Synchronous Data Transmission Systems PDF

I& Intr I o SYNCHRONOUS DATA TRANSMISSION SYSTEM  Angular Position Difference Low Torque / High Torque Device  Introduction to Synchro What is 1.Synchros are...

I& Intr I o SYNCHRONOUS DATA TRANSMISSION SYSTEM  Angular Position Difference Low Torque / High Torque Device  Introduction to Synchro What is 1.Synchros are small low- Synchro? powered electromagnetic devices. 2.Used for the electrical transmission and reception of angular position data or for detection and calculation of the difference between electrical and mechanical information.  The Difference between Synchro and Servo Control System? Synchro Control Systems Servo Control Systems Synchro systems are used A Servo-system is a to transfer feedback control system angular positions or in which motions at least one of the systems in an Open-Loop signals represents Control Chain. mechanical motion.  SYNCHRONOUS DATA TRANSMISSION SYSTEM Objective:  Define the term `synchronous data transmission system’.  Explain the main components and the function of a DC synchronous system.  List the 4 groups of AC synchronous system.  Explain the Principle functions of an AC synchronous system.  State the Principles of operation of:. Torque synchros. Control synchros. Differential synchros. Resolver synchros  Explain the Principle function of a Synchrotel I& SY I DEFINITION OF NC `SYNCHRONOUS DATA TRANSMISSION SYSTEM’ `Synchronous data transmission system’ detects changes in measured quantity and transmit the information electrically to an indicating element. I& SY I NC CLASSES OF SYNCHRONOUS SYSTEM Divided into 2 classes: Direct Current (DC) systems Alternating Current (AC) systems TRANSMIT RECEIVER TER I& SY I NC DIRECT CURRENT SYNCHRONOUS SYSTEM 3 Types of Desynn system Rotary motion (or: Toroidal resistance) for indicating positions and liquid contents. Basic type. Linear motion (or: micro Desynn) for pressure indication Slab Desynn, also for pressure indication I& SY I NC The Basic Synchronous System The main components of Basic Synchronous System consist of: Transmitte Receiver r I& SY I DC Synchronous NC Transmitter Transmitter consists of a resistor wound on a circular former (called the `toroidal resistor’) and is tapped at 120⁰ apart. 2 diametrically- opposed wiper contact arms, one positive and the other negative, are insulated from each other. I& I DC Synchronous SY NC Receiver The receiver consists of: 2-pole permanent magnet rotor. laminated soft- iron star- connected 3- phase stator winding. Receivers are common to all 3 Rotary motion (or: Toroidal types of circuit resistance) arrangement of the for indicating Linear motion positions(or: andmicro liquid Desynn) contents. Basic type. Desynn system. Slab Desynn, for pressure also for indication pressure indication I& SY I Principle of NC Operation Wiper Toroidal arm resistor Wiper 3 Phase boss Star winding 2 Pole Permanent - Circuit diagram of a basic Magnet Desynn system rotor I& SY I Principle Operation of a Basic Desynn NC system 1.When DC is applied, the 3 tapping points in the TX will be at different potentials. 2.These PD causes current to flow through the coils of the receiver stator and produce a magnetic field around A Pull-off magnet’s acts as a power- each coil and failure device to 3. The combined polarised magnetic at differing attract the rotor and field results in total resultant strength. the pointer to an off- magnetic field to create a scale position when torque to align the the current to the permanent-magnet rotor of stator is interrupted. the receiver. Principle of Operation of a Basic Desynn system Torroidal Desynn System Slab Desynn System I& SY I Principle of Operation of a Slab NC Desynn System Errors due to friction can be reduced by providing a good contact material and by burnishing the resistance wire surface. Cyclic Error is reduced by changing the 3 sawtooth waveforms of the basic system into sinusoidal waves. The newly developed transmitter is called Slab Desynn System.  Slab Desynn system Construction. The resistor is wound on a slab former ( ‘slab Desynn’). Supply is DC. The contact arms provide the 3 Potential-tapping points for the indicator stator. Output is tapped from slip ring by Spring-finger brushes to supply the Indicator stator coils. I& SY I NC ALTERNATING CURRENT SYNCHRONOUS SYSTEM Magnesy Autosyn nn n Selsyn n I& SY I NC 4 group of AC synchronous The operation of all these systems are of the same principle. Divided into 4 main groups according to their function: Torque Group 1 synchros Control Group 2 synchros Differential Group 3 synchro Resolver Group 4 synchro I& SY I NC TORQUE SYNCHRO Simplest form of synchro Used to transmit angular position by induced signal which creates a torque, to reproduce positional information at the output element (receiver). Applications; Flight Instrument systems etc. To move light loads, such as positioning of dials, pointers etc. I& SY Rudder Position Torquemet Synchrosco I NC Indicating System er pe Engine Synchrophas Synchronizin Oil Pressure Speed ing g Fuel Flow Dan banyak lagiiiiiii FLAP POSITION AND Float-type Fuel Quantity INDICATING SYSTEM Indicating System I& SY I NC Torque Synchro consists of 2 units TRANSMITT RECEIVER ER (TR) (TX) I& SY I Torque Synchro, NC Transmitter/Receiver Components I& SY I Transmitter and Receiver NC Each consists of a rotor and a stator. Physical differences between the TX and TR is: the rotor of the TX is mechanically coupled to an input shaft, while The rotor the TRwindings rotor is free to units are connected of both to rotate. Single-phase AC. The stator windings are joined together by transmission lines. ROTOR STATOR I& SY I NC Torque Synchro System ROTOR ROTOR Primary Primary Winding Winding STATOR STATOR Secondary Secondary winding winding I& SY I Principle of Operation of a NC Torque Synchro Without power When the rotors are aligned with their respective stators it is said to be at Figure 3 Torque Synchro System `electrical With power applied to the rotors, a certain zero’. voltage will be induced in the stator coils due to transformer action. I& SY I NC Principle of Operation of a Torque Synchro With power applied; When the rotors of TX and TR are in the same angular position, the system is said to be at `NULL When ’. the rotors are in different angular positions, an unbalance (PD) occurs between the stator coil voltages. This PD causes current to flow in the lines and stator coils. Their total resultant magnetic field in the TR exerts torque to turn the TR rotor to the same angular position of the TX rotor. I& SY I NC As the TR rotor continues to turn, the misalignment decreases until the NULL POSITION IS REACHED. No more torque is exerted on the rotor. Angular positional difference between the rotors will be zero. I& SY I NC Synchros in Flight Instrument I& SY I NC CONTROL SYNCHRO Control Synchros differs from Torque Synchros: Control Synchro produce an error voltage signal in the receiving element, but Torque Synchro produces torque at the receiver. Control Synchro systems are used where: large loads need to be moved or produce an `error signal’ of angular position.  CONTROL SYNCHRO Control systems consists of: `Control Transmitter’ CX and `Control Transformer’ CT. Typical applications are in: Servo Altimeters, Airspeed indicators etc (which operate in conjunction with other system e.g. Central Air Data Computers. I& SY I Control synchros consists of 2 NC units Torque Control Synchro Synchro I& SY I Principle Operation of a Control NC Synchro Torque Synchro Similarities/ Difference/s? – AC supply is connected to the CX rotor only. – The CT rotor is a inductive winding for detecting the phase and the magnitude of error signal. – The output voltage is fed to a 2-phase motor via an amplifier. I& SY I Principle Operation of a Control NC Synchro Torque Control Synchro Synchro Another difference is that a Control Synchro System’s `electrical zero’ is when the CT rotor is at 90⁰ with respect to the CX rotor. I& SY I Principle Operation of a Control NC Synchro When the CX rotor is rotated over a certain angle, the resultant flux in the CT stator will be displaced from its datum point by the same angle. Due to displacement of relative position of the CT rotor, an error voltage is induced in the CT I& SY I Principle Operation of a Control NC Synchro The induced error voltage’s phase and magnitude depends on: the direction and The degree of CX rotor displacment.  Principle Operation of a Control Synchro The error voltage is amplified and fed to control the phase of the motor. The phase of the error voltage will determine the speed of motor. I& SY I Principle Operation of a Control NC Synchro As the motor rotates, it turns the rotor of the CT into the appropriate direction and reduces the error voltage i.e. until it reaches its ’electrical I& SY I NC DIFFERENTIAL SYNCHRO Used to detect and transmit error signals representing 2 angular positions to indicate the difference or the sum of the 2 angles/ signals either electrical or electrical and mechanical. This synchro is called as either: Torque Differential Synchro (TDX) or Control Differential Synchro (CDX).  Unlike in TX or CX synchros, the stator and rotor of a differential transmitter are identically wound stator and rotor. When applied in a Differential Synchro system both stator and rotor are interconnected. I& SY I NC RESOLVER SYNCHRO (RS) The function is to convert alternating voltages (cartesian coordinates of a point) into a shaft position and voltage. It represents the polar coordinates of that point. Applications of resolver synchros are in flight directors and integrated I& SY I NC Types of Synchro I& SY I SYNCHROT A synchrotel is used NC as a low-torque EL control transformer or transmitter. Uses 3-phase stator but the rotor section is separated into 3 parts: a hollow, cylindrical rotor made of aluminium a fixed single- phase rotor winding a cylindrical core about which the I& SY I NC SYNCHROTEL In a pressure- measuring application, the synchrotel is electrically connected to a synchro control transmitter whose rotor is made to follow the synchrotel rotor position and acts as a servo loop system. I& SY I SYNCHROTE NC L Rotor (26 V, 400 Hz single-phase), induces voltage into its stator. Alternating flux is established in the stator winding of the Synchrotel. When the Synchrotel rotor is rotated by the sensing element, the flux cutting into the Rotor coil changes. Output of the rotor coil also changes. This induced voltage is fed, via an amplifier, to the control phase of a 2-phase servo motor which drives the Synchro Transmitter. I& SY I NC Typical Application of Synchronous Data Transmission Systems Generally, all the systems described have one common feature: they consist of a transmitter and a receiver which actuates the indicating element (e.g. a pointer). I& SY I NC I& SY I NC Maintenance and Calibration Procedures of Synchros Maintenance Synchros installed in flight instrument systems do not require any maintenance. The synchros of indicators/systems normally require replacement or lubrication only when the unit is removed for repair or complete overhaul. Calibration Adjustment, repair or overhaul of defective synchros may only be performed by qualified personnel (i.e. the manufacturer). I& SY I NC Assignment The END