NEETS 15 CH 1 SYNCHROS

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What are synchros primarily use for?
Rapid and accurate transmission information between equipment and stations.
What are some of the advantages of Synchros?
Provide speed and accuracy in delivering information.

What ared the two general classifications of synchro systems.
Torque systems

Control systems
Why are torque systems classified "torque".
Because they are mainly concerned with the torque or tturning force required to move light loads such as dials, pointers or similar indicators.
What is the difference between torque and control synchros?
Torque position relative light load amounts and control systems move heavy loads.
In addition to general classifications, how many basic functional classes are synchros grouped?
Seven
How many of the seven are torque type?
Four
Are torque and controls interchangable?
Generally they are not.
What type of input and output do torque transmitters (TX) have?
Mechanical input to the rotor (rotor is energized by an AC source) and electrical output from the stator representing angular position of rotor to TDX, TDR or TR.
Name two syncros that provid a mechanic output.
What type of input and output does the control transmitter (CX) have?
Mechanical input to rotor and electrical output from stator to the CDX or CT.
What type of input and output does the control differential transmitter (CDX) have?
Mechanical input to rotor, electrical input to stator from CX or another CDX and electrical output from rotor representing algebraic sum or difference between rotor angle and angle represented by electrical input to CT or another CDX.
What type of input and output does the torque diffential transmitter (TDX) have?
Mechanical input to rotor, electrical input to stator from CX or another CDX and electrical output from rotor representing algebraic sum or difference between rotor angle and angle represented by electrical input to TR, TDR or another TDX.
What type of input and output does the torque transmitter (TR) have?
Electrical imput to stator from TX or TDX (AC source) and mechanical out from rotor (rotor has mechanical inertial damper)
What type of input and output does the torque differential recever(TDR) have?
Electrical input to stator fro TX or TDX, another electrical input to rotor from TX or TDX and mechanical out from rotor representing algebraic sum or defference between angles represented by electrical imputs. Has inertia damper.
What type of input and output does the control transformer (CT) have?
Electrical input to stator from CX or CDX, mechanical input to rotor and electrical out from rotor proportional to the sine of the angle between rotor position and angle represented by electrical input to stator.
What type of input and output does the torque receiver(TRX) have?
Depending upon application mechanical input to rotor and electrical output from stator to the TDX, TDR or TR.
What is the proportional to the sine of the angle between rotor position and angle represented by electrical input to stator called.
Error Signal
Synchros used by the Navy can be group into two broad categories, what are they?
Military Standard and Prestandard Navy.
What is the purpose of prestandard Navy synchros?
They are designed to meet Navy, rather than servicewide, specifications.
What does military standard designation codes identify about synchros?
Physical size, functional purpose and supply voltage characteristics.
What does the designation 18TR6A signify about the military standard synchro?
It is an original design (A) 60 Hz (6) torque receiver (TR) with a diameter between 1.71 and 1.80 inches.
How are modifications to the original design designated in military standard codes.
By alphabets, B for first modication and C, D and so on for succeeding modifications, except I, L, O, and Q are not used.
If a synchro is used in a circuit supplied by 26V how is it coded?
It is coded the same way, except 26V prefixes the designator i.e. 26V-16CTB4A. A first modication (last B) of a 400 Hz (4) control transformer with a rotable stator (first B)and a diameter of 1.51 to 1.60 inches ( tenth of an inch to the next higher tenth)
What is assumed if no supply voltage is listed in the designation code?
The volt source is 115 volts.
What does the number represent in a prestandard designation?
The approximate size of the synchro.
Size Diam Length Weight
1 2.25 4 2lb
2 3.1 5 3/8 3lb
3
What does the code 26V-11TX4D mean on a synchro nameplate?
Third modification 26 volt 400 hz torque transmitter between 1.01 to 1.10 inches.
Which of the two synchro designation code is indicated by 5DG on a synchro nameplate?
Navy prestandard code. (3 3/8 to 3 5/8 inch differential transmitter)
On the synchro schematic symbol, what indicates the angular displacement of the rotor?
The position of the arrow. Pointed directly at S2 indicates a zero displacement.
How does the stator receive its voltage from the rotor.
By magnetic coupling.
What are the two common types of synchro rotors?
Salient-pole
Drum or wound
How does the salient-pole differ from the drum/wound visually?
The salient-pole has a single coil wound on a laminated core. The core is shaped like a dumb bell or the letter "H". The drum or wound has coils wound in slots in a laminated core.
How are the salient-pole rotors frequently used?
Used in both transmitters and receivers.
How are the drum/wound rotors frequently used?
In control transformers and differential units and occasionally in torque transmitters.
What are the simularities between the two types of rotors?
Both have coils wound on laminated cores, 2 slip rings mounted on one end of the shaft that is insulated from the shaft to prevent shorting. Both have an insulated terminal board mounted on the end of the cylindrical frame which houses the brushes (provide continuous electrical contact during rotation). the brushes ride on the slip rings. Also mounted on the shaft are low friction ball bearings which permit the rotor to turn easily.
True or false? The rotor and stator turn in all synchros?
False, the stator is usually stationary, but in some synchros both the stator and rotor may be turned. Eletrical connections to this type of stator are made through the slip rings and brushes.
What are the two major components of a synchro?
Rotor and stator
Which of the two main types of rotors can have either a single winding or three Y-connected windings?
Drum/wound
How does the stator receive its voltage?
By magnetic coupling from the rotor
Where are the external connections made on standard synchros?
At the terminal board.
What major factors determine the load capacity of a torque-synchro transmitter?
The number and type of synchro receiver units loating the transmitter, the mechanical loads on these receivers and the operating temperature of these receivers.
Define torque.
A measure of how much load a machine can turn.
What is the unit of measurement in reference to the torque of a synchro transmitter.
Pound-foot or ounce-inch NOT foot pound
What is the operating voltage of most shipboard synchros?
115 volts
What is the operating voltage of most aircraft synchros?
26 volts
At what frequencies are synchros designed to operate?
60 and 400 hertz
At what frequency does synchros operate more efficiently and why?
At the higher frequency, 400 Hz, because the line of flux produced by the 400 Hz excitation voltage are musch more concentrated than those produced by the 60 Hz excitation voltage.
Which frequency is the most widely used in airborne equipment?
400 Hz because synchros can be made smaller for the equipment on the aircraft.
Are 60 Hz and 400 Hz synchros interchangeable and if so, when can they be interchanged?
yes, only the 60 Hz for a 400 Hz and only in an emergency situation only where accuracy is not critical because there is a considerable loss of accuracy. NEVER connect a 400 Hz to a 60 Hz voltage. The reduced impedance results in excessive current flow and the winding quickly burn out.
What type of equipment normally uses 26 V 400 Hz synchros?
Aircraft
How do synchros differ from conventional transformers?
Synchros have one primary winding (the rotor) which may be rotated 360 degreesand three stationary secondary windings (the stator) spaced 120 degrees apart.
Describe the zer-position of a synchro transmitter,
The transmitter is in zero-position when the rotor is aligned with the S2 stator winding.
When is the maximum voltage induced into a stator coil?
When the rotor coil is aligned with the stator coil.
What three factors determine the amplitude of the voltage induced into a stator winding?
The amplitude of the primary voltage, the turns ratio and the angular displacement between the rotor and the stator windings.
What is the difference between the torque receiver and the torque transmitter?
They are electrically identical except the receiver has some form of damping.
What are the two types of damping methods?
Electrical and mechanical
Which damping method is used more frequently?
Electrical
What damping method is used to prevent oscillation in large synchro units?
Mechanical
What two components mae up a simple synchro transmission system?
The synchro transmitter and synchro receiver. TX-TR
What leads in a simple synchro system are connected to the ac power line?
What is the relationship between the transmitter and receiver stator voltages when their rotors are in correspondence?
The voltages are equal and opposed to each other.
What is the name giving to the angle through which a transmitter rotor is mechanically rotated?
Signal
What two receiver leads are reversed to reverse the rotor's direction of rotation?
S1 and S3
What is the most likely problem if the transmitter shaft reads 0 degrees when the receiver shaft indicates 180 degrees?
The rotor leads on either the transmitter or the receiver are reversed.
What components make up the differential synchro system?
TX-TDX-TR or TX-TDX-TX
What is the purpose of using diferential synchros instead of regular synchros?
Differential synchros can handle more signals than regular synchros and also perform addition
and subtraction functions.
What are the two types of differential synchros?
The TDX and the TDR.
Other than their physical differences, what is the major difference between a TDX and a TDR?
Their application: a TDX has one electrical and one mechanical input with an electrical output and the TDR has two electrical inputs and one mechanical output.
What determines whether a differential synchro adds or subtracts?
The way the differential synchro is connected in a system is the deciding factor on whether the unit adds or subtracts its inputs.
What happens when the condition of the TX-TDX-TR system are at electrical zero (all the rotors are at 0 degrees.
The TDX merely passes along the voltages applied to its windings without any change. The TX stator voltage is felt at the TDX rotor and with the system in perfect balance
Assume a 240 degree input was applied to a TX-TDX-TR system, what would the output at the TR be if the TDX rotor is at 0 degrees?
240 degrees:

240 - 0 = 240
How do you subtract a higher value from a lower value of degrees, i.e. 10 degrees - 260 degrees?
You first add 360 degrees to the lower value and subtract directly; 360 + 10 = 370 the
370 - 260 = 110 degrees.
If you hold the TX rotor on 0 degrees and turn the TDX rotor to 120 degrees, what would the output be at the TR rotor?
0 + 360 = 360
360 - 120 = 240
Turn the TX to 75 degrees and the TDX is manually set to 30 degrees, what is the output on the TR rotor?
75 -30 = 45
How is addition accomplished using a TX-TDX-TR system?
By reversing the S1 and S3 leads between the TX and TDX and R1 and R3 leads between the TDX and the TR.
If the TX rotor is at 75 degrees and TDX is set to 0 degrees in a addition system, what is the output?
75 + 0 = 75
If the TX is at 75 degrees and the TDX is 30 degreesin a addition system , what is the output?
75 + 30 = 105
What connections in a TDR system are reversed to set up the system for addition?
The R1 and R3 leads between the TDR rotor and the TX to which it is connected.
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?
Clockwise.
What are the three types of control synchros?
Control transmitter (CX), control transformer (CT), and the control differential transmitter (CDX).
What type of synchro is used in systems requiring large amounts of power and a high degree of accuracy?
A control synchro.
How do the CX and CDX differ from the TX and TDX?
The CX and CDX have higher impedance windings.
What three things prevent a CT rotor from turning when voltages are applied to its stator windings?
The rotor is specially wound, it is never connected to an ac supply, and its output is always applied to a high-impedance load.
When a CT is on electrical zero, what is the elationship between its rotor and the S2 winding?
They are perpendicular to each other.
What is the amplitude and voltage induced into the rotor when the CX is turned 90º while the CT remains on electrical zero?
The voltage is maximum and in phase with the ac excitation voltage to the CX.
What is the name given to the electrical output of a CT?
Error signal.
In a control synchro system, when is the output of the CT reduced to zero?
When the CX and CT rotors are in correspondence.
What is the purpose of the synchro capacitor?
To improve overall synchro system accuracy by reducing stator currents.
A-49. TDXs, CDXs, and Cts.
What type of synchros usually require the use of synchro capacitors?
Magnetizing current.
What type of current is eliminated by synchro capacitors?
They are delta-connected across the stator windings.
How are synchro capacitors connected in a circuit?
To keep the connections as short as possible in order to maintain system.
Why are synchro capacitors placed physically close to differentials transmitters and CTs?
A dual or double-speed synchro system.
What is the name given to the synchro system that transmits data at two different speeds?
Greater accuracy without the loss of self-synchronous operation.
What is the main reason for using a multispeed synchro system instead of a single-speed synchro system?
The gear ratio between the two transmitters.
In a dual-speed synchro system what determines the two specific speeds at which the data will be transmitted?
The gear ratio between the two transmitters.
What type of synchro system is used to transmit very large quantities?
A tri-speed synchro system.
If one of the receivers goes bad the entire unit must be replaced.
What is the purpose of "stickoff voltage"?
It is used in synchro systems to prevent false synchronizations.
What is the reference point for alignment of all synchro units?
Electrical zero.
What is the most accurate method of zeroing a synchro?
The voltmeter method.
What is the purpose of the coarse setting of a synchro?
It ensures the synchro is on 0º, not 180º.
When is a synchro receiver (TR) properly zeroed?
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.
What should a voltmeter read when a TX is set on coarse zero?
Approximately 37 volts.
Why should a synchro be rechecked for zero after it is clamped down?
To ensure that it did not move off zero while it was being clamped.
Q-66. What is the output voltage of a CT when it is set on electrical zero?
Zero or minimum voltage.
Q-67. When you zero a multispeed synchro system which synchro should you zero first?
The coarse synchro.
What method of zeroing a synchro is perhaps the fastest but NOT necessarily the most accurate?
The electrical lock method.
What restrictions are placed on the use of the electrical lock method?
It can be used only if the leads of the synchro are accessible and the rotor is free to turn.
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?
The synchro under test is not on electrical zero.
What should you do with a synchro that has a bad set of bearings?
Replace it.
Name two types of trouble you would expect to find in a newly installed synchro system.
Improper wiring and misalignment.
What type of indicator is usually placed in the stator circuit of a torque synchro system?