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The SINGLE PHASING PREVENTER consists of the following blocks

1. POWER CIRCUIT

Basically it consists of step down Transformer, 4 Diodes, Shunt Resistance, Zener

Diode and Filter capacitor. During the positive half cycle of Secondary voltage Vi,

the diodes D2 and D3 are forward biased and conduct the current through load

resistance.

Whereas D1 and D4 are reverse biased and are in off state. It may be observed

that D2, R1 and D3 are in series. During the Negative half cycle of secondary

voltage Vi the current will appears diodes D1, D4 are forward biased and D2, D3

are reversed biased. Therefore the forward biased diode conducts the current

through load resistance. The most important result is that the polarity across the

load resistance R1 is same i.e. current flowing through R1 is same direction.

In this circuit the Zener diode reverse biased p-n junction and operates only in

break down region. Sometimes called as voltage regulator diode because it

maintains a fairly constant output voltage during reverse biased operation.

2. COMPARATOR

An op-amp used as a COMPARATOR. A fixed reference voltage Vref of 1V is

applied to the (pin-3) (-) input and the other varying signal Vin is applied to the

(pin-2) (+) input. Because of this arrangement the circuit is called the non-

inverting Comparator.

When Vin is less than Vref , the output voltage Vo is at +Vsat because the voltage at

the (-) input is higher than that at the (+) input. On the other hand, when Vin is

greater than Vref, the (+) input becomes positive with respect to the (-) input and

Vo goes to +Vsat.

Thus, Vo changes from one saturation level to another. The Comparator is a type

of analog-to-digital converter. At any given time the Vo wave form shows whether

Vin is greater or less than V ref.

SINGLE PHASING PREVENTION OF A 3-Ø IM

3. TRIPPING CIRCUIT

It consists of one n-p-n transistor, diode and relay. The comparator output (pin-6)

is connected to base of BD 115 and collector is connected to voltage source. Relay

and diode are connected in between emitter (BD 115) and ground (-ve) supply.

Transistor BD 115 is used as emitter follower.

In a three phase supply the voltage is 120 degrees apart from each other. Thus the

addition of three phases gives zero voltage. If anyone of the phases goes off

voltage present at the summing point equals half the line voltage.

In this circuit the three phases (R,Y, B) are connected to the line neutral, which in

turn is connected to the ground of the circuit. When all three phases are present,

voltage at point ‘D’ is zero. When phase goes out, voltage at point D goes up to

about half the line voltage. This voltage is divided by 150K and 50K resistors. The

voltage at point B is about 8V when 50K potentiometer is properly adjusted.

The voltage at point 6 is operating condition, so relay will operates when any one

of the phases goes out. This Relay when used in the control circuit of the three

phase motor, or with a circuit breaker will switch the power off on operation.

Figure 1.15: BLOCK DIAGRAM OF SINGLE PHASING PREVENTER


POWER CKT

COMPARATORCKT

TRIPP- ING CKT

STARTER

MOTOR

Xmer P

N D2 D1 D3 D4

D1 TO D4 1N 4007

12.1ZENER

1000mfd 25V

R Y B 150k 150k 150k 150k

D

B BY 127 10K 1K 1K

+ _ 2

4

3

7

6

B

C E

3.8K 50K 32mfd15v

1N 4148

Relay +12V LM741

N

Figure 1.16: CIRCUIT DIAGRAM OF SINGLE PHASING PREVENTER


Figure 1.17: SINGLE LINE DIAGRAM FOR SINGLE PHASING PREVENTER

Future Scope of Single Phasing Preventer


R

B

FUSE

OFF

OLR

SPP

ON HOLDING

CONTACTOR

COIL

LINK

FUSE

In this age of exploding population, the demand for power has increased manifold,

add to that the depleting natural resources of energy. The majority of equipments used

are outdated in this regard. What we want is the Optimum use of energy i.e nothing

should go wasted. The devices & equipments used should be designed to avail a free

flow of energy.

The three-phase induction motors come to use in everyday life, as well as in

industries. The phenomenon of Single Phasing causes a haphazard, the whole of the

system may blow away in seconds, the huge capital invested is gone and we need to

protect our devices & system from any such mishappenings, so the concept of Single

Phasing Preventer comes into the picture. It is not long before its utility was being

questioned, but now it has proved it worth.

Today all the major industries and Distribution Systems of the world are using the

Single Phasing Preventer, its scope is limited, but more efforts being put in its R&D

by the leading economies of the world, including ours would certainly pave its way

into many Naïve sectors which uptill now have not been explored in this case, these

areas include its use along with the Thermal Relays in industries, along with

irrigational pumps in farms, tube wells and many more.

CONCLUSION


The rule of electricity in modern technology is that of an extremely versatile

intermediately. The chief advantage of this energy is that it can be transmitted,

controlled and utilized with relative simplicity, reliability and efficiency.

The primary objective of presenting this project named “DESIGN AND

FABRICATION OF SINGLE PHASE PREVENTER” is to protect the 3-phase

induction motor against single phasing.

This is designed as per our above mentioned requirements. This project states clearly

how it is functioning. In addition to that we discussed about the faults and remedies of

the circuit also.

Every care has been taken to design this project and we expect that this project is very

useful for avoiding single phasing problem for A.C. 3-phase induction motors and

saves the equipment from being damaged.

REFERENCES


i. www.msbte.com

ii. www.ieeexplore.ieee.org

iii. www.areva-td.com

iv. www.power.indiabizclub.com

v. www.protonelectronic.com

vi. www.itee.uq.edu.au

vii. www.progress-energy.com


http://www.itee.uq.edu.au/

http://www.protonelectronic.com/

http://www.areva-td.com/

http://www.msbte.com/

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