PRESENTATIONPRESENTATIONONONProject GuideProject GuideMr. S. K. JhaMr. S. K. JhaPresented ByPresented ByAnkit Srivastava(0809020019)Ankit Srivastava(0809020019)Anurag Tiwari(0809020026)Anurag Tiwari(0809020026)Ashish Verma (0809020031)Ashish Verma (0809020031)Buddha Prakash (0809020034)Buddha Prakash (0809020034)
INTRODUCTION Power instability in developing countries createsthe need for automation of phase selection oralternative sources of power to back-up the utilitysupply . Most industrial and commercial applications aredependent on power supply . If the process of changeover is manual, not onlyconsiderable time is wasted but also the deviceor machine may get damaged from human errorduring the changeover connections, incurringmassive losses.
Digital phase selector that can be installed in residentialand office premises where single-phase equipment areused. When any of the mains phase lines fails, itautomatically selects the available phase line (out of threephase lines or backup lines).
CIRCUIT DESCRIPTIONIt comprises phase (or inverter) sensing,control logic and relay driver sections .The phase-sensing circuitry has R,Y,B andinverter sensing sections, which sense thepresence of R,Y,B and inverter supply,respectively.The control logic circuitry decides thephase priority for one out of four lines .
The order of phase priority is R-phasefollowed by Y-phase , B-phase and thenbackup (inverter )as shown in the truthtable given below .The relay-driver section drives the relayaccording to the signal received from thecontrol logic circuitry .Power supply provides the power to controlthe logic circuit and relay driver sections.
Explanation of control logicThe control logic circuit comprises NOTgate, AND gate, diodes and a few passivecomponents.It is basically a priority encoder and worksaccording to the truth table.If an input variable is at logic ‘0’ it meansthat particular phase (line) is absent in thephase selector .
If an input variable is at logic ‘0’ it meansthat particular phase (line) is absent in thephase selector . if an input variable is at logic ‘1’ thatparticular phase (line) is present in thephase selector.
Circuit Description Figure shows the circuit of the digital phase selector. The R-phaseof AC mains supply is rectified by half-wave rectifier IN4007 (D1).The rectified signal is limited to 9 volts by the zener diode andfiltered by a 10úF capacitor. The 15-kilo-ohm resistor acts as thecurrent limiter. The cathode of the zener diode is connected to pin 1 of optocoupler4N35 through a 1-kilo-ohm resistor. The 1-kilo-ohm resistor acts asthe current limiter for 4N35. Each optocoupler consists of a gallium-arsenide infrared LED and a silicon npn phototransistor. When R-phase is present, the internal infrared LED drives the internalphototransistor of 4N35. Emitter Pin 4 of 4N35 is used for the control logic circuitry. All the line-/phase-sensing circuits are similar as explained above.The control logic circuit is isolated from the phase-sensing circuit byoptocoupler 4N35.
Control Logic Description From the truth table, we can easily arrive at the following Booleanequations: R= R phase_______ Y=R phase. Y phase______________ B= R phase. Y phase. B phase_______ INV. = R phase. Y phase. B phase. Inverter The working of the control logic circuit is as simple as its structure.The presence of any of four phase lines, namely R, Y, B andinverter, makes the corresponding variable high (logic 1). Theglowing of a particular LED, bearing the same name as the outputvariable, will indicate top priority.
Components UsedInverter Circuits (CD4069UBC)The CD4069UB consists of six inverter circuits and is manufactured usingcomplementary MOS (CMOS) to achieve wide power supply operatingrange, low power consumption, high noise immunity, and symmetriccontrolled rise and fall times. Features: Wide supply voltage range: 3.0V to 15V High noise immunity
DIODEThis is a junction Diode. If the positive terminal of the battery is connected tothe p-type material (cathode) and the negative terminal to the N-typematerial (Anode), a large current will flow.If the connections are reversed, a very little current will flow.
RELAYRelay is a common, simple application of electromagnetism. It uses anelectromagnet made from an iron rod wound with hundreds of fine copperwire. When electricity is applied to the wire, the rod becomes magnetic. Amovable contact arm above the rod is then pulled toward the rod until itcloses a switch contact. When the electricity is removed, a small spring pullsthe contract arm away from the rod until it closes a second switch contact.By means of relay, a current circuit can be broken or closed in one circuit asa result of a current in another circuit.
RESISTANCEResistance is the opposition of a material to the current. It is measured in Ohms (W). Allconductors represent a certain amount of resistance, since no conductor is 100% efficient. Tocontrol the electron flow (current) in a predictable manner, we use resistors. Electronic circuitsuse calibrated lumped resistance to control the flow of current. Broadly speaking, resistor can bedivided into two groups viz. fixed & adjustable (variable) resistors. In fixed resistors, the value isfixed & cannot be varied. In variable resistors, the resistance value can be varied by an adjusterknob. It can be divided into (a) Carbon composition (b) Wire wound (c) Special type. The mostcommon type of resistors used in our projects is carbon type. The resistance value is normallyindicated by colour bands. Each resistance has four colours, one of the band on either side willbe gold or silver, this is called fourth band and indicates the tolerance, others three band will givethe value of resistance.COLOURS CODE Black 0 Brown 1 Red 2 Orange 3 Yellow 4 Green 5 Blue 6 Violet 7 Grey 8 White 9
IC ULN 2003The output from the logic control circuit is fed to relaydriver ULN2003 (IC7). IC ULN2003 is a high-voltage,high-current Darlington array containing open-collectorDarlington pairs with common emitters. Each channel israted at 500 mA and can withstand peak current of600mA.The ULN2003 is high voltage, high current Darlingtonarrays each containing seven open collectors Darlingtonpairs with common emitters
Optocoupler In electronics, an opto-isolator, also called an optocoupler,photocoupler, or optical isolator, is "an electronic devicedesigned to transfer electrical signals by utilizing light waves toprovide coupling with electrical isolation between its input andoutput". The main purpose of an opto-isolator is "to prevent highvoltages or rapidly changing voltages on one side of the circuit fromdamaging components or distorting transmissions on the otherside." Commercially available opto-isolators withstand input-to-output voltages up to 10 kV and voltage transients with speeds up to10 kV/μs.
ConclusionThe DIGITAL PHASE SELECTOR is an advancedtechnique which is not only used for automation.It is one of the techniques for the power qualityimprovement.This is a safe mode of change over of phase as it uses ic4N35 optocoupler which is high frequency switch.It does not contain any mechanical contacts and hencelosses are negligible.