SUBMITTED BY,

AJITH E GAKHIL K K

BIBITHA K LJAMSHAD THAYYIL

PRAJITH P

AUTOMATIC PHASE SELECTOR

UMA SYAMKUMAR

PROJECT GUIDE

This consist two partsAutomatic phase changer & analog voltmeterConsists of relay & comparatorChanging the ref: voltage we can control the

min: voltage at the output

INTRODUCTION

BLOCK DIAGRAM

COMPARATOR

Compare voltage applied & ref: voltageBoth the magnitudes are same, output is zero.Sat: voltage is 80% of supply voltageMore +ve at non-inverting terminal output is

at +ve saturationMore +ve at inverting terminal output is at -

ve saturation

COMPARATOR

IC can’t supply large output current.So transistor is required555 timer unusual, coz can be used up to

200mA.PNP Transistor is used.Rb is used to limit the current flowing to the

base of the transistor and prevent it being damaged.

A safe rule is to make the base current Ib about five times larger than the value which should just saturate the transistor.

RELAY SWITCHING CIRCUIT

The transistor's maximum collector current Ic(max) must be greater than the load current Ic.

load current Ic = supply voltage Vs

load resistance RL

RELAY SWITCHING CIRCUIT

CIRCUUIT DIAGRAMAUTOMATIC PHASE CHANGER

 Supply at R phase is down by tfr: X1 to deliver 12V

Rectified by D1C1 is the filter.The voltage at the inverting pin2of the

operational amplifier is taken to the voltage driver circuit of the resistor R1and preset resistor VR1.

Ref: voltage at pin 3 is fixed ,is 5.1V.

WORKING

voltage at the pin2 of the IC1 remains high ,i.e., more than reference voltage5.1V,and it’s out put pin 6 also remains high.

T1 not conducting & relay not energising.de-energized phase ‘R’ supplies power to the

load L1 via normally closed (N/c) contact of the relay RL1.

If supply is below 200V, output goes low, so T1 is conducting & relay is energizing.

WORKING

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, via, phase ‘Y’

and phase ‘B,’ can be explained. Switch S1 is mains power ‘on’/ ’off’ switch.

WORKING

TRUTH TABLE

Simply & easily fabricated.Circuit holds only commonly known IC’s and

components that are readily available.Greater raliability and less maintanance

required.Used for critical loads like medical &

computer installations.

ADVANTAGES

Still automatically flip to the ON phase, if the current phase is turned OFF.

We worked on the circuit first theoretically & studied various aspects of the circuit.

We collected the components and it do on the breadboard.

We found the result.By working it we successfully verified & we

are fully satisfied.

CONCLUSION

www.copernic.comwww.datasheets4u.comwww.efymag.comwww.globalspec.com

REFERENCE