When a synchro capacitor is used, it is always placed physically close to the differential or control
transformer whose current it corrects. This is done to keep the connections as short as possible, because
high currents in long leads increase the transmitter load and reduce the accuracy of the system.
We must stress that the synchro capacitor should never be used in a simple transmitter-receiver
system. This is because stator currents in this system are zero at correspondence and the addition of a
synchro capacitor would only increase the stator current and throw the system out of balance.
Q-48. What is the purpose of the synchro capacitor?
Q-49. What type of synchros usually require the use of synchro capacitors?
Q-50. What type of current is eliminated by synchro capacitors?
Q-51. How are synchro capacitors connected in a circuit?
Q-52. Why are synchro capacitors placed physically close to differentials transmitters and CTs?
MULTISPEED SYNCHRO SYSTEMS
The data to be transmitted is another important factor that we must consider when we discuss the
accuracy of a synchro system. If this data covers a wide range of values, the basic synchro system is
unable to detect any small changes in the data. When this happens, the accuracy of the system decreases.
Because of this difficulty, multispeed synchro systems were developed. They handle this type of data very
effectively and still maintain a high degree of accuracy.
Multispeed synchro systems use more than one speed of data transmission. The speed of data
transmission is, simply, the number of times a synchro transmitter rotor must turn to transmit a full range
of values. For example, a system in which the rotors of synchro devices turn in unison with their input
and output shafts is commonly called a 1-speed data transmission system. In this system, the transmitter's
rotor is geared so that 1 revolution of the rotor corresponds to 1 revolution of the input. Until now, the
discussion of synchro systems has dealt exclusively with this 1-speed system.
In a 36-speed data transmission system, the rotor of the synchro transmitter is geared to turn through
36 revolutions for 1 revolution of its input. Units transmitting data at one speed are frequently called 1-
speed synchros; a unit transmitting data at 36-speed would be a 36-speed synchro, and so forth.
It is quite common in synchro systems to transmit the same data at two different speeds. For
example, ship's course information is usually transmitted to other locations on a ship at 1-speed and 36-
speed. A system in which data is transmitted at two different speeds is called a dual- or double-speed
system. Sometimes a dual-speed system will be referred to by the speeds involved, for example a 1- and
In summary, the speed of data transmission is referred to as 1-speed, 2-speed, 36-speed, or some
other definite numerical ratio. To indicate the number of different speeds at which data is transmitted,
refer to the system as being a single-speed, dual-speed, or tri-speed synchro system.
SINGLE-SPEED SYNCHRO SYSTEM
If the data to be transmitted covers only a small range of values, a single-speed system is normally
accurate enough. However, in applications where the data covers a wide range of values and the accuracy
of the system is most important, the 1-speed system is not adequate enough and must be replaced by a