PRESENTATION PRESENTATION ONON

Project Guide Project Guide Mr. S. K. Jha Mr. S. K. Jha

Presented ByPresented By Ankit 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 creates the need for automation of phase selection or alternative sources of power to back-up the utility supply .

Most industrial and commercial applications are dependent on power supply .

If the process of changeover is manual, not only considerable time is wasted but also the device or machine may get damaged from human error during the changeover connections, incurring massive losses.

Digital phase selector that can be installed in residential and office premises where single-phase equipment are used. When any of the mains phase lines fails, it automatically selects the available phase line (out of three phase lines or backup lines).

CIRCUIT DESCRIPTION

It comprises phase (or inverter) sensing, control logic and relay driver sections .

The phase-sensing circuitry has R,Y,B and inverter sensing sections, which sense the presence of R,Y,B and inverter supply, respectively.

The control logic circuitry decides the phase priority for one out of four lines .

BLOCK DIAGRAM

The order of phase priority is R-phase followed by Y-phase , B-phase and then backup (inverter )as shown in the truth table given below .

The relay-driver section drives the relay according to the signal received from the control logic circuitry .

Power supply provides the power to control the logic circuit and relay driver sections.

TRUTH TABLE

Explanation of control logic

The control logic circuit comprises NOT gate, AND gate, diodes and a few passive components.

It is basically a priority encoder and works according to the truth table.

If an input variable is at logic ‘0’ it means that particular phase (line) is absent in the phase selector .

If an input variable is at logic ‘0’ it means that particular phase (line) is absent in the phase selector .

if an input variable is at logic ‘1’ that particular phase (line) is present in the phase selector.

Circuit Diagram

Circuit Description

Figure shows the circuit of the digital phase selector. The R-phase of AC mains supply is rectified by half-wave rectifier IN4007 (D1). The rectified signal is limited to 9 volts by the zener diode and filtered by a 10úF capacitor. The 15-kilo-ohm resistor acts as the current limiter. 

The cathode of the zener diode is connected to pin 1 of optocoupler 4N35 through a 1-kilo-ohm resistor. The 1-kilo-ohm resistor acts as the 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 internal phototransistor 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 by optocoupler 4N35.

Control Logic Description

From the truth table, we can easily arrive at the following Boolean equations:

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 and inverter, makes the corresponding variable high (logic 1). The glowing of a particular LED, bearing the same name as the output variable, will indicate top priority.

Components Used

Inverter Circuits (CD4069UBC)The CD4069UB consists of six inverter circuits and is manufactured using

complementary MOS (CMOS) to achieve wide power supply operating range, low power consumption, high noise immunity, and symmetric controlled rise and fall times.

Features: Wide supply voltage range: 3.0V to 15V High noise immunity

DIODE

This is a junction Diode. If the positive terminal of the battery is connected to the p-type material (cathode) and the negative terminal to the N-type material (Anode), a large current will flow.

If the connections are reversed, a very little current will flow.

RELAY

Relay is a common, simple application of electromagnetism. It uses an electromagnet made from an iron rod wound with hundreds of fine copper wire. When electricity is applied to the wire, the rod becomes magnetic. A movable contact arm above the rod is then pulled toward the rod until it closes a switch contact. When the electricity is removed, a small spring pulls the 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 as a result of a current in another circuit.

RESISTANCE

Resistance is the opposition of a material to the current. It is measured in Ohms (W). All conductors represent a certain amount of resistance, since no conductor is 100% efficient. To control the electron flow (current) in a predictable manner, we use resistors. Electronic circuits use calibrated lumped resistance to control the flow of current. Broadly speaking, resistor can be divided into two groups viz. fixed & adjustable (variable) resistors. In fixed resistors, the value is fixed & cannot be varied. In variable resistors, the resistance value can be varied by an adjuster knob. It can be divided into (a) Carbon composition (b) Wire wound (c) Special type. The most common type of resistors used in our projects is carbon type. The resistance value is normally indicated by colour bands. Each resistance has four colours, one of the band on either side will be gold or silver, this is called fourth band and indicates the tolerance, others three band will give the 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 2003

The output from the logic control circuit is fed to relay driver ULN2003 (IC7). IC ULN2003 is a high-voltage, high-current Darlington array containing open-collector Darlington pairs with common emitters. Each channel is rated at 500 mA and can withstand peak current of 600mA.

The ULN2003 is high voltage, high current Darlington arrays each containing seven open collectors Darlington pairs with common emitters

Optocoupler

In electronics, an opto-isolator, also called an optocoupler, photocoupler, or optical isolator, is "an electronic device designed to transfer electrical signals by utilizing light waves to provide coupling with electrical isolation between its input and output". The main purpose of an opto-isolator is "to prevent high voltages or rapidly changing voltages on one side of the circuit from damaging components or distorting transmissions on the other side." Commercially available opto-isolators withstand input-to-output voltages up to 10 kV and voltage transients with speeds up to 10 kV/μs.

Conclusion

The DIGITAL PHASE SELECTOR is an advanced technique which is not only used for automation.

It is one of the techniques for the power quality improvement.

This is a safe mode of change over of phase as it uses ic 4N35 optocoupler which is high frequency switch.

It does not contain any mechanical contacts and hence losses are negligible.