18-10-2012, 05:53 PM
PHASE SEQUENCE DETECTION WITH THREE PHASE CONTROLLED
POWER SUPPLY
PHASE SEQUENCE DETECTION.pdf (Size: 1.05 MB / Downloads: 127)
TECHNICAL DESCRIPTION
In this project main components are IC4013 which consists a dual D- flip flop; IC4017 is basically a decade counter which is used to run the LED‘S in a proper sequence. Now firstly the output of any three phase m/c is fed to the input of this system. Now in the circuit there be a arrangement of two transistor T5 and T6. The out put of the transistor is fed into the IC4013.This IC is basically a dual D-flip flop. The property of D- flip flop is- The output is same as the input, means that if input is 1 than, output is also 1. A mains phase-sequence indicator serves as a hand-tool in checking electrical wiring, especially the wiring of three-phase AC motors. The basic idea of the circuit is that when any (say, Y) of the three phases (RYB), taken as a reference phase, is at negative-going zero voltage, its leading phase (say, R) is positive while its lagging phase (B) is negative, and these states can be easily verified. The circuit comprises two main parts.
AC phase:-
Things start to get complicated when we need to relate two or more AC voltages or currents that are out of step with each other. By ―out of step,‖ I mean that the two waveforms are not synchronized: that their peaks and zero points do not match up at the same points in time. The graph in figure below illustrates an example of this.
PHASE ROTATION:-
The phase angle shift of 120o is a function of the actual rotational angle shift of the three pairs of windings (Figure below). If the magnet is rotating clockwise, winding 3 will generate its peak instantaneous voltage exactly 120o (of alternator shaft rotation) after winding 2, which will hits its peak 120o after winding 1. The magnet passes by each pole pair at different positions in the rotational movement of the shaft. Where we decide to place the windings will dictate the amount of phase shift between the windings' AC voltage waveforms. If we make winding 1 our ―reference‖ voltage source for phase angle (0o), then winding 2 will have a phase angle of -120o (120o lagging, or 240o leading) and winding 3 an angle of -240o (or 120o leading).
ASTABLE MULTIVIBRATOR:-
In the phase sequence and controlled power supply system we use astable multivibrator system, which is used to provide a clock pulse to the pin of the IC 4017. The frequency of the astable multivibrator is unimportant, except that the speed of the LED ring must be visible. If the frequency is high the LED array ring is glowing too fast that we can not find that whether the LED is glowing or not. So the astable multivibrator is very important to slow down the speed of glowing LED array, so that we can easily see the pattern that in what manner the LED is glowing whether in clock wise or in anti clock wise. If the clock wise rotation means that phase are in correct sequence otherwise LED rotate in anti clock wise means that phase are in wrong order.