RELATED DEVICES

LEARNING OBJECTIVES

Upon completion of this chapter, you should be able to:

RELATED DEVICES

Some other devices that logically should be included in this module are the IC synchros, step motors, and resolvers. These are all electromagnetic devices used in various shipboard and aircraft applications. They can be considered as second cousins of the synchro.

IC SYNCHROS

The engine order telegraph, steering telegraph, rudder-angle indicator, and similar position-indicating systems used on naval ships are usually simple synchro systems. Some ships, however, use IC synchros to transfer such information. These units operate on the same general principle as the synchros we discussed in chapter 1.

The interior communication synchro (IC synchro) is gradually being phased out and replaced by standard synchros when replacement is required. However, you will still find some IC synchros in use today. For that reason, you will find some background information on their purpose and theory to be beneficial. We will present these synchros in very basic form in the following paragraphs.

Because of their construction, IC synchros are sometimes called reversed synchros. The primary winding, consisting of two series-connected coils, is mounted physically on the stator. The secondary, consisting of three Y-connected coils, is mounted physically on the rotor. This is shown schematically in figure 4-1.

Figure 4-1. - IC synchro schematic diagrams.

IC synchros operate on the same principles of interacting magnetic fields as other synchros, but differ in direction of shaft rotation and amount of torque obtainable. When an IC transmitter and IC receiver are connected in parallel as shown in view A of figure 4-2, the shaft of the IC receiver follows the rotation of the IC transmitter shaft. In view B, the IC transmitter is replaced by a synchro transmitter; the IC receiver shaft now turns in a direction opposite to that of the synchro transmitter. Voltages that cause counterclockwise rotation of a standard synchro shaft cause clockwise rotation of an IC synchro shaft. When it is desirable to have the IC synchro receiver turn in an opposite direction from that of the transmitter, the connections are as shown in view C. For a standard synchro receiver to follow the rotation of an IC transmitter, their connections must be made as shown in view D.

Figure 4-2A. - IC versus standard synchro connections.

Figure 4-2B. - IC versus standard synchro connections.

Figure 4-2C. - IC versus standard synchro connections.

Figure 4-2D. - IC versus standard synchro connections.

The torque obtainable from either an IC synchro or a standard synchro is determined by the magnetizing power, which is limited by the allowable temperature rise. When the stator is energized, as in IC synchros, the magnetizing power can be increased with a resulting larger torque. The reason for this is that the losses are dissipated in the form of heat around the outer shell of the IC transmitter or receiver. In standard synchros, this heat loss is dissipated through the rotor, the air gap, and then the outer shell to the surrounding air.

The electrical zero position for an IC synchro is the position where rotor coil R2 is aligned with the stator as shown in figure 4-1. To zero an IC synchro, apply the same general theory as we described for other synchros.

For further information on IC synchro replacement, alignment, and theory, refer to Military Handbook, Synchros, Description and Operation, (MIL-HDBK-225A).

Q.1 What two characteristics of IC synchros cause them to differ from standard synchros?