NEETS 15 ch 1,4

Question 1

What is the name given to a variety of rotary electromechanical, position sensing devices?

Answer 1

The synchro

Question 2

What is the primary purpose of a synchro system?

Answer 2

Precise and rapid transmission of data between equipment and stations.

Question 3

Name the two general classifications of synchro systems.

Answer 3

Torque and control.

Question 4

What is the difference between a torque synchro and a control synchro?

Answer 4

A torque synchro is used for light loads and a control synchro is used in systems desired to move
heavy loads.

Question 5

Using table 1-1, name two synchros that provide a mechanical output.

Answer 5

The torque receiver (TR) and the torque differential receiver (TDR).

Question 6

What does the code 26V-11TX4D mean on a synchro nameplate?

Answer 6

It is the third modification of a 26-volt 400-hertz (torque) synchro transmitter whose bodydiameter is between 1.01 and 1.10 inches.

Question 7

Which of the two synchro designation codes is indicated by 5DG on a synchro nameplate?

Answer 7

The Navy prestandard designation code.

Question 8

On the synchro schematic symbol, what indicates the angular displacement of the rotor?

Answer 8

The position of the arrow.

Question 9

What are the two major components of a synchro?

Answer 9

The rotor and the stator.

Question 10

Which of the two main types of rotors can have either a single winding or three Y-connected
windings?

Answer 10

The drum or wound rotor

Question 11

How does the stator receive its voltage?

Answer 11

By the magnetic coupling from the rotor

Question 12

Where are the external connections made on standard synchros?

Answer 12

At the terminal board

Question 13

What major factors determine the load capacity of a torque-synchro transmitter?

Answer 13

. The number and type of synchro receivers, the mechanical loads on these receivers and the
operating temperatures of both the transmitter and receivers

Question 14

Define the term “torque.”

Answer 14

A measure of how much load a machine can turn.

Question 15

What unit of measurement refers to the torque of a synchro transmitter?

Answer 15

Ounce-inches.

Question 16

What type of equipment normally uses 26-volt 400-hertz synchros?

Answer 16

. Aircraft.

Question 17

When will a synchro generate more heat than it is designed to handle?

Answer 17

When it is overloaded.

Question 18

How do synchros differ from conventional transformers?

Answer 18

Synchros have one primary winding that can be turned through 360º and three secondary
windings spaced 120º apart.

Question 19

Describe the zero-position of a synchro transmitter.

Answer 19

The transmitter is in its zero-position when the rotor is aligned with the S2 stator winding.

Question 20

When is the maximum voltage induced into a stator coil?

Answer 20

. When the rotor coil is aligned with the stator coil

Question 21

What three factors determine the amplitude of the voltage induced into a stator winding?

Answer 21

The amplitude of the primary voltage, the turns ratio, and the angular displacement between the
rotor and the stator winding

Question 22

What is the physical difference between a synchro transmitter and a synchro receiver?

Answer 22

A synchro receiver uses some form of damping to retard excessive oscillations or spinning.

Question 23

What method is used to prevent oscillations in large synchro units?

Answer 23

Mechanical damping.

Question 24

What two components make up a simple synchro transmission system?

Answer 24

A synchro transmitter and a synchro receiver.

Question 25

What leads in a simple synchro system are connected to the ac power line?

Answer 25

The rotor leads.

Question 26

What is the relationship between the transmitter and receiver stator voltages when their rotors are in correspondence?

Answer 26

The voltages are equal and oppose each other

Question 27

What is the name given to the angle through which a transmitters rotor is mechanically rotated?

Answer 27

Signal.

Question 28

What two receiver leads are reversed to reverse the rotor's direction of rotation?

Answer 28

. 1 and S3.

Question 29

What is the most likely problem if the transmitter shaft reads 0º when the receiver shaft indicates 180º?

Answer 29

. The rotor leads on either the transmitter or the receiver are reversed.

Question 30

What is the purpose of using differential synchros instead of regular synchros?

Answer 30

. Differential synchros can handle more signals than regular synchros and also perform addition and subtraction functions

Question 31

What are the two types of differential synchros?

Answer 31

The TDX and the TDR

Question 32

Other than their physical differences, what is the major difference between a TDX and a TDR?

Answer 32

Their application: a TDX has one electrical and one mechanical input with an electrical output.

Question 33

What determines whether a differential synchro adds or subtracts?

Answer 33

The way the differential synchro is connected in a system is the deciding factor on whether the unit adds or subtracts its inputs

Question 34

In a TDX system when does the TR rotor follow the TX rotor exactly?

Answer 34

When the TDX rotor is on 0º.

Question 35

What is the angular position of a TX rotor when it is pointing toward the S1 winding? (Hint. Remember synchros are labeled counter clockwise from 0º.

Answer 35

240º.

Question 36

In a TDX system with standard synchro connections, the TX rotor is at 120º and the TDX rotor is at 40º. What position will the TR indicate?

Answer 36

. 80º.

Question 37

What connections in a TDX system are reversed to set up the system for addition?

Answer 37

The S1 and S3 leads are reversed between the TX and the TDX, and the R1 and R3 leads are reversed between the TDX rotor and the TR.

Question 38

What connections in a TDR system are reversed to set up the system for addition?

Answer 38

The R1 and R3 leads between the TDR rotor and the TX to which it is connected

Question 39

In a TDR system connected for addition in what direction will the TDR rotor field turn when the TX rotor to which it is connected turns counterclockwise?

Answer 39

Clockwise.

Question 40

What type of synchro is used in systems requiring large amounts of power and a high degree of accuracy?

Answer 40

A control synchro

Question 41

What are the three types of control synchros?

Answer 41

. CX, CT, and CDX.

Question 42

How do the CX and CDX differ from the TX and TDX?

Answer 42

. The CX and CDX have higher impedance windings

Question 43

What three things prevent a CT rotor from turning when voltages are applied to its stator windings?

Answer 43

The rotor is specially wound, it is never connected to an ac supply, and its output is always applied to a high-impedance load

Question 44

When a CT is on electrical zero, what is the relationship between its rotor and the S2 winding?

Answer 44

They are perpendicular to each other

Question 45

What is the amplitude and voltage induced into the rotor when the CX is turned 90º while the CT remains on electrical zero?

Answer 45

The voltage is maximum and in phase with the ac excitation voltage to the CX.

Question 46

What is the name given to the electrical output of a CT?

Answer 46

Error signal.

Question 47

In a control synchro system, when is the output of the CT reduced to zero?

Answer 47

When the CX and CT rotors are in correspondence.

Question 48

What is the purpose of the synchro capacitor?

Answer 48

To improve overall synchro system accuracy by reducing stator currents

Question 49

What type of synchros usually require the use of synchro capacitors?

Answer 49

TDXs, CDXs, and Cts.

Question 50

What type of current is eliminated by synchro capacitors?

Answer 50

Magnetizing current.

Question 51

How are synchro capacitors connected in a circuit?

Answer 51

They are delta-connected across the stator windings

Question 52

Why are synchro capacitors placed physically close to differentials transmitters and CTs?

Answer 52

To keep the connections as short as possible in order to maintain system.

Question 53

What is the name given to the synchro system that transmits data at two different speeds?

Answer 53

A dual or double-speed synchro system.

Question 54

What is the main reason for using a multispeed synchro system instead of a single-speed synchro system?

Answer 54

. Greater accuracy without the loss of self-synchronous operation.

Question 55

In a dual-speed synchro system what determines the two specific speeds at which the data will be transmitted?

Answer 55

The gear ratio between the two transmitters.

Question 56

What type of synchro system is used to transmit very large quantities?

Answer 56

A tri-speed synchro system

Question 57

What is the disadvantage of using a double receiver instead of two individual receivers?

Answer 57

If one of the receivers goes bad the entire unit must be replaced

Question 58

What is the purpose of "stickoff voltage"?

Answer 58

It is used in synchro systems to prevent false synchronizations

Question 59

What is the reference point for alignment of all synchro units?

Answer 59

Electrical zero.

Question 60

What is the most accurate method of zeroing a synchro?

Answer 60

The voltmeter method.

Question 61

What is the purpose of the coarse setting of a synchro?

Answer 61

.It ensures the synchro is on 0º, not 180º

Question 62

When is a synchro receiver (TR) properly zeroed?

Answer 62

A TR is zeroed when electrical zero voltages exist across its stator windings at the same time its rotor is on zero or on its mechanical reference position

Question 63

What should a voltmeter read when a TX is set on coarse zero?

Answer 63

Approximately 37 volts

Question 64

What precaution should you take when you use 115 volts to zero a differential?

Answer 64

Never leave the circuit energized for more than 2 minutes

Question 65

Why should a synchro be rechecked for zero after it is clamped down?

Answer 65

. To ensure that it did not move off zero while it was being clamped

Question 66

What is the output voltage of a CT when it is set on electrical zero?

Answer 66

Zero or minimum voltage.

Question 67

When you zero a multispeed synchro system which synchro should you zero first?

Answer 67

. The coarse synchro

Question 68

What method of zeroing a synchro is perhaps the fastest but NOT necessarily the most accurate?

Answer 68

The electrical lock method

Question 69

What restrictions are placed on the use of the electrical lock method?

Answer 69

It can be used only if the leads of the synchro are accessible and the rotor is free to turn.

Question 70

When you zero a synchro with a synchro tester, what is indicated by a jump in the synchro tester's dial when the S1 and S3 leads are momentarily shorted?

Answer 70

. The synchro under test is not on electrical zero

Question 71

What should you do with a synchro that has a bad set of bearings?

Answer 71

Replace it.

Question 72

Name two types of trouble you would expect to find in a newly installed synchro system.

Answer 72

Improper wiring and misalignment

Question 73

What type of indicator is usually placed in the stator circuit of a torque synchro system?

Answer 73

An overload indicator.

Question 74

What is the most probable cause of trouble in a synchro system that has all of its receivers reading incorrectly?

Answer 74

The transmitter or main bus

Question 75

If an ac voltmeter is connected between the S2 and S3 windings on a TX, at what two rotor positions should the voltmeter read maximum voltage?

Answer 75

150º and 330º

Question 76

What precaution should you take when substituting a synchro tester in a circuit for a transmitter?

Answer 76

Use only one receiver so as not to overload the tester.

Question 77

What is a servo?

Answer 77

Direction of rotation and amount of torque.

Question 78

Compare the power sources of synchros and step-transmission systems.

Answer 78

Synchros use ac; step transmission uses dc.

Question 79

A step transmitter is a modification of what electrical device?

Answer 79

Rotary switch

Question 80

What type of mathematical problem is solved by resolvers?

Answer 80

Right-triangle, or trigonometric, problems.