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SYNCHRO CLASSIFICATION

Synchros work in teams. Two or more synchros interconnected electrically form a synchro system. There are two general classifications of synchro systems - TORQUE SYSTEMS AND CONTROL SYSTEMS. Torque-synchro systems use torque synchros and control-synchro systems use control synchros. The load dictates the type of synchro system, and thus the type of synchro.

Torque-synchro systems are classified "torque" because they are mainly concerned with the torque or turning force required to move light loads such as dials, pointers, or similar indicators. The positioning of these devices requires a relatively low amount of torque. Control synchros are used in systems that are designed to move heavy loads such as gun directors, radar antennas, and missile launchers.

In addition to the two general classifications, synchros are grouped into seven basic functional classes as shown in table 1-1.  Four of these are the torque type and three are the control type. Each synchro is described in the table by name, abbreviation, input, output, and the other synchro units that may be connected to it. Generally, torque and control synchros may not be interchanged. The functional operation of each of these seven synchros is covered later in this text.

Table 1-1. - Synchro Information

FUNCTIONAL CLASSIFICATION ABBREVIATION INPUT OUTPUT
Torque transmitter TX Mechanical input to rotor (rotor energized from AC source) Electrical output from stator representing angular position of rotor to TDX, TDR, or TR.
Control transmitter CX Same as TX Same as TX except it is supplied to CDX or CT
Torque differential transmitter TDX Mechanical input to rotor, electrical input to stator from TX or another TDX. Electric output from rotor representing algebraic sum or difference between rotor angle and angle represented by electrical input to TR, TDR, or another TDX.
Control differential transmitter CDX Same as TDX except electrical input is from CX or another CDX. Same as TDX except output to CT or another CDX.
Torque receiver TR Electrical input to stator from TX or TDX. (Rotor energized from AC source) Mechanical output from rotor. Note: Rotor has mechanical inertia damper.
Torque differential receiver TDR Electrical input to stator from TX or TDX, another electrical input to rotor from TX or TDX. Mechanical output from rotor representing algebraic sum or difference between angles represented by electrical inputs. Has inertia damper.
Control transformer CT Electric input to stator from CX or CDX, mechanical input to rotor. Electrical output from rotor proportional to the sine of the angle between rotor position and angle represented by electrical input to stator. Called error signal.
Torque receiver TRX Depending on application, same as TX. Depending on application, same as TX or TR.

Synchros are also classified according to their operating frequency.

This classification was brought about by the development of the 400-Hz synchro.

Prior to this time, the 60-Hz synchro was the only one in use. Synchro operating frequencies are covered in detail in the section on synchro characteristics.

Q.3 Name the two general classifications of synchro systems. answer.gif (214 bytes)
Q.4 What is the difference between a torque synchro and a control synchro? answer.gif (214 bytes)
Q.5 Using table 1-1, name two synchros that provide a mechanical output. answer.gif (214 bytes)

STANDARD MARKINGS AND SYMBOLS

Synchros used in the Navy can be grouped into two broad categories:

  • MILITARY STANDARD SYNCHROS and PRESTANDARD NAVY SYNCHROS. Military standard synchros conform to specifications that are uniform throughout the armed services.
  • New varieties of equipment use synchros of this type. Prestandard synchros were designed to meet Navy, rather than servicewide, specifications. Each category has its own designation code for identification.

Military Standard Synchro Code

The military standard designation code identifies standard synchros by their physical size, functional purpose, and supply voltage characteristics. The code is alphanumerical and is broken down in the following manner. The first two digits indicate the diameter of the synchro in tenths of an inch, to the next higher tenth. For example, a synchro with a diameter of 1.75 inches has the numeral 18 as its first two digits. The first letter indicates the general function of the synchro and of the synchro system-C for control or T for torque. The next letter indicates the specific function of the synchro, as follows:

LETTER DEFINITION
D Differential
R Receiver
T Transformer
X Transmitter

If the letter B follows the specific function designation, the synchro has a rotatable stator. The last number in the designation indicates the operating frequency-6 for 60 Hz and 4 for 400 Hz. The upper-case letter following the frequency indicator is the modification designation. The letter "A" indicates that the synchro design is original. The first modification is indicated by the letter "B." Succeeding modifications are indicated by the letters "C," "D," and so on, except for the unused letters "I," "L," "O," and "Q."

For example, an 18TR6A synchro is an original design, 60-Hz torque receiver with a diameter of between 1.71 and 1.80 inches.

A synchro designated 16CTB4B is the first modification of a 400-Hz control transformer with a rotatable stator and a diameter of between 1.51 and 1.60 inches.

All standard synchros are labeled with such a code. Synchros used in circuits supplied by 26 volts are classified in the same way, except that the symbol 26V is prefixed to the designator (for example, 26V-16CTB4A). Otherwise, a 115 volts source is assumed for the synchro system.

Navy Prestandard Synchro Code

The Navy prestandard designation code identifies prestandard synchros by size and function, using a number and letter combination. Unlike the standard code, the number does not indicate directly the diameter of the synchro. The number merely represents the approximate size of the synchro, increasing as the size increases. The approximate size and weight of the five most common sizes are shown in the following table.

SIZE APPROX. DIAMETER  APPROX. LENGTH APPROX WEIGHT
1 2 1/4 in 4 in 2 lb
3 3 1/10 in 5 3/8 in 3 lb
5 3 3/8 to 3 5/8 in 6 1/2 in 5 lb
6 4 1/2 in 7 in 8 lb
7 5 3/4 in 9 in 18 lb

Note that prestandard size 1 is approximately the same size as standard size 23 (2.21 to 2.30 inches in diameter). Prestandard size 3 is approximately the same size as standard size 31. Prestandard size 5 is approximately the same size as standard size 37.

The letters used in the prestandard coding system indicate the function, mounting, or special characteristics of the synchro as shown in the following chart.

LETTER DEFINITION
G Transmitter
F Flange Mounted Receiver (this letter is normally omitted if letters other than H or S occur in type designation)
D Differential Receiver
DG Differential Transmitter
CT Control Transformer
H High-Speed Unit
B Bearing Mounted Unit
N Nozzle Mounted Unit
S Special Unit

Navy prestandard synchros are rarely used today. They have been replaced by the standard synchro. However, by being familiar with the prestandard coding system, you will be able to identify the older synchros and make correct replacements if necessary.

Q.6 What does the code 26V-11TX4D mean on a synchro nameplate? answer.gif (214 bytes)
Q.7 Which of the two synchro designation codes is indicated by 5DG on a synchro nameplate? answer.gif (214 bytes)




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