capacitor with a CT. Figure 1-31 shows another application of a synchro capacitor; this time in a differential system in this circuit the capacitor is placed between a TX and a TDX. The meter readings show the same comparison between currents as in the previous paragraph. The only significant difference between this circuit and the one in figure 1-30 is that the differential draws more stator current than the CT.