Place of Work:

AA Spinning Mills Ltd Faisalabad

Job TitleVISIT THE FACTORY

This was my first day at Factory. I meet the Electrical Manager. He took my short

interview and the took me to the Electrical Department. He introduced me with

the staff. Then I told them all about me. I was strange for them and they were

strange for me.

Place of Work:

AA Spinning Mills Ltd Faisalabad

Job Title

VISIT THE COMPRESSOR ROOM

I went to the compressor room. This section compressing the air and refrigerant

for the air conditioning purpose in the factory. This section is divided in two parts

because of size of factory. This Section was managed so properly that came very

less time

Safety Precautions

Don’t touch any thing with out permission

Behave good

Place of Work:

AA Spinning Mills Ltd Faisalabad

Job Title

INTRODUCTION TO MOTORS

There are installed induction motors in the factory. These were 3 phase induction

motors. Our Engineer Mr. Zeshan Ali told us about the working of these motors.

The motors works for hole the day without rest, so there were many chances of

fault in the motors.

Safety Precautions

Use right thing for right purpose

Listen to senior carefully

Place of Work:

AA Spinning Mills Ltd Faisalabad

Job Title

FAULTS OF MOTORS (INDUCTION MOTORS)

We came to know about the different faults comes in motors, through our senior.

He told us about short circuit fault. When motor runs with some extra overload,

extra current flows in the winding. Then insulation break down and winding, short

circuit. Then different voices came from the motor. He also guided us about more

faults of motor.

Safety Precautions

Listen to the briefings carefully

Never runs the motor with out extra load

Place of Work:

AA Spinning Mills Ltd Faisalabad

Job Title

TO START INDUCTION MOTOR WITH DOL

This is also called full voltages starting. Direct online starter is installed in series

with supply to start the motor. DOL starter is used to start the motors directly.

One on push and one off push buttons are used to operate DOL starter. An over

load relay operates on overloading of the motor.

Safety Precautions

Use right thing for right purpose

Place of Work:

AA Spinning Mills Ltd Faisalabad

Job Title

REPAIRING A DOL STARTER

A DOL starter circuit is consist of one on push. One off push, one auxiliary for on

push and one contactor. This circuit is installed on two phases ass shown in

figure.

Safety Precautions

Use right thing for right purpose

Be attentive with electricity

Place of Work:

AA Spinning Mills Ltd Faisalabad

Job Title

REPAIRING OVER LOAD FAULT OF INDUCTION MOTOR

Induction motors have the property that they became heated on over boding.

This fault accovrs in on motor. So first of all motor was checked by meters then

load was managed and at last it was started again. When motor becomes over

loaded, over load relay automatically disconnect it from the supply.

Safety Precautions

Use right thing for right purpose

Be conscious with electricity

Place of Work:

AA Spinning Mills Ltd Faisalabad

Job Title

CHECKING OF ELECTROLYTE IN BATTERIES

The electrolyte becomes weak with the passage of time. It has to be refilled after

some time. Specified gravity of fully charged electrolyte should be 1.280 and of

fotaly discharged electrolyte is 1.15 voltages on each cell of lead acid battery are

2.1 volts. We checked all these quantities.

Safety Precautions

Be serious at the time of work with acid.

Place of Work:

AA Spinning Mills Ltd Faisalabad

Job Title

REPAIRING OF FUSE IN BOARD

A fuse was burn out in a board. It has to be changed so I dismentaled it and

changed the fuse wire as per requirement. Then I reinstall it and turn on the

supply. The load of the room was round about 12 to 15 Amp so I used the fuse

wire as its need.

Safety Precautions

Do work safely with Electricity

Place of Work:

AA Spinning Mills Ltd Faisalabad

Job Title

IMPORTANCE OF ELECTRONICS IN INDUSTRIES

Industry work is incomplete without electronics these a days. Electronics has

mad the industry work very reliable. Electronics is playing its role in AA Spinning

mills Ltd also. These are many electronics equipment in the factory. Which are

being used to control and to operate the different sections.

Safety Precautions

Note down all the information

Behave gently

Place of Work:

AA Spinning Mills Ltd Faisalabad

Job Title

INTRODUCTION TO PLC

PLC means programmable logic control. PLC can control different process in

industries. PLC is a device which controls the machinery and its operation with

functions such as logic, timing, counting and scavenging. These functions are

produced in PLC with special processors, which are installed inside the PLC

Safety Precautions

Note down all the information

Be gently

Place of Work:

AA Spinning Mills Ltd Faisalabad

Job Title

ELECTRONIC INSTRUMENTS INSTALLED IN CONTROL ROOM

Electronics instruments were also installed in the control room with along

instruments. These instruments are calibrated with different ratings of electronic

components present inside them. In control room Am meter, V meter, Hz meter

and also an r.p.m meter was installed. Which were working electronically. Taking

reading from these instruments was very easy.

Safety Precautions

Take reading with grate care

Check the batteries of instruments

Place of Work:

AA Spinning Mills Ltd Faisalabad

Job Title

TO KNOW PURPOSE OF RECTIFIER IN CONTROL ROOM

Rectifier is used to convert the AC to Dc in control room F.W.B rectifier used to

supply the battery room for charging purpose and for load safety. Rectifier is a

type of converter.

Safety Precautions

Use diodes as per requirement

Behave gently

Place of Work:

AA Spinning Mills Ltd Faisalabad

Job Title

TWO KNOW THE WORKING OF FILTER IN CONTROL ROOM

Out put of a rectifier is not smooth but it can be converted to smooth state by

using filters. Filters are consist of capacitors and inductors which have the

property of changing pulsating DC to smooth DC

Safety Precautions

Use filter as per requirement

Use right thing for right purpose

Place of Work:

AA Spinning Mills Ltd Faisalabad

Job Title

TO CONTROL THE SPEED OF 3 PHASE INDUCTION MOTOR BY PRIMARY VOLTAGE CONTROL

Means primary resistors the purpose of this method speed control of 3 phase

induction motor is to drop some voltage before giving them to motor. Voltage can

may be reduced by increasing voltage.

Safety Precautions

Use right thing for right purpose

Be serious with electricity

Place of Work:

AA Spinning Mills Ltd Faisalabad

Job Title

REPAIRING THE CIRCUIT BREAKER MOTOR

Description:

Motor in the circuit breaker is used to charge the spring of the circuit breaker.

Spring is used to operate to circuit breaker. And this motor is operated by the

relay. Relay is used to detect the fault from the circuit. And hence the fault will be

detected from the relay and the circuit breaker will disconnect the faulty part of

the circuit from the healthy part.

Reason:

If the motor is charged by the spring. This spring can be broken by any reason

and then the motor will not charge the breaker automatically. Then we have to

charge the breaker with handle charger.

The spring can be broken by friction.

Over hanging of the motor.

Faulty material of the spring.

Dipping on the line.

Fault detecting:

The motor of the breaker will not charge the spring by automatic button.

Compensation:

To compensate this fault change the motor belt or spring of the circuit breaker.

Skill learnt:

How to change the and repair the motor of circuit breaker

Job Title

GENERATORS WORKING AND REPAIRING

Generator Operation

For proper operation of your generator, make sure that it is placed

in an open space. Proper ventilation is vital to its use and your

safety. Also keep the generator dry. The generator should be

placed on a firm, level surface as well.

Don’t forget to run (exercise) your generator at least once a month.

This accomplishes a couple of things. It lubricates the engine by

circulating oil, it runs fresh gas through the carburetor and it works

to recharge the battery. All of these things help to insure that the

generator will start when you really need it in an emergency.

To operate generator

Check the fuel level before starting the generator.

Engines are engineered and designed to run on unleaded

fuel. Use unleaded gasoline with a pump octane rating of 86

or higher. This will reduce deposit build up on valves, spark

arrestor, muffler and spark plugs.

Never use stale or contaminated gasoline or an oil/gas

mixture. Avoid getting dirt or water in the fuel tank.

Be sure to refuel when the engine is off and in a well-

ventilated area. Gasoline is extremely flammable and is

explosive under certain conditions. Do not over fill, and make

sure that any spilled fuel has been wiped off before starting

the generator.

Be sure to refuel when the engine is off and in a well-

ventilated area. Gasoline is extremely flammable and is

explosive under certain conditions. Do not over fill, and make

sure that any spilled fuel has been wiped off before starting

the generator.

The fuel tank cap vents the tank, so be sure to store your

generator in a well-ventilated area. For example, don’t store

the generator below the deck of a boat because gasoline

fumes can collect and ignite.

Check the oil level and air filter.

Make sure the voltage selector is where it needs to be (120v

"only" or 120/240v).

If a 240V appliance is connected to the 4-prong receptacle,

the switch must be in the "120/240V" position (a series

connection). If a 120V appliance ONLY is being connected

to any of the 120V 3-prong receptacles, select the "120V

ONLY" position (for a parallel connection). The benefit of this

is to get maximum power from the 120V 30A locking

receptacle.

Move the generator outside.

Make sure the system is grounded according to local

regulations. See local electrician.

Connect the transfer switch if powering a house.

Connect the power cord to the generator.

Turn the circuit breaker off before starting the generator.

Then allow the generator the warm up before turning the

circuit breaker on.

Check the fuel level

Engines are engineered, designed and certified to run on unleaded fuel. Use

unleaded gasoline with a pump octane rating of 89 or higher. Unleaded fuel will

reduce deposit build-up on valves, spark arrestor, muffler and spark plug(s).

Never use stale or contaminated gasoline or oil/gasoline mixture. Avoid getting

dirt or water in the fuel tank.

Gasoline blended with alcohol or ether is referred to as "oxygenated" fuel. Before

using oxygenated fuel, try to confirm the fuel’s contents (refer to the owner’s

manual). Some states (provinces of Canada) require the information to be posted

on the pump. If you notice any undesirable operating symptoms, try another

service station or switch to another brand of gasoline.

Refuel when the engine is off. Gasoline is extremely flammable and is explosive

under certain conditions. Refuel in a well-ventilated area with the engine stopped.

Do not over fill. Make sure that any spilled fuel has been wiped off before starting

the generator.

The fuel tank cap vents to the atmosphere. Don’t store the generator below the

deck of a boat. Gasoline fumes can collect and ignite. Store the generator in a

well-ventilated area.

Do not smoke or allow sparks in the area when refueling.

Never refuel while the engine/generator is running. Refuel the generator

with the engine stopped and the engine cool.

Wipe up spilled fuel before starting the generator. The engine produces

enough heat at the exhaust system, and the generator produces sufficient

static electricity, to ignite the fuel vapors.

GENERATORS FAULTS AND THEIR ELIMINATION

The red ignition warning light on the combination instrument should light up when the

ignition is switched on and should go out after the engine has started and the engine

speed has begun to rise.

The possible causes of trouble are summarized below:

 Fault  Cause  Remedy

 Warning light does not come on when ignition is switched on

 a. Battery flat  a. Charge up battery

   b. Battery defective  b. Renew battery

   c. Bulb burned out  c. Renew bulb

   d. Battery terminal corroded or loose

 d. Clean connections and if necessary tighten up

   e. Cable loose or broken

 e. Tighten cable or repair

   f. Ignition switch defective

 f. Renew ignition switch

   g. Generator brushes are not running on commutator

 g.Free carbon brushes or renew or replace pressure springs. Do not oil carbon brushes!

 Ignition warning light does not goout when engine speed rises or flickers, glows

 a. V -belt loose or defective

 a. Tighten or renew belt

   b. Regulator switch defective

 b, Exchange regulator switch

   c. Charging lead loose or broken

 c. Check cables and connections

   d. Generator defective

 d. Check generator

   e. Ignition switch lead has bad connection

 e. Tighten connections

 Ignition warning light only goes out at high engine speeds

 a. Generator defective

 a. Check generator, repair

   b. Regulator switch defective

 b. Exchange regulator switch

 Ignition warning light continues to burn after ignition switched off

 a. Short to earth in cable or warning light

 a. Eliminate earth short

DC MOTOR STARTER

The counter-emf aids the armature resistance to limit the current through the

armature. When power is first applied to a motor, the armature does not rotate.

At that instant the counter-emf is zero and the only factor limiting the armature

current is the armature resistance. Usually the armature resistance of a motor is

less than 1 Ω; therefore the current through the armature would be very large

when the power is applied. This current can make an excessive voltage drop

affecting other equipment in the circuit and even trip overload protective devices.

Therefore the need arises for an additional resistance in series with the armature

to limit the current until the motor rotation can build up the counter-emf. As the

motor rotation builds up, the resistance is gradually cut out.

Job Title

TO KNOW USE OF THREE POINT STARTER

The incoming power is indicated as L1 and L2. The components within the

broken lines form the three-point starter. As the name implies there are only

three connections to the starter. The connections to the armature are indicated

as A1 and A2. The ends of the field (excitement) coil are indicated as F1 and F2.

In order to control the speed, a field rheostat is connected in series with the shunt

field. One side of the line is connected to the arm of the starter (represented by

an arrow in the diagram). The arm is spring-loaded so, it will return to the "Off"

position when not held at any other position.

o On the first step of the arm, full line voltage is applied across the shunt

field. Since the field rheostat is normally set to minimum resistance, the

speed of the motor will not be excessive; additionally, the motor will

develop a large starting torque.

o The starter also connects an electromagnet in series with the shunt field. It

will hold the arm in position when the arm makes contact with the magnet.

o Meanwhile that voltage is applied to the shunt field, and the starting

resistance limits the current to the armature.

o As the motor picks up speed counter-emf is built up; the arm is moved

slowly to short.

Safety Precautions

Adjust the value of rheostat with great care.

Note the information.

Job Title

TO KNOW USE OF FOUR-POINT STARTER

The four-point starter eliminates the drawback of the three-point starter. In

addition to the same three points that were in use with the three-point starter, the

other side of the line, L1, is the fourth point brought to the starter when the arm is

moved from the "Off" position. The coil of the holding magnet is connected

across the line. The holding magnet and starting resistors function identical as in

the three-point starter.

The possibility of accidentally opening the field circuit is quite remote. The

four-point starter provides the no-voltage protection to the motor. If the

power fails, the motor is disconnected from the line.

Safety Precautions

Use resistance capacity as per requirement

Be care full with electricity

Note all the information

WHY STARTER IS USED FOR A MOTOR

Starter is used for a motor to limit the high starting current. During starting

of a dc motor high current of up to 4-5 times the full load current occurs

which is avoided by use of high resistance slowly cut out of the circuit.

Starter used to reduce the starting current of the motor. And to safe the

motor winding in the high starting current. Different type of starter used to

the motor. I.e. 3 point starter, 4 point starter used to D.C and A.C motors.

Generally the resistance of armature is very small i.e. in term of .05ohm or

like this. This is due to reduce the losses. If the motor is connected direct

supply high current will flow and it may burn the armature winding. That’s

why starter is connected between supply and motor which reduces the

starting current and provided smooth operation

Starter is basically used to reduce the starting current.

I = (V - Eb) / R.

Where I is the field winding current, V the voltage and Eb - Back up emf

and R the winding resistance. During starting Eb = 0, and R - a very small

resistance. So, as the high current passes through the winding, there is

chance for winding to burn out. When the motor attains the normal speed

it generates the back up emf, enough to reduce the winding current. To

avoid this we need to reduce the voltage (V) or increase the winding

resistance. Since the reduction of supply voltage is difficult to attain, a

starter is used, which will push high resistance during starting and

gradually reduces and fully removed from the circuit when the motor

attains the full speed.

SIMPLE TWO POLE DC MOTOR

The following graphics illustrate a two-pole DC motor.

DC Motor Rotation

A simple DC electric motor. When the coil is powered, a magnetic field is generated around the armature. The left side of the armature is pushed away from the left magnet and drawn toward the right, causing rotation.

The armature continues to rotate.

When the armature becomes horizontally aligned, the commutator reverses the direction of current through the coil, reversing the magnetic field. The process then repeats.

When a current passes through the coil wound around a soft iron core, the side

of the positive pole is acted upon by an upwards force, while the other side is

acted upon by a downward force. According to Fleming's left hand rule, the

forces cause a turning effect on the coil, making it rotate. To make the motor

rotate in a constant direction, "direct current" commutators make the current

reverse in direction every half a cycle (in a two-pole motor) thus causing the

motor to continue to rotate in the same direction.

A problem with the motor shown above is that when the plane of the coil is

parallel to the magnetic field—i.e. when the rotor poles are 90 degrees from the

stator poles—the torque is zero. In the pictures above, this occurs when the core

of the coil is horizontal—the position it is just about to reach in the last picture on

the right. The motor would not be able to start in this position. However, once it

was started, it would continue to rotate through this position by inertia.

There is a second problem with this simple two-pole design. At the zero-torque

position, both commutator brushes are touching (bridging) both commutator

plates, resulting in a short-circuit. The power leads are shorted together through

the commutator plates, and the coil is also short-circuited through both brushes.

(The coil is shorted twice, once through each brush independently.) Note that this

problem is independent of the non-starting problem above; even if there were a

high current in the coil at this position, there would still be zero torque. The

problem here is that this short uselessly consumes power without producing any

motion (or even any coil current). In a low-current battery-powered demonstration

this short-circuiting is generally not considered harmful. (Here, low-current means

that the battery is intrinsically limited to low current and will not overheat if loaded

with a short circuit, this is usually the case for an AA alkaline cell but not the case

for batteries like the Li-ion cells used in many laptop batteries in this first decade

of the 21st century.) However, if a two-pole motor were designed to do actual

work with several hundred watts of power output, this shorting could result in

severe commutator overheating, brush damage, and potential welding of the

brushes—if they were metallic—to the commutator. (Carbon brushes, which are

often used, would not weld.) In any case, a short like this is very wasteful, drains

batteries rapidly, and at a minimum requires power supply components to be

designed to much higher standards than would be needed just to run the motor

without the shorting.

The mechanical power produced by the motor is given by:

As an unloaded DC motor spins, it generates a backwards-flowing electromotive

force that resists the current being applied to the motor. The current through the

motor drops as the rotational speed increases, and a free-spinning motor has

very little current. It is only when a load is applied to the motor that slows the

rotor that the current draw through the motor increases.

THE COMMUTATING PLANE

In a dynamo, a plane through the centers of the contact areas where a pair of

brushes touches the commutator and parallel to the axis of rotation of the

armature is referred to as the commutating plane. In this diagram the

commutating plane is shown for just one of the brushes, assuming the other

brush made contact on the other side of the commutator with radial symmetry,

180 degrees from the brush shown.

DIRECT ON LINE STARTER

A direct on line starter, often abbreviated DOL starter, is a widely-used method

of starting electric motors. The term is used in electrical engineering and

associated with electric motors. There are many types of motor starters, the

simplest of which is the DOL starter. The direct on line starter can be considered

as a switch. When the motor is required to run, the starter supplies the full supply

voltage (such as 400V, 50 Hz, 3-phase in the UK) to the motor. The motor will

start as quickly as it can. A DOL motor starter is distinct from a simple relay in

that it will also contain protection devices, and in some cases, condition

monitoring.

DOL starting is sometimes used to start small water pumps, compressors, fans

and conveyor belts. In the case of an asynchronous motor, such as the 3-Phase

Squirrel-Cage Motor, the motor will pull a high starting current until it has run up

to full speed. This starting current is commonly around 6 times the full load

current, but may as high as 12 times the full load current. For this reason, larger

motors will normally be soft started or run on variable speed drives in order to

minimize disruption to the power supply.

DOL REVERSING STARTER

Most motors are reversible or, in other words, they can be run clockwise and

anti-clockwise. A reversing starter is an electrical or electronic circuit that

reverses the direction of a motor automatically. Logically, the circuit is composed

of two DOL circuits; one for clockwise operation and the other for anti-clockwise

operation. The case of three phase motor inter changing of any two phases will

do the same

SAFETY DEVICE WITHIN THE STARTING CIRCUIT

These devices are used to protect the motor as well as the user of the motor

being operated:

1. Overload Coil The overload coil, also known as a thermal overload, is

designed to open the starting circuit and thus cut the power to the motor in the

event of the motor drawing too much current from the supply. The overload coil is

a normally closed device which opens due to heat generated by excessive

current flowing through the circuit. Thermal overloads have a small heating

device that increases in temperature as the motor running current increases. A

bi-metallic strip located close to the heater deflects as the heater temperature

rises until it mechanically causes the device to trip and open the circuit, cutting

power to the motor should it become overloaded. A thermal overload is basically

a circuit breaker that will accommodate the brief high starting current of a motor

whilst being able to accurately protect it from a running current overload. This is

because the heater coil and the action of the bi-metallic strip introduces a time

delay that affords the motor time to start and settle into normal running current

without the thermal overload tripping. Thermal overloads can be manually or

automatically reset table depending on their application and have an adjuster that

allows them to be accurately set to the motor run current.

2. KM1 No-Volt Coil The No-Volt coil serves the purpose of keeping the holding-

in contactor closed, this is connected in parallel across the start switch (which is

a normally open switch) in the control circuit. The no-volt coil is energized once

the start switch is initiated and keeps current flowing through the control circuit. In

the event of no power being supplied to the motor, the motor will stop. In order

for the motor to be turned on again, the start switch must be initiated and

therefore be the catalyst for closing the holding in contactor and hence energize

the no-volt coil. Only once the no-volt coil is energized, will current remain flowing

in the control circuit

INDUCTION MOTOR

Three-phase induction motors

An induction motor (or asynchronous motor) is a type of alternating current motor where power is supplied to the rotor by means of electromagnetic induction.

An electric motor converts electrical power to mechanical power in its rotor (rotating part). There are several ways to supply power to the rotor. In a DC motor this power is supplied to the armature directly from a DC source, while in an induction motor this power is induced in the rotating device. An induction motor is sometimes called a rotating transformer because the stator (stationary part) is essentially the primary side of the transformer and the rotor (rotating part)

is the secondary side. The primary side's current evokes a magnetic field which interacts with the secondary sides mmf to produce a resultant torque, henceforth serving the purpose of producing mechanical energy. Induction motors are widely used, especially poly phase induction motors, which are frequently used in industrial drives.

Induction motors are now the preferred choice for industrial motors due to their rugged construction, absence of brushes (which are required in most DC motors) and — thanks to modern power electronics — the ability to control the speed of the motor.

PRINCIPLE OF OPERATION AND COMPARISON TO SYNCHRONOUS MOTORS

A 3-phase power supply provides a rotating magnetic field in an induction motor.

The basic difference between an induction motor and a synchronous AC motor is that in the latter a current is supplied onto the rotor. This then creates a magnetic field which, through magnetic interaction, links to the rotating magnetic field in the stator which in turn causes the rotor to turn. It is called synchronous because at steady state the speed of the rotor is the same as the speed of the rotating magnetic field in the stator.

By way of contrast, the induction motor does not have any direct supply onto the rotor; instead, a secondary current is induced in the rotor. To achieve this, stator windings are arranged around the rotor so that when energized with a poly phase supply they create a rotating magnetic field pattern which sweeps past the rotor. This changing magnetic field pattern induces current in the rotor conductors. These currents interact with the rotating magnetic field created by the stator and in effect cause a rotational motion on the rotor.

However, for these currents to be induced, the speed of the physical rotor must be less than the speed of the rotating magnetic field in the stator, or else the magnetic field will not be moving relative to the rotor conductors and no currents will be induced. If by some chance this happens, the rotor typically slows slightly until a current is re-induced and then the rotor continues as before. This difference between the speed of the rotor and speed of the rotating magnetic field in the stator is called slip. It is unit less and is the ratio between the relative speed of the magnetic field as seen by the rotor (the slip speed) to the speed of the rotating stator field. Due to this an induction motor is sometimes referred to as an asynchronous machine.

Formula

The relationship between the supply frequency, f, and the number of poles, p,

and the synchronous speed (speed of rotating field), ns is given by:

From this relationship:

Where

n = Revolutions per minute (rpm)

f = AC power frequency (hertz)

p = Number of poles (an even number)

The rotor speed is:

Where s is the slip.

Slip is calculated using:

A synchronous motor always runs at synchronous speed with 0% slip.

Note on the use of p: Some texts refer to number of pole pairs instead of number

of poles. For example a 6 pole motor would have 3 pole pairs. The equation of

synchronous speed then becomes:

Where p is the number of pole pairs

CONSTRUCTION

The stator consists of wound 'poles' that carry the supply current to induce a magnetic field that penetrates the rotor. In a very simple motor, there would be a single projecting piece of the stator (a salient pole) for each pole, with windings around it; in fact, to optimize the distribution of the magnetic field, the windings

are distributed in many slots located around the stator, but the magnetic field still has the same number of north-south alternations. The number of 'poles' can vary between motor types but the poles are always in pairs (i.e. 2, 4, 6, etc.).

Induction motors are most commonly built to run on single-phase or three-phase power, but two-phase motors also exist. In theory, two-phase and more than three phase induction motors are possible; many single-phase motors having two windings and requiring a capacitor can actually be viewed as two-phase motors, since the capacitor generates a second power phase 90 degrees from the single-phase supply and feeds it to a separate motor winding. Single-phase power is more widely available in residential buildings, but cannot produce a rotating field in the motor (the field merely oscillates back and forth), so single-phase induction motors must incorporate some kind of starting mechanism to produce a rotating field. They would, using the simplified analogy of salient poles, have one salient pole per pole number; a four-pole motor would have four salient poles. Three-phase motors have three salient poles per pole number, so a four-pole motor would have twelve salient poles. This allows the motor to produce a rotating field, allowing the motor to start with no extra equipment and run more efficiently than a similar single-phase motor.

There are three types of rotor:

SQUIRREL-CAGE ROTOR

The most common rotor is a squirrel-cage rotor. It is made up of bars of either solid copper (most common) or aluminum that span the length of the rotor, and are connected through a ring at each end. The rotor bars in squirrel-cage induction motors are not straight, but have some skew to reduce noise and harmonics.

SLIP RING ROTOR

A slip ring rotor replaces the bars of the squirrel-cage rotor with windings that are connected to slip rings. When these slip rings are shorted, the rotor behaves similarly to a squirrel-cage rotor; they can also be connected to resistors to produce a high-resistance rotor circuit, which can be beneficial in starting

SOLID CORE ROTOR

A rotor can be made from a solid mild steel. The induced current causes the rotation.

SPEED CONTROL

The synchronous rotational speed of the rotor (i.e. the theoretical unloaded speed with no slip) is controlled by the number of pole pairs (number of windings in the stator) and by the frequency of the supply voltage. Before the development of cheap power electronics, it was difficult to vary the frequency to the motor and therefore the uses for the induction motor were limited.

The general term for a power electronic device that controls the speed of a motor as well as other parameters is inverter. A typical unit will take the mains AC supply, rectify and smooth it into a "link" DC voltage, and, then convert it into the desired AC waveform. In general, a DC-to-AC converter is called an inverter, which is probably where the motor-control inverter gets its name.

Main article: Variable-frequency driveBecause the induction motor has no brushes and is easy to control, many older DC motors are being replaced with induction motors and accompanying inverters in.

STARTING OF INDUCTION MOTORS

Three Phase

Direct-on-line starting

The simplest way to start a three-phase induction motor is to connect its terminals to the line. This method is often called "direct on line" and abbreviated DOL.

In an induction motor, the magnitude of the induced emf in the rotor circuit is proportional to the stator field and the slip speed (the difference between synchronous and rotor speeds) of the motor, and the rotor current depends on this emf. When the motor is started, the rotor speed is zero. The synchronous speed is constant, based on the frequency of the supplied AC voltage. So the slip speed is equal to the synchronous speed, the slip ratio is 1, and the induced emf in the rotor is large. As a result, a very high current flows through the rotor. This is similar to a transformer with the secondary coil short circuited, which causes the primary coil to draw a high current from the mains.

When an induction motor starts DOL, a very high current is drawn by the stator, in the order of 5 to 9 times the full load current. This high current can, in some motors, damage the windings; in addition, because it causes heavy line voltage drop, other appliances connected to the same line may be affected by the voltage fluctuation. To avoid such effects, several other strategies are employed for starting motors.

Star-delta starters

An induction motor's windings can be connected to a 3-phase AC line in two different ways:

wye (star in Europe), where the windings are connected from phases of the supply to the neutral;

Delta (sometimes mesh in Europe), where the windings are connected between phases of the supply.

A delta connection results in a higher voltage to the windings than a wye connection (the voltage is multiplied by). A star-delta starter initially connects the motor in wye, which produces a lower starting current than delta, then switches to delta when the motor has reached a set speed. Disadvantages of this method over DOL starting are:

Lower starting torque, which may be a serious issue with pumps or any devices with significant breakaway torque

Increased complexity, as more contactors and some sort of speed switch or timers are needed

Two shocks to the motor (one for the initial start and another when the motor switches from wye to delta)

Variable-frequency drives

Variable-frequency drives (VFD) can be of considerable use in starting as well as running motors. A VFD can easily start a motor at a lower frequency than the AC line, as well as a lower voltage, so that the motor starts with full rated torque and with no inrush of current. The rotor circuit's impedance increases with slip frequency, which is equal to supply frequency for a stationary rotor, so running at a lower frequency actually increases torque.

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Autotransformer starters

Such starters are called as auto starters or compensators, consists of an auto-transformer.

SINGLE PHASE

In a single phase induction motor, it is necessary to provide a starting circuit to start rotation of the rotor. If this is not done, rotation may be commenced by manually giving a slight turn to the rotor. The single phase induction motor may rotate in either direction and it is only the starting circuit which determines rotational direction.

For small motors of a few watts the start rotation is done by means of a single turn of heavy copper wire around one corner of the pole. The current induced in the single turn is out of phase with the supply current and so causes an out-of-phase component in the magnetic field, which imparts to the field sufficient rotational character to start the motor. Starting torque is very low and efficiency is also reduced. Such shaded-pole motors are typically used in low-power applications with low or zero starting torque requirements, such as desk fans and record players.

Larger motors are provided with a second stator winding which is fed with an out-

of-phase current to create a rotating magnetic field. The out-of-phase current

may be derived by feeding the winding through a capacitor, or it may derive from

the winding having different values of inductance and resistance from the main

winding.

In some designs the second winding is disconnected once the motor is up to

speed, usually either by means of a switch operated by centrifugal force acting

on weights on the motor shaft, or by a positive temperature coefficient thermistor

which after a few seconds of operation heats up and increases its resistance to a

high value, reducing the current through the second winding to an insignificant

level. Other designs keep the second winding continuously energized during

running, which improves torque.

TYPES OF STARTERS

1. Direct on line starter

2. Autotransformer starter

3. Star Delta starter

4. Resistance starter

5. Fully automatic star delta starter

6. Series reactor starter

WINDING HED ALARM IN AUTO CONE

 

Power Fuse F1 Clear Fault F2Inverter Communication F3 Bobbin change F4Suction Motor Fault F5 Retay Motor Fault F6

Count Fault E0 Key Chain Fault E1Moree Fault E2 CV Fault E3Communication Faults E4 Free E5Clipper Fault E6 Tension Disk Fault E7Spice Fault E8 Bobbin E9

Yearn of Cone is not catch II Bobbin’s yearn II Catch the double yearn from cone II Cutting the yearn H

BLOCK DIAGRAM OF BACK PROCESS (COTTON LINE)

BLOCK DIAGRAM OF BACK PROCESS (POLYISTER LINE)

Place of Work:

AA Spinning Mills Ltd Faisalabad

Job TitleVISIT THE CONTROL ROOM

I went to control room and see its sections. Then Mr. Muhammad Boota told me

that all the sections in factory are being controlled in control room. All the

supplies and other things are being controlled in control room. There were two

persons at the moment in the control room. Attendants came in three shifts in

control room.

Safety Precautions

Don’t touch any thing without permission.

Behave nicely.