Automatic Phase Changer 3e6171

A PROJECT ON AUTOMATIC PHASE CHANGER

SUBMITTED BY :-

1.ABHINAV PANDEY 2.ABHISHEY KUMAR 3.ANUPAM AGRAWAL 4.AWASH AGARWAL

SHAMBHUNATH INSTITUTE OF ENGINEERING & TECHNOLOGY JHALWA , ALLAHABAD 2010-2011

CONTENTS 1. INTRODUCTION 1.1 About project 1.2 Feature 1.2 Components used 2. COMPONENTS USED 2.1 Transformer 2.2 Comparator 2.3 Transistor 2.4 Variable Resistance 2.5 Resistance 2.6 Capacitance 2.7 Zener diode 2.8 Diode 2.9 Relay 2.10 Switches 2.11 Fuse 3. WORKING 3.1 Working of circuit diagram 3.2 Application

ABOUT PROJECT

THIS IS A VERY UNIQUE PROJECT; ARE DEG AN AUTOMATIC PHASE CHANGER

Automation plays a predominant role in the modern scientific world . Automatic phase changer finds application in small offices, residences where single phase equipments are used during phase failure, this unit automatically take the available phase lines and distribute to the non-available phase lines. The circuit is built around a transformer, comparator, transistor & relay. Three identical sets of the circuit, one for each of three phases are used.

IT’S FEATURE • INSTANT AUTOMATIC PHASE CHANGE WHEN ANY PHASE FAILS.

• CAN GET ELECTRIC SUPPLY IN ALL THREE PHASE LINES. • NEED NOT MONITOR FOR SWITCH BACK. • AUTOMATICALLY CHANGES FROM LOW VOLTAGE LINE TO PROPER VOLTAGE LINE. • AVOIDS PHYSICAL OPERATION AND SUFFERING. • CAN SELECT TO SUIT YOUR REQUIREMENT. • QUALITY COMPONENTS ARE USED TO PROVIDE 100% EFFICIENCY.

COMPONENTS USED 1. TRANSFORMER 2. COMPARATOR 3. TRANSISTOR 4. VARIABLE RESISTANCE 5. RESISTANCE 6. CAPACITANCE 7. ZENER DIODE 8. DIODE 9. RELAY 10. SWITCH 11. FUSE

COMPONENTS DETAILS TRANSFORMER DEFINITION:- A TRANSFORMER IS A STATIC PIECE OF APPARATUS BY MEANS OF WHICH ELECTRIC POWER IN ONE CIRCUIT IS TRANSFORMED INTO ELECTRIC POWER OF THE SAME FREQUENCY IN ANOTHER CIRCUIT. THE PHYSICAL BASIS OF A TRANSFORMER IS MUTUAL INDUCTION BETWEEN TWO CIRCUITS LINKED BY A COMMON MAGNETIC FLUX.

COMPARATOR The comparator is a circuit which is used to compare two quantities and provide an output that indicated the relationship between these two quantities. The 741 operational amplifier can be also used as a comparator.

Description • The LM741 series are general purpose operational amplifiers which feature improved performance over industry standards like the LM709. They are direct, plug-in replacements for the 709C, LM201, MC1439 and 748 in most applications. • The amplifiers offer many features which make their application nearly foolproof: overload protection on the input and output, no latch-up when the common mode range is exceeded, as well as freedom from oscillations. • The LM741C is identical to the LM741/LM741A except that the LM741C has their performance guaranteed over a 0°C to +70°C temperature range, instead of -55°C to +125°C.

TRANSISTOR Transistor is a single crystal of silicon (si) or germanium (ge). A transistor can be of two types :- NPN & PNP . A transistor consists of two p-n junction . The junctions are formed by sandwiching either P type or N type semiconductor layers between a pair of opposite types as shown in figure :-

In our circuit we are using PNP transistor ( BC-557) of which description are given below

Description: Transistor. Switching and AF amplifier. High voltage. Low noise. Vcbo = -50V, Vceo= -45V, Vebo = -5V, Pc = 500mW, Ic = -100mA. Pins: 3 Oper. temp.: 0 to 150 Features :1 ) low current ( max . 100 mA) 2 ) low voltage ( max . 65V) Applications :Generally purpose switching & amplifications .

VARIABLE RESISTANCE A potentiometer (colloquially known as a "pot") is a three-terminal resistor with a sliding that forms an adjustable voltage divider. If only two terminals are used (one side and the wiper), it acts as a variable resistor or rheostat. Potentiometers are commonly used to control electrical devices such as volume controls on audio equipment. Potentiometers operated by a mechanism can be used as position transducers, for example, in a joystick.

RESISTANCE Resistor is an electronic device that offers obstruction to the flow of electric current. It can be defined as voltage per unit current through a conductor.

Resistance(R)= Voltage (V) / Current (I) i.e. R=V/I The unit of resistance is ohm denoted by W . The circuit symbol of a resistor is:

HOW TO IDENTIFY THE RESISTANCE VALUE FROM COLOR BANDS Hold the resistor as shown below:

CAPACITANCE In electromagnetism and electronics, capacitance is the ability of a body to hold an electrical charge. Capacitance is also a measure of the amount of electrical energy stored (or separated) for a given electric potential. A common form of energy storage device is a parallel-plate capacitor. In a parallel plate capacitor, capacitance is directly proportional to the surface area of the conductor plates and inversely proportional to the separation distance between the plates. If the charges on the plates are +Q and −Q, and V gives the voltage between the plates, then the capacitance is given by

The SI unit of capacitance is the farad; 1 farad is 1 coulomb per volt.

ZENER DIODE A zener diode is a specially designed junction diode, which can operate continuously without being damaged in the region of reverse breakdown voltage. One of the most important applications of zener diode is the design of constant voltage power supply. The zener diode is ed in reverse bias to d.c. though a resistance R of suitable value.

DIODE The simplest semiconductor device is made of a sandwitch of P-type semiconducting material, with s provided to connect the P-type and n-type layers to an external circuit. This is a junction diode. If the positive terminal of battery is connected to the ptype material (cathode) and the negative terminal to the N-type material (anode), a large current will flow. This called forward current or forward biased.

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. A relay is an electrically operated switch. Current flowing through the coil of the relay creates a magnetic field which attracts a lever and changes the switch s. The coil current can be on or off so relays have two switch positions and most have double throw (changeover) switch s as shown in the diagram.

SWITCH In electronics, a switch is an electrical component that can break an electrical circuit, interrupting the current or diverting it from one conductor to another.The most familiar form of switch is a manually operated electromechanical device with one or more sets of electrical s. Each set of s can be in one of two states: either 'closed' meaning the s are touching and electricity can flow between them, or 'open', meaning the s are separated and nonconducting. A switch may be directly manipulated by a human as a control signal to a system, such as a computer keyboard button, or to control power flow in a circuit, such as a light switch. For example, a thermostat is a temperature-operated switch used to control a heating process. A switch that is operated by another electrical circuit is called a relay.

FUSE In electronics and electrical engineering a fuse (from the Latin "fusus" meaning to melt) is a type of sacrificial overcurrent protection device. Its essential component is a metal wire or strip that melts when too much current flows, which interrupts the circuit in which it is connected. Short circuit, overload or device failure is often the reason for excessive current. A fuse interrupts excessive current (blows) so that further damage by overheating or fire is prevented.

CRICUIT DIAGRAM OF AUTOMATIC PHASE CHANGER

WORKING OF THE CIRCUIT

THE CIRCUIT IS BUILT AROUND A TRANSFORMER, COMPARATOR, TRANSISTOR AND RELAY. THREE IDENTICAL SETS OF THIS CIRCUIT, ONE EACH FOR THREE PHASES, ARE USED. LET US NOW CONSIDER THE WORKING OF THE CIRCUIT CONNECTING RED CABLE (CALL IT ‘R’ PHASE). THE MAINS POWER SUPPLY PHASE R IS STEPPED DOWN BY TRANSFORMER X1 TO DELIVER 12V, 300 MA, WHICH IS RECTIFIED BY DIODE D1 AND FILTERED BY CAPACITOR C1 TO PRODUCE THE OPERATING VOLTAGE FOR THE OPERATIONAL AMPLIFIER (IC1). THE VOLTAGE AT INVERTING PIN 2 OF OPERATIONAL AMPLIFIER IC1 IS TAKEN FROM THE VOLTAGE DIVIDER CIRCUIT OF RESISTOR R1 AND PRESET RESISTOR VR1. VR1 IS USED TO SET THE REFERENCE VOLTAGE ACCORDING TO THE REQUIREMENT.

The reference voltage at non-inverting pin 3 is fixed to 5.1V through zener diode ZD1. Till the supply voltage available in phase R is in the range of 200V-230V, the voltage at inverting pin 2 of IC1 remains high, i.e., more than reference voltage of 5.1V, and its output pin 6 also remains high. As a result, transistor T1 does not conduct, relay RL1 remains de-energised and phase ‘R’ supplies power to load L1 via normally closed (N/C) of relay RL1. As soon as phase-R voltage goes below 200V, the voltage at inverting pin 2 of IC1 goes below reference voltage of 5.1V, and its output goes low. As a result, transistor T1 conducts and relay RL1 energises and load L1 is disconnected from phase ‘R’ and connected to phase ‘Y’ through relay RL2. Similarly, the auto phase-change of the remaining two phases, viz, phase ‘Y’ and phase ‘B,’ can be explained. Switch S1 is mains power ‘on’/’off’ switch. Use relay s of proper rating and fuses should be able to take-on the load when transferred from other phases. While wiring, assembly and installation of the circuit.

APPLICATIONS

1. RESIDENTAL 2. COMMERCIAL OFFICES 3. FACTORIES OPERATING WITH 1 PHASE MACHINERIES 4. HOSPITALS/BANKS 5. INSTITUTIONS