Over Voltage and Under Voltage Control Using Relay Essay Sample

8 August 2017

Introduction
The protection system is one O the of import facet on which major makers is concentrating. The companies like L & A ; T. SIMENS etc. The protection system non merely provides lastingness to the equipment but besides avoid jeopardies. The protection system is one of the major Fieldss in the electrical technology. There are different types of protection systems out of that really common and of import 1 is the electromotive force protection system. Normally all the electrical equipments are specified with a specific electromotive force scope for its safe operation. When of all time those equipments are applied with a electromotive force more so the upper specified limit the system may pull extra current which may do to fire the equipment. The equipment is designed to defy a specific electromotive force when of all time the electromotive force goes beyond the bound value so automatically the insularities used in that equipment acquire punctured and do a harm to the equipment.

Similarly whenever the equipment is applied with a electromotive force lower so the lower specified electromotive force it draws extra current to keep the efficiency. The out put may non be proper and the equipment may damage. The complete electromotive force and under electromotive force relay in combination protect the device from fluctuation of electromotive force. This type of relay provides the equipment complete protection against unsought electromotive force status. The complete electromotive force and under electromotive force relay is one of the of import protective relays which is used in the practical application at industries to protect motors transformers and other electronic and electrical equipment and power system.

DESIGN PRINCIPLE:
The complete electromotive force and under electromotive force relay is designed utilizing possible transformers ( PT ) . There is a PT used to try the line electromotive force and converts into DC value. The DC value obtained at the rectifier and filter out put is correspondent to the AC line electromotive force amplitude. The filter is designed with a clip invariable more so five clip period ( 5T ) . The sampling electromotive force obtained at the rectifier filter out put of the PT alterations after 5T merely. In this mode the sampling electromotive force is made immune to the effects of spiks. The sampled electromotive force is feed to two different comparators holding mention electromotive forces correspondent to the under electromotive force and over electromotive force scene. Whenever the sample electromotive force goes beyond the mention electromotive force set for over electromotive force status so comparator end product goes high and a mistake status is detected. Similarly whenever the sample electromotive force goes bellow the mention electromotive force set for under electromotive force status in the other comparator the end product goes high and a mistake status is detected. The end products of both the comparators are feed to a logic gate to bespeak the mistake status when of all time any of the comparator issues a mistake determination. The out put of the logic gate is feed to the bistable / latch and so relay driver and doorbell driver to protect the equipment from the mistake status and bespeak the mistake happening by blowing the doorbell.

CIRCUIT DESCRIPTION
a. Power supply

Circuit connexion: – In this we are utilizing Transformer ( 0-12 ) v. 1Amp. IC 7812. rectifying tubes In 4007. LED & A ; resistances. Here 230V. 50 Hz ac signal is given as input to the primary of the transformer and the secondary of the transformer is given to the span rectification rectifying tube. The o/p of the rectifying tube is given as i/p to the IC regulator ( 7812 ) through capacitance ( 1000mf/35v ) . The o/p of the IC regulator is given to the LED through resistances.

Circuit Explanations: – When ac signal is given to the primary of the transformer. due to the magnetic consequence of the spiral magnetic flux is induced in the spiral ( primary ) and reassign to the secondary spiral of the transformer due to the transformer action. ” Transformer is an electromechanical inactive device which transformer electrical energy from one spiral to another without altering its frequency” . Here the rectifying tubes are connected in a span manner. The secondary spiral of the transformer is given to the span circuit for rectification intents.

During the +ve rhythm of the ac signal the rectifying tubes D2 & A ; D4 behavior due to the forward prejudice of the rectifying tubes and rectifying tubes D1 & A ; D3 does non carry on due to the reversed prejudice of the rectifying tubes. Similarly during the –ve rhythm of the ac signal the rectifying tubes D1 & A ; D3 behavior due to the forward prejudice of the rectifying tubes and the rectifying tubes D2 & A ; D4 does non carry on due to reversed prejudice of the rectifying tubes. The end product of the span rectifier is non a power District of Columbia along with crinkled Ac is besides present. To get the better of this consequence. a capacitance is connected to the o/p of the rectifying tubes ( D2 & A ; D3 ) . Which removes the unwanted ac signal and therefore a pure District of Columbia is obtained. Here we need a fixed electromotive force. that’s for we are utilizing IC regulators ( 7805 & A ; 7812 ) . ”Voltage ordinance is a circuit that supplies a changeless electromotive force regardless of alterations in burden current. ” This IC’s are designed as fixed electromotive force regulators and with equal heat sinking can present end product current in surplus of 1A. The o/p of the span rectifier is given as input to the IC regulator through capacitance with regard to GND and therefore a fixed o/p is obtained. The o/p of the IC regulator ( 7805 & A ; 7812 ) is given to the LED for indicant intent through resistance. Due to the forward prejudice of the LED. the LED freshnesss ON province. and the o/p are obtained from the pin no-3.

B. Under voltage/over electromotive force sensor

In this subdivision our purpose is to observe the line changing electromotive force.

The line electromotive force ( 230vac ) coming from the brinies is to be step down that electromotive force with the aid of a measure down transformer. If the line electromotive force varies. the measure down electromotive force besides varies in conformity with the input electromotive force. Due to the common initiation of the transformer. if the primary twist of the transformer electromotive force is more the flux induced is more and the secondary electromotive force is more. Similarly. if the primary twist of the transformer electromotive force is less the flux induced is less and the secondary electromotive force is less. In this manner under/over electromotive force occurs.

The above figure shows a half-wave rectifier. in which it will change over Ac to dc electromotive force. We can change the electromotive force with the variable burden opposition ( 10k ) The sample electromotive force can be calibrated by changing the burden opposition RL The of import portion of this design to try the electromotive force accurately as an reproduction of the line electromotive force. The measure down transformer samples the line electromotive force at a decreased signal electromotive force Vac = ( N2/N1 ) *VL

The DC electromotive force after the half moving ridge rectifier is about Vm due to the charging of the capacitance. this capacitance electromotive force represents the line electromotive force. The clip invariable of the circuit is defined by C*RL. The clip invariable of the circuit must be more so five times of the clip period of the signal. RC & gt ; 5T. If the RC value is less the 5T so the sample electromotive force fluctuates unnecessarily. if the RC value is excessively high the trying response becomes excessively slow. Operation: The end product of the signal sampling electromotive force ( 3v ) goes to the input of both of the comparator. In the first comparator we have set the electromotive force say 3. 5Vto the non-inverting terminus. In this instance non-inverting terminus is greater than the inverting terminus. That means end product of the first comparator is Low. At present under temperature can ( t be done because the room temperature will be ever available If we want ( s to make under temperature. we have to change or alter the set point which is connected to the inverting terminus of that comparator. Similarly. for the 2nd comparator we have set the electromotive force say 4V to the inverting terminus. In this instance inverting terminus is greater than the non-inverting terminus that means end product of the 2nd comparator is HIGH.

If the temperature increases. the corresponding electromotive force will increase state 4. 5V. That electromotive force goes to the input of both of the comparator. In the first comparator we have set the electromotive force say 3. 5Vto the non-inverting terminus. In this instance inverting terminus is greater than the non- inverting terminus. That means end product of the first comparator is HIGH this means that over temperature has occurred. Similarly. for the 2nd comparator we have set the electromotive force say 4V to the inverting terminus. In this instance non- inverting terminus is greater than the inverting terminus that means end product of the 2nd comparator is LOW.

c. NOR gate
OR Gate
The OR gate is besides called as “any or all” gate. The OR gate is the combinable logic circuit which has merely one end product and may hold any figure of inputs. The end product is when any one or more than one of the input is 1 and the end product is 0 merely when all the input is 0.

In the above figure. a rectifying tube OR gate is shown. It is clear from this circuit if at A +5v input is applied. it will send on colored transistor diode-1 and the end product electromotive force at C will be +5v i. e. . if input A is 1. the end product C will besides be 1 irrespective of input B. likewise. if input to B is 1. the end product at C will besides be 1. irrespective of input to A. the end product C will be 0 merely when both the rectifying tubes are nonconductive i. e. both input are 0 i. e. A=0 and B=0

NOT GATE

Introduction:

The application of the transistors is non limited entirely to the elaboration of the signals. Through proper design transistors can be used as switches for computing machines and control applications. The web of figure-01 ( a ) can be employed as an inverter in computing machine logic circuitry. Note that the end product electromotive force Vc is opposite to the applied to the base or input terminus. In add-on note the absence of dc supply connected to the base circuit. The lone District of Columbia beginning is connected to the aggregator or end product side. and for computing machine applications is typically equal to the magnitude of the “high” side of the applied signal – in this instance 5V.

Operation:

Proper design for the inversion procedure requires that the operating points switch from cut-off to impregnation along the burden line depicted in above figure ( B ) . For our proposes we will presume that IC = ICEO = 0mA. when IB = 0µA ( an first-class estimate in visible radiation of bettering building techniques ) . as shown in above figure ( B ) . In add-on. we will presume that VCE = VCE sat = 0V.

When Vi = 5v. the transistor will be “ON” and design must see that the web is to a great extent saturated by a degree of IB greater than that associated if the IB curve looking near the impregnation degree. In the above figure ( B ) . this requires that IB & gt ; 50µA. The impregnation degree for the aggregator current for the circuit is defined by.

IC = VCC – VCE / RC
= 5V – 0. 2V / 10K
= 480µA

The degree of IB in the active part merely before impregnation consequences can be approximated by the undermentioned equation.

IB min ? IC sat / ?dc
=480µA / 300
=1. 6µA
For the impregnation degree we must therefore insure that the undermentioned status is satisfied: IB max & gt ; IC sat / ?dc
For the web of the above figure ( B ) . when Vi = 5v the ensuing degree of IB is Assume
IB = 100µA
5v – RB IB – 0. 7v = 0
RB ( soap ) = 4. 3 / 100µA = 43k?
RB ( min ) = 4. 3 / IB ( soap ) = 1k?







Which is satisfied. Surely any degree of IB greater than 16µA will go through through a Q- point on the burden line that is really near to the perpendicular axis.

d. Bistable / Latch
Introduction
The latch is the electronics device which shops the province even if the input is with drawn. So this ca be started as a individual memory unit. The latch can be designed in many ways by utilizing a discreet constituent or reversal or a IC known as 555 timer. The Latch designed utilizing 555 timer IC is rather stable. Ckt Connection:

The threshold electromotive force pin-6 of IC555 is connected to land and the trigger pin-2 a pull-up resistance 10k is connected to VCC usually.

Whenever the threshold electromotive force is low. the end product of the comparation-1 hellishly. the end product of the flip-flop goes low. And the input of the comparator – 2 internally high than 1/3 Vcc. the end product will stay in ‘LOW’ sate.

Whenever a negative border trigger electromotive force will look at the trigger pin-2. internally the end product of the comparator – 2 goes high. the reversal will stay in high province and it will latch that end product. Until we have to reset that IC through reset pin-4 to land.

Operation

The 555 timer IC contain two comparators at its input. one terminal of the comparator is connected to the 1/3 Vcc and 2/3 Vcc severally. The other two terminus of both the comparator are named as trigger and threshold. The end product of these two comparators are connected to a S-R somersault –flop in which end product toggles when the inputs are dissimilar i. e. 1. 0 or 0. 1. The Bistable design gas two inputs. one as trigger input to alter the province and the other is to reset the end product. The input signal is connected to the trigger pin and the threshold is grounded. It means the end product of the comparator to which 2/3 Vcc is connected and threshold ( land ) is kept at fixed end product. When the trigger pin is issued with an input which is less than 1/3 Vcc so automatically the comparators end product toggles and therefore the somersault floating-point operation end product toggles and the end product of the 555 timer IC is set. The end product remains in the province until unless the reset input is pulled down to land.

e. Relay driver

In this subdivision we have taken electro magnet relay to command the electrical contraptions we have taken a 12v relay whose opposition is 400? which requires 30mA current to drive or to do it ‘ON’ / ‘OFF’ .

The end product of the reversal is given as input to the relay driver ( as we know. the end product of the reversal is a TTL IC which gives a end product current 50µA. Therefore. we need a driver ckt to drive the relay.

The driver is configured as a transistor acts as a switch. Whenever the base electromotive force is high through a base opposition 1. 5 K and the aggregator is connected to the relay spiral. which as a opposition Rc 400? . the transistor comes to saturation status i. e. ‘ON’ province because the emitter current will flux to the aggregator part. which makes the spiral as electro magnet.

The relay driver is design by utilizing a BC547 transistor. The relay used here holding the specification as follows ? Coil opposition =400ohm
? Coil voltage=12Vdc
? Contact capacity=230V. 7A
The above specification indicates that the spiral requires 12V District of Columbia and 200mA current District of Columbia. The TTL can’t supply more so 20µA current. So driver subdivision is really much required. BC547 has a typical current addition of 200 and maximal current capacity of 1A. So a typical base current of 10 ( A can trip to on the relay. ELECTRO MAGNETIC RELAY


These are really much dependable devices and widely used on field. The operating frequence of these devices are minimal 10-20ms. That is 50Hz – 100Hz. The relay which is used here can care 25mA currents continuously. The electromagnetic relay operates on the rule magnetic attraction. When the base electromotive force appears at the relay driver subdivision. the driver transistor will be driver transistor will be driven into impregnation and let to flux current in the spiral of the relay. Which in bend create a magnetic field and the magnetic force produced due to that will move against the spring tenseness and shut the contact spiral. Whenever the base electromotive force is withdrawn the transistor goes to cutoff. So no current flow in the spiral of the relay. Hence the magnetic field disappears so the contact point interruptions automatically due to spring tenseness. Those contact points are isolated from the low electromotive force supply. so a high electromotive force shift is possible by the aid of electromagnetic relays. The electromagnetic relays usually holding 2 contact points. Named as usually closes ( NC ) . usually unfastened ( NO ) . Normally closed points will so a short CKT way when the relay is away. Normally unfastened points will so a short CKT way when the relay is energized.

f. Buzzer driver

The doorbell driver consists of a doorbell & A ; its driving ckt. It works on the rule of transistor action ( Transistor acts as a switch ) . When the base electromotive force is high. the transistor comes to saturation i. e. in ON status. which drives the doorbell because a little emitter current will flux. Similarly. when the base electromotive force is low. the transistor does non come to saturation i. e. OFF status. which does non drives the doorbell.

Future Expansion
This undertaking is designed with restriction to clip and cost. The complete electromotive force and under electromotive force relay that is designed here can be modified to interface multiple parametric quantities such as temperature and current etc. The interface of micro accountant can do the system more various and smarter. Decision

The complete electromotive force and under electromotive force relay that is designed here in the research lab and tested in the research lab status. And found to be runing satisfactory the set points are set at the restricting value and the practical tripping of the relay is within the bounds of experimental mistakes.

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