Induction Motor Protection 6y5c4r

A PROJECT REPORT ON

INDUCTION MOTOR PROTECTION

DEPARTMENT OF DIPLOMA IN ELECTRICAL

SHRI K.J. POLYTECHNIC BHARUCH

Submitted By: -

Guided By:-

SHRI K. J. POLYTECHNIC (d to Gujarat technological University)

Department of Diploma in Electrical

CERTIFICATE This is certify that

“………………………………………………………………………….” Of diploma in

electrical has completed their project “INDUCTION MOTOR PROTECTION” Satisfactorily during the Year 2012-13

Date:Signature of guide

Head of Department

________________

________________

Examined By:-

ACKNOWLEDGEMENT This PSP seminar report shall be incomplete if we do not convey our heartfelt gratitude to those people from whom We have got considerable and encouragement during this seminar. Many people have helped, provided direction, technical information and advice at all stages of our seminar and it’s our pleasure to say vote of thanks to all of them. However, with the help of our seminar guide “…………………….” it seems much more interesting to write this thesis than we expected.

Also we are very much thankful for our college SHRI K. J. POLYTECHNIC, which provide us a good study environment & available access to get literature. Besides our friends showed their kindly help & in our thesis. Because of them, living in Bharuch & studying in K.J.polytechnic (Bharuch) is a nice time.

ABSTRACT The project is designed to protect an induction motor from single phasing and over temperature. Providing a protection system is very important in industries, using lot of motors such that production is not hampered owing to failure of any motor. The basic idea for the development of this project is to provide safety to the industrial motor/pump/lift Motor etc. If any of the phases, out of the 3 phases is missing or if the temperature of the motor during operation exceeds the threshold value, motor stops immediately. The system uses a 3-Phase power supply where three single phase transformers are connected to it. If any of the phases is not available the corresponding transformer stops supplying power to the circuit. This leads to one of the four relays getting switched OFF. The main relay which is powered through a set of four relays gets disconnected because of one relay not being powered. Thus the main relay that delivers 3 phase supply to the motor gets disconnected. A thermistor is connected to the motor body to sense the temperature. If the temperature increases then supply to the fourth relay is disconnected. Further the project can be enhanced by using current sensors for over load protection and phase sequence sensor for protecting the motor from applying wrong phase sequence.

CHAPTER NO. 1 INTRODUCTION 1.1 INTRODUCTION 1.2 STATEMENT OF UDP

1.1 INTRODUCTION There are a wide range of a.c. motors and motor characteristics in existence, because of the numerous duties for which they are used. All motors need protection, but fortunately, the more fundamental problems affecting the choice of protection are independent of the type of motor and the type of load to which it is connected. There are some important differences between the protection of induction motors and synchronous motors, and these are fully dealt with in the appropriate section. Motor characteristics must be carefully considered when applying protection; while this may be regarded as stating the obvious, it is emphasized because it applies more to motors than to other items of power system plant. For example, the starting and stalling currents/times must be known when applying overload protection, and furthermore the thermal withstand of the machine under balanced and unbalanced loading must be clearly defined. The conditions for which motor protection is required can be divided into two broad categories: imposed external conditions and internal faults. Table 19.1 provides details of all likely faults that require protection.

A.C. Motor Protection EXTERNAL FAULTS

INTERNAL FAULTS

UNBALANCED SUPPLIES

BEARING FAILURES

UNDERVOLTAGES

WINDING FAULTS

SINGLE PHASING

OVERLOADS

REVERSE PHASE SEQUENCE TABLE 1: CAUSES OF MOTOR FAILURES

1.2 STATEMENT OF UDP The basic idea for the development of the project is to provide safety to the Induction Motor. If any of the phases, out of the 3 phases is missing and also if the temperature of the motor during operation exceeds the prescribed value, the supply to the induction motor is cut off immediately.

CHAPTER NO. 2 PROJECT DESCRIPTION 2.1 CIRCUIT DIAGRAM & ITS WORKING 2.2 OPERATION 2.3BLOCK DIAGRAM 2.4 COMPONENT LIST

2.1 CIRCUIT DIAGRAM & ITS WORKING CIRCUIT DESCRIPTION Three numbers step-down transformers from 230v to 12v are used with their primary connected in star and secondary are individually fed to three bridge rectifiers with filter capacitors C2, C3 & C4 from where the DC voltage is fed to a quad Op-amp used as comparator LP339/LM339 to the respective inverting inputs after ing through potential divider. The noninverting inputs of first three comparators are given pre-settable DC voltage by RV1, RV2 & RV3. Another Op-amp is used to with its inverting input by a pre-settable voltage while its noninverting input is given to a series connected thermistor resistor arrangement across the 5v supply. The output of all the 4 comparators are given to drive Q1, Q2,Q3,Q4 that operate respective relays. Al the common NC s of the relays are connected in series and are fed from a DC supply to another 3 CO relay coil with the other point of that connected to GND. Three diodes D14, D15 & D16 are used respectively from each secondary generated DC and finally filtered by C1. Reason behind this is to ensure un-interrupted DC supply for the circuit operation in the event of failure of any one face. A regulator IC 7805 is used for providing steady voltage reference to RV1, RV2, RV3 & RV4.

WORKING

In normal operations presets RV1, RV2, RV3 & RV4 are so set that the output of the comparators is held low resulting in 4 relays phase1 relay,phase2 relay,phase3 relay, temperature relay number4 all are in deactivated condition so the 12v dc flows through NC s of the those relays to the coil of the 3CO relay forcing it be in active operation so that 3 phase supply is available to the load through the NO of the 3CO relay. The project uses lamps instead of the motor. In the event of failure of any phase the corresponding comparator output goes high that switches ON the respective relay ,the of which opens to discontinue the 12V DC supply to the 3CO relay coil. As the 3 CO relay now is deactivated the 3 phase motor connected in series with the NO s open to stop the motor. Similarly while the temperature goes high on the body of the motor, the mounted thermistor resistance falls to develop logic high for Q4 to operate relay4 & disconnect the DC voltage to the 3CO relay coil. Thus in the process the motor is protected against any phase failure or high body temperature.

2.2 OPERATION

2.3BLOCK DIAGRAM

2.4 COMPONENT LIST 1. TRANSFORMER (230 – 12 V AC) 2. VOLTAGE REGULATOR (LM 7805) 3. RECTIFIER 4. FILTER 5. RELAY 6. ULN 2003 7. OP-AMP LM339 8. THERMISTOR 9. BC547 10. LED 11. 1N4007 12. RESISTOR 13. CAPACITOR

2.4.1 TRANSFORMER Transformers convert AC electricity from one voltage to another with a little loss of power. Step-up transformers increase voltage, step-down transformers reduce voltage. Most power supplies use a step-down transformer to reduce the dangerously high voltage to a safer low voltage.

FIG 2.1: A TYPICAL TRANSFORMER

The input coil is called the primary and the output coil is called the secondary. There is no electrical connection between the two coils; instead they are linked by an alternating magnetic field created in the soft-iron core of the transformer. The two lines in the middle of the circuit symbol represent the core. Transformers waste very little power so the power out is (almost) equal to the power in. Note that as voltage is stepped down and current is stepped up. The ratio of the number of turns on each coil, called the turn’s ratio, determines the ratio of the voltages. A step-down transformer has a large number of turns on its primary (input) coil which is connected to the high voltage mains supply, and a small number of turns on its secondary (output) coil to give a low output voltage. TURNS RATIO = (Vp / Vs) = ( Np / Ns ) Where, Vp = primary (input) voltage. Vs = secondary (output) voltage Np = number of turns on primary coil Ns = number of turns on secondary coil Ip = primary (input) current Is = secondary (output) current.

2.4.2 VOLTAGE REGULATOR 7805 Features • Output Current up to 1A. • Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18, 24V. • Thermal Overload Protection. • Short Circuit Protection. • Output Transistor Safe Operating Area Protection.

Description The LM78XX/LM78XXA series of three-terminal positive regulators are available in the TO-220/D-PAK package and with several fixed output voltages, making them useful in a Wide range of applications. Each type employs internal current limiting, thermal shutdown and safe operating area protection, making it essentially indestructible. If adequate heat sinking is provided, they can deliver over 1A output Current. Although designed primarily as fixed voltage regulators, these devices can be used with external components to obtain adjustable voltages and currents.

2.4.3 RECTIFIER A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), current that flows in only one direction, a process known as rectification. Rectifiers have many uses including as components of power supplies and as detectors of radio signals. Rectifiers may be made of solid state diodes, vacuum tube diodes, mercury arc valves, and other components. The output from the transformer is fed to the rectifier. It converts A.C. into pulsating D.C. The rectifier may be a half wave or a full wave rectifier. In this project, a bridge rectifier is used because of its merits like good stability and full wave rectification. In positive half cycle only two diodes( 1 set of parallel diodes) will conduct, in negative half cycle remaining two diodes will conduct and they will conduct only in forward bias only.

2.4.4 FILTER

Capacitive filter is used in this project. It removes the ripples from the output of rectifier and smoothens the D.C. Output received from this filter is constant until the mains voltage and load is maintained constant. However, if either of the two is varied, D.C. voltage received at this point changes. Therefore a regulator is applied at the output stage. The simple capacitor filter is the most basic type of power supply filter. The use of this filter is very limited. It is sometimes used on extremely high-voltage, low-current power supplies for cathode-ray and similar electron tubes that require very little load current from the supply. This filter is also used in circuits where the power-supply ripple frequency is not critical and can be relatively high. Below figure can show how the capacitor changes and discharges.

2.4.5 RELAY A relay is an electrically operated switch. Many relays use an electromagnet to operate a switching mechanism mechanically, but other operating principles are also used. Relays are used where it is necessary to control a circuit by a low-power signal (with complete electrical isolation between control and controlled circuits), or where several circuits must be controlled by one signal.

FIG: 3CO 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 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.

Relays allow one circuit to switch a second circuit which can be completely separate from the first. For example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit. There is no electrical connection inside the relay between the two circuits; the link is magnetic and mechanical.

The coil of a relay es a relatively large current, typically 30mA for a 12V relay, but it can be as much as 100mA for relays designed to operate from lower voltages. Most ICs (chips) cannot provide this current and a transistor is usually used to amplify the small IC current to the larger value required for the relay coil. The maximum output current for the popular 555 timer IC is 200mA so these devices can supply relay coils directly without amplification.

Relays are usually SPDT or DPDT but they can have many more sets of switch s, for example relays with 4 sets of changeover s are readily available. For further information about switch s and the used to describe them please see the page on switches.

Most relays are designed for PCB mounting but you can solder wires directly to the pins providing you take care to avoid melting the plastic case of the relay.

The supplier's catalogue should show you the relay's connections. The coil will be obvious and it may be connected either way round. Relay coils produce brief high voltage 'spikes' when they are switched off and this can destroy transistors and ICs in the circuit. To prevent damage you must connect a protection diode across the relay coil.

2.4.6 THREE PHASE INDUCTION MOTOR

Three-Phase Induction Motors The three-phase induction motor, also called an asynchronous motor, is the most commonly used type of motor in industrial applications. In particular, the squirrel- cage design is the most widely used electric motor in industrial applications.

Principles of Operation The electrical section of the three-phase induction motor as shown in Figure 3.6.1 consists of the fixed stator or frame, a three-phase winding supplied from the three-phase mains and a turning rotor. There is no electrical connection between the stator and the rotor. The currents in the rotor are induced via the air gap from the stator side. Stator and rotor are made of highly magnetizable core sheet providing low eddy current and hysteresis losses.

FIG 3.6.1: THREE PHASE INDUCTION MOTOR

Stator The stator winding consists of three individual windings which overlap one another and are offset by an electrical angle of 120°. When it is connected to the power supply, the incoming current will first magnetize the stator. This magnetizing current generates a rotary field which turns with synchronous speed ns.

For the smallest pole number of 2p = 2 in a 50 Hz circuit the highest synchronous speed is ns = 3000/min-1.

Rotor The rotor in induction machines with squirrel-cage rotors consists of a slotted cylindrical rotor core sheet package with aluminum bars which are ed at the front by rings to form a closed cage. The rotor of three-phase induction motors sometimes is also referred to as an anchor. The reason for this name is the anchor shape of the rotors used in very early electrical devices. In electrical equipment the anchor's winding would be induced by the magnetic field, whereas the rotor takes this role in three-phase induction motors.

Slip The difference between the synchronous speed ns and the speed n in rated operation is called slip s and is generally expressed in percent. Depending on the size of the machine, in rated operation it is roughly 10 to 3%. Slip is one of the most important characteristics of an induction machine.

2.4.7 LM339 DESCRIPTION

The LM339 consists of four independent precision voltage comparators, with an offset voltage specification as low as 20㎷ max for each comparator, which were designed specifically to operate from a single power supply over a wide range of voltages. Operation from split power supplies is also possible and the low power supply current drain is independent of the magnitude of the power supply voltage.

These comparators also have a unique characteristic in that the input common-mode voltage range includes ground, even though they are operated from a single power supply voltage. The LM339 series was designed to directly interface with TTL and CMOS. When operated from both plus and minus power supplies, the LM339 series will directly interface with MOS logic where their low power drain is a distinct advantage over standard comparators.

2.4.8 THERMISTOR A thermistor is a type of resistor whose resistance varies significantly (more than in standard resistors) with temperature. The word is a portmanteau of thermal and resistor. Thermistors are widely used as inrush current limiters, temperature sensors, self-resetting over current protectors, and self-regulating heating elements. Thermistors differ from resistance temperature detectors (RTD) in that the material used in a thermistor is generally a ceramic or polymer, while RTDs use pure metals. The temperature response is also different; RTDs are useful over larger temperature ranges, while thermistors typically achieve a higher precision within a limited temperature range [usually −90 °C to 130 °C].

2.4.9 BC547 TECHNICAL SPECIFICATIONS:

The BC547 transistor is an NPN Epitaxial Silicon Transistor. The BC547 transistor is a general-purpose transistor in small plastic packages. It is used in general-purpose switching and amplification BC847/BC547 series 45 V, 100 mA NPN general-purpose transistors.

BC 547 TRANSISTOR PINOUTS

We know that the transistor is a "CURRENT" operated device and that a large current (Ic) flows freely through the device between the collector and the emitter terminals. However, this only happens when a small biasing current (Ib) is flowing into the base terminal of the transistor thus allowing the base to act as a sort of current control input. The ratio of these two currents (Ic/Ib) is called the DC Current Gain of the device and is given the symbol of hfe or nowadays Beta, (β). Beta has no units as it is a ratio. Also, the current gain from the emitter to the collector terminal, Ic/Ie, is called Alpha, (α), and is a function of the transistor itself. As the emitter current Ie is the product of a very small base current to a very large collector current the value of this parameter α is very close to unity, and for a typical low-power signal transistor this value ranges from about 0.950 to 0.999.

An NPN Transistor Configuration

2.4.10 IN4007 Diodes are used to convert AC into DC these are used as half wave rectifier or full wave rectifier. Three points must he kept in mind while using any type of diode. 1.Maximum forward current capacity 2.Maximum reverse voltage capacity 3.Maximum forward voltage capacity

Fig: 1N4007 diodes The number and voltage capacity of some of the important diodes available in the market are as follows: 

Diodes of number IN4001, IN4002, IN4003, IN4004, IN4005, IN4006 and IN4007 have

maximum reverse bias voltage capacity of 50V and maximum forward current capacity of 1 Amp. 

Diode of same capacities can be used in place of one another. Besides this diode of more

capacity can be used in place of diode of low capacity but diode of low capacity cannot be used in place of diode of high capacity. For example, in place of IN4002; IN4001 or IN4007 can be used but IN4001 or IN4002 cannot be used in place of IN4007.The diode BY125made by company BEL is equivalent of diode from IN4001 to IN4003. BY 126 is equivalent to diodes IN4004 to 4006 and BY 127 is equivalent to diode IN4007.

Fig:PN Junction diode PN JUNCTION OPERATION Now that you are familiar with P- and N-type materials, how these materials are ed together to form a diode, and the function of the diode, let us continue our discussion with the operation of the PN junction. But before we can understand how the PN junction works, we must first consider current flow in the materials that make up the junction and what happens initially within the junction when these two materials are ed together.

Current Flow in the N-Type Material Conduction in the N-type semiconductor, or crystal, is similar to conduction in a copper wire. That is, with voltage applied across the material, electrons will move through the crystal just as current would flow in a copper wire. This is shown in figure 1-15. The positive potential of the battery will attract the free electrons in the crystal. These electrons will leave the crystal and flow into the positive terminal of the battery. As an electron leaves the crystal, an electron from the negative terminal of the battery will enter the crystal, thus completing the current path. Therefore, the majority current carriers in the N-type material (electrons) are repelled by the negative

side of the battery and move through the crystal toward the positive side of the battery.

Current Flow in the P-Type Material

Current flow through the P-type material is illustrated. Conduction in the P material is by positive holes, instead of negative electrons. A hole moves from the positive terminal of the P material to the negative terminal. Electrons from the external circuit enter the negative terminal of the material and fill holes in the vicinity of this terminal. At the positive terminal, electrons are removed from the covalent bonds, thus creating new holes. This process continues as the steady stream of holes (hole current) moves toward the negative terminal

2.4.11 LED Light Emitting Diodes (LED) have recently become available that are white and bright, so bright that they seriously compete with incandescent lamps in lighting applications. They are still pretty expensive as compared to a GOW lamp but draw much less current and project a fairly well focused beam. The diode in the photo came with a neat little reflector that tends to sharpen the beam a little but doesn't seem to add much to the overall intensity. When run within their ratings, they are more reliable than lamps as well. Red LEDs are now being used in automotive and truck tail lights and in red traffic signal lights. You will be able to detect them because they look like an array of point sources and they go on and off instantly as compared to conventional incandescent lamps.

Fig 4.11(a): circuit symbol

Types of LED’S LEDs are produced in an array of shapes and sizes. The 5 mm cylindrical package is the most common, estimated at 80% of world production. The color of the plastic lens is often the same as the actual color of light emitted, but not always. For instance, purple plastic is often used for infrared LEDs, and most blue devices have clear housings. There are also LEDs in extremely tiny packages, such as those found on blinkers and on cell phone keypads. The main types of LEDs are miniature, high power devices and custom designs such as alphanumeric or multi-color.

Fig 4.11(b) Different types of LED’S

2.4.12 RESISTORS

A resistor is a two-terminal electronic component designed to oppose an electric current by producing a voltage drop between its terminals in proportion to the current, that is, in accordance with Ohm's law: V = IR Resistors are used as part of electrical networks and electronic circuits. They are extremely commonplace in most electronic equipment. Practical resistors can be made of various compounds and films, as well as resistance wire (wire made of a high-resistivity alloy, such as nickel/chrome).

The primary characteristics of resistors are their resistance and the power they can dissipate. Other characteristics include temperature coefficient, noise, and inductance. Less wellknown is critical resistance, the value below which power dissipation limits the maximum permitted current flow, and above which the limit is applied voltage. Critical resistance depends upon the materials constituting the resistor as well as its physical dimensions; it's determined by design. Resistors can be integrated into hybrid and printed circuits, as well as integrated circuits. Size, and position of leads (or terminals) are relevant to equipment designers; resistors must be physically large enough not to overheat when dissipating their power.

VARIABLE RESISTORS Adjustable resistors

A resistor may have one or more fixed tapping points so that the resistance can be changed by moving the connecting wires to different terminals. Some wire wound power resistors have a tapping point that can slide along the resistance element, allowing a larger or smaller part of the resistance to be used. Where continuous adjustment of the resistance value during operation of equipment is required, the sliding resistance tap can be connected to a knob accessible to an operator. Such a device is called a rheostat and has two terminals.

Four-band resistors Four-band identification is the most commonly used color-coding scheme on resistors. It consists of four colored bands that are painted around the body of the resistor. The first two bands encode the first two significant digits of the resistance value, the third is a power-of-ten multiplier or number-of-zeroes, and the fourth is the tolerance accuracy, or acceptable error, of the value. The first three bands are equally spaced along the resistor; the spacing to the fourth band is wider. Sometimes a fifth band identifies the thermal coefficient, but this must be distinguished from the true 5-color system, with 3 significant digits. For example, green-blue-yellow-red is 56×104 Ω = 560 kΩ ± 2%. An easier description can be as followed: the first band, green, has a value of 5 and the second band, blue, has a value of 6, and is counted as 56. The third band, yellow, has a value of 104, which adds four 0's to the

end, creating 560,000 Ω at ±2% tolerance accuracy. 560,000 Ω changes to 560 kΩ ±2% (as a kilo- is 103). Each color corresponds to a certain digit, progressing from darker to lighter colors, as shown in the chart below. Color 1st band 2nd band 3rd band (multiplier) 4th band (tolerance) Temp. Coefficient Black 0

0

×100

Brown 1

1

×101

±1% (F)

100 ppm

Red

2

2

×102

±2% (G)

50 ppm

Orange 3

3

×103

15 ppm

Yellow 4

4

×104

25 ppm

Green 5

5

×105

±0.5% (D)

Blue

6

6

×106

±0.25% (C)

Violet 7

7

×107

±0.1% (B)

Gray

8

8

×108

±0.05% (A)

White 9

9

×109

Gold

×10−1

±5% (J)

Silver

×10−2

±10% (K)

None

±20% (M)

There are many mnemonics for ing these colors.

2.4.13 CAPACITORS A capacitor or condenser is a ive electronic component consisting of a pair of conductors separated by a dielectric. When a voltage potential difference exists between the conductors, an electric field is present in the dielectric. This field stores energy and produces a mechanical force between the plates. The effect is greatest between wide, flat, parallel, narrowly separated conductors.

An ideal capacitor is characterized by a single constant value, capacitance, which is measured in farads. This is the ratio of the electric charge on each conductor to the potential difference between them. In practice, the dielectric between the plates es a small amount of leakage current. The conductors and leads introduce an equivalent series resistance and the dielectric has an electric field strength limit resulting in a breakdown voltage. The properties of capacitors in a circuit may determine the resonant frequency and quality factor of a resonant circuit, power dissipation and operating frequency in a digital logic circuit, energy capacity in a high-power system, and many other important aspects. A capacitor (formerly known as condenser) is a device for storing electric charge. The forms of practical capacitors vary widely, but all contain at least two conductors separated by a

non-conductor. Capacitors used as parts of electrical systems, for example, consist of metal foils separated by a layer of insulating film.

Theory of operation Capacitance

Charge separation in a parallel-plate capacitor causes an internal electric field. A dielectric (orange) reduces the field and increases the capacitance.

A simple demonstration of a parallel-plate capacitor A capacitor consists of two conductors separated by a non-conductive region. The nonconductive region is called the dielectric or sometimes the dielectric medium. In simpler , the dielectric is just an electrical insulator. Examples of dielectric mediums are glass, air, paper, vacuum, and even a semiconductor depletion region chemically identical to the conductors. A capacitor is assumed to be self-contained and isolated, with no net electric charge and no influence from any external electric field. The conductors thus hold equal and opposite charges on their facing surfaces, and the dielectric develops an electric field. In SI units, a capacitance of one farad means that one coulomb of charge on each conductor causes a voltage of one volt across the device.

3.1 PROJECT WORK DONE

NO.

PARTICULARS

MONTH

1.

FINDING THE TITAL OF PROJECT

AUGUST 2012

2.

COLLECTION OF DATA FROM INTERNET

3.

2012

PREPARATION OF INITIAL REPORT WITH PRESENTATION

4.

COLLECT COMPONENT

5.

ANALYSIS OF CIRCUIT DIAGRAM

6.

SEPTEMBER

OCTOBER 2012

PREPARATION OF THE REPORT WITH

NOVEMBER

PRESENTATION

2012

PROJECT OUTLINE 4.1 PROJECT OUTCOMES 4.2 ADVANTAGES & DISADVANTAGES 4.3 APLLICATION 4.4 FUTURE SCOPE

4.1 PROJECT OUTCOMES

NO.

PARTICULARS

MONTH

1.

COLLECT THE COMPONENT FROM MARKET

JAN 2014

2.

DESIGN CIRCUIT

FEB 2014

4.

TESTING OF CIRCUIT ANALYSIS

MARCH 2014

5.

PREPARE FINAL REPORT

MARCH 2014

6.

SUBMISSION

APRIL 2014

4.2.1 ADVANTAGES

LOW COST: Induction machines are very cheap when compared to synchronous and DC motors. This is due to the modest design of induction motor. Therefore, these motors are overwhelmingly preferred for fixed speed applications in industrial applications and for commercial and domestic applications where AC line power can be easily attached. LOW MAINTENANCE COST: Induction motors are maintenance free motors unlike dc motors and synchronous motors. The construction of induction motor is very simple and hence maintenance is also easy, resulting in low maintenance cost. EASE OF OPERATION: Operation of induction motor is very simple because there is no electrical connector to the rotor that supply power and current is induced by the movement of the transformer performs on the rotor due to the low resistance of the rotating coils. Induction motors are self start motors. This can result in reducing the effort needed for maintenance. SPEED VARIATION: The speed variation of induction motor is nearly constant. The speed typically varies only by a few percent going from no load to rated load. HIGH STARTING TORQUE: The staring torque of induction motor is very high which makes motor useful for operations where load is applied before the starting of the motor.3 phase induction motors will have self starting torque unlike synchronous motors. However, singlephase induction motors does not have self starting torque and are made to rotate using some auxiliaries.

DURABILITY: Another major advantage an induction motor is that it is durability. This makes it the ideal machine for many uses. This results the motor to run for many years with no cost and maintenance. All these advantages make induction motor to use in many applications such as industrial, domestic and in many applications.

4.2.2 DISADVANTAGES

4.3 APPLICATION  BP level measured 1. 60 beats per minute <120 beats per minute – Normal heartbeat Rate 2. Heartbeats <60beats per minute – Hypotension 3. Heartbeats >120 beats per minute – Hyper Tension  Use as a stethoscope  Valve damage detected from the sound variations

 All basic diagnosis involves heartbeat count.

4.4 FUTURE SCOPE 

EEG, ECG and other health parameters can also be monitored.



Continuous monitoring and future diagnosis can be performed via the same system

(TELEMEDICINE).



More than a single patient at different places can be monitored using single system.

BIBLIOGRAPHY WEBSITES

.



www.beyondlogic.org



www.wikipedia.org



www.howstuffworks.com



www.alldatasheets.com