1. AUTO SELECTION OF ANY AVAILABLE PHASE,
IN 3 PHASE SUPPLY SYSTEM
Submitted
By

2. Introduction
The basic idea for the development of the project is to provide
supply to the single phase load if any of the phases, out of
the 3 phases misses.
The three transformers are connected to the 3 phases supply
It automatically switch to next phase while one phase is misses.
For monitoring the phase shifting we are using NAND gate
logics.
The relay driver IC to change the load to the next phase through
the contacts those are fed from all the three phases.
At final condition it works on inverter .

3. contents
Introduction
Block diagram
Hardware requirements
Power supply
Gate
Opto isolator
Relay
Relay driver
Schematic diagram
Working of the project
Advantages
Applications
Conclusion

4. Block diagram

5. Hardware requirements
TRANSFORMER (230 – 12 V AC)
VOLTAGE REGULATOR (LM 7805)
FILTER
RELAY
ULN 2003
OPTO ISOLATOR
AND GATE IC 4081
INVERTER IC 4069
LED
1N4007
RESISTOR
CAPACITOR

6. Hardware Components description
1. 230 V AC
50 Hz
12V step down
transformer
2. Using In4007 as Bridge rectifier
3. Capacitors Filter(470µf) 4. 5v Regulator 5. Relay

7. 6. ULN2003 7. OPTO-ISOLATOR
8. AND GATES IC 4081

8. 8. INVERTER IC 4069
9. LED
10. RESISTOR

9. 11. Capacitor
12. 3c/0 relay

10. Power supply
Description of power supply

11. Description of power supply
The circuit uses standard power supply comprising of a step-down
transformer from 230v to 12v and 4 diodes forming a Bridge Rectifier
that delivers pulsating dc which is then filtered by an electrolytic
capacitor of about 470microf to 100microF.
The filtered dc being un regulated IC LM7805 is used to get 5v
constant at its pin no 3 irrespective of input dc varying from 9v to 14v.
The regulated 5volts dc is further filtered by a small electrolytic
capacitor of 10 micro f for any noise so generated by the circuit.
One LED is connected of this 5v point in series with a resistor of
330ohms to the ground i.e. negative voltage to indicate 5v power supply
availability.

12. And Gate discription {Ic 4081}
The 4000 Series CMOS range, and contains four independent
CMOS AND gates each with two inputs.
Pin Description
 Pin 7 is the negative supply
Pin 14 is the positive supply
 Pins 1&2, 5&6, 8&9, 12&13 are gate inputs
 Pins 3, 4, 10, 11 are gate outputs

13. INVERTER IC 4069
The HCC/HCF4069UB consists of six COS/MOS
inverter circuits .
This device is intended for all general purpose inverter
applications where the medium-power TTL-drive and
logic-level-conversion capabilities of circuits such as
HCC/HCF4049B Hex Inverter/Buffers are not
required.
Medium-speed operation- tphl, tplh = 30ns (typ.) A 10v.
quiescent current specified to 20v for hcc device .
standardized symmetrical output characteristics .
5v, 10v, and 15v parametric ratings input current of
100na at 18v and 25°c for hcc device .
100% tested for quiescent current .

14. Opto-isolator
Opto coupler is a 6 pin IC. It is a combination of
1 LED and a transistor
Pin 6 of transistor is not generally used and when
light falls on the Base-Emitter junction then it
switches and pin5 goes to zero.
Relay
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 contacts.
The coil current can be on or off so relays have
two switch positions and have double throw
(changeover) switch contacts as shown in the
diagram.

15. Relay driver uln2003
The ULN2003 is a monolithic high voltage
and high current Darlington transistor arrays.
It consists of seven NPN Darlington pairs that
features high-voltage outputs with common-
cathode clamp diode for switching inductive
loads.
The collector-current rating of a single
Darlington pair is 500mA.
The ULN functions as an inverter.
If the logic at input 1B is high then the output
at its corresponding pin 1C will be low.

16. WORKING
Three phase supply are given to three independent transformers connected
in together with another transformers from receiving supply, an inverter .
The secondary of the transformers are used to develop DC by half wave
rectification and then deriving four number of opto isolators individually.
 The DC supply from all the three phases and inverter supply are combined
and then fed to the regulator IC 7805 for the circuit operation power.
One quad inverter is used in combination with a quad AND the o/p of
which are fed to relay driver IC ULN2003.
The combination of inverter and AND develops a logic of the i/p to the
relay driver IC logic high on the event of any source failure for the next
available supply.
The relays connected drive the load with interlocking logic from the
NO/NC contact such that the 1st phase load automatically changes over to
any available phase in the event of the phase failure.