Synchro Operation

revolve in response to the same reading, a vernier effect

dial window, four indicator lights, and a double fuse

is achieved so that a higher accuracy is obtained

holder are mounted on the front access door. A

schematic diagram of the subassembly is provided on

Synchro Operation

the inside of the front access door.

Terminal boards on the inside bottom of the case

The synchro transmitter resembles a small bipolar

serve as a common junction for connecting the ship's

3-phase motor. The stator is wound with a three-circuit

wiring. Access plates on both sides of the synchro signal

Y-connected winding. The rotor is wound with a single-

amplifier provides for external cabling. Stuffing tubes

circuit winding. Electrically, the synchro acts as a trans-

are mounted to these plates as required at installation,

former; all voltages and currents are single phase. By

and the external cabling is run through the stuffing tubes.

transformer action, voltages are induced in the three

Speed changes from 1 speed to 2 speed and vice

elements of the stator winding, the magnitude de-

versa are made by installing change gears. These gears

pending upon the angular position of the rotor.

are not normally furnished with the synchro signal

The synchro receiver is constructed essentially the

amplifier. Both the E- and F-type units have a dial with

same, both mechanically and electrically, except it is

two scales, one on each side. One scale is calibrated

provided with a mechanism for dampening oscillations.

every degree from 0 to 360 and is driven at 1 speed,

Consider the simplest synchro transmission system,

when 1 speed is used. The other scale is calibrated 60

where the transmitter and receiver units are connected

either side of zero (300 to 0 and 0 to 60), and this

as shown on figure 2-5. If the receiver rotor were free to

scale is used when a 2-speed transmission is needed. The

turn, it would take a position where induced stator

dial turns over when changing from 1 speed to 2 speed

voltages would be equal to the transmitter voltages.

or vice versa.

Under such a condition there is no current flow. How-

When either unit is operating from a low 1- or

ever, if the transmitter rotor was displaced by any angle,

2-speed input, you must make some minor wiring

the stator voltage balance would be altered and current

changes. Connections between the terminals on the

would flow in the stator windings. This current flow

plug-in damping unit should be changed from those

would set up a two-pole torque, turning the receiver

shown for 1 and 2 speed and 36 sped to those shown

rotor to a position where the induced stator voltages

for 1 or 2 speed. This connects the normally dis-

would again be equal. Therefore, any motion given to

connected low-speed synchro control transformer.

the rotor of one unit would be transmitted to the rotor of

These connections also remove the antistickoff voltage,

the other unit where it is duplicated thereby setting up

which will be discussed later in this chapter.

a system of electrically transmitted mechanical motion.

The synchro signal amplifier transmission system

PRINCIPLES OF OPERATION

depends upon the type of transmitter described in the

previous paragraphs, but its receiver is a synchro control

The synchro signal amplifier is actually a synchro

transformer. The purpose of the synchro control trans-

data repeater. It accepts synchro data from remote trans-

former is to supply, from its rotor terminals, an ac

mitters, aligns associated output synchros to electrical

voltage whose magnitude and phase polarity depend

correspondence with the remote transmitters, and re-

upon the position of the rotor and voltages applied to its

transmits the data to other equipment. Synchro trans-

stator windings. Since its rotor winding is not connected

mission is increased by using larger output synchros

to the ac supply, it does not induce voltage in the stator

than the remote transmitter.

coils. As a result, the stator current is determined by the

Since the output synchros are driven to electrical

high impedance at the windings and it is not affected

correspondence with the remote transmitters by gearing,

appreciably by the rotor's position. Also, there is no

a power supply of a different frequency may be used for

detectable current in the rotor and, therefore, no torque

the output synchros. This gives the synchro signal

striving to turn the rotor. The synchro control trans-

amplifier another attribute, as a frequency converter.

former rotors cannot on their own accord turn to a

position where the induced currents are once again of

A higher accuracy is obtained from a synchro signal

balanced magnitude. The synchro amplifier cycle of

amplifier with a 36-speed input than would be obtained

operation must take place to turn the rotor of the synchro

from a l-speed input. By virtue of the 36 speed revolving

control transformer.

36 times the angular distance that the 1 speed would

2-10