CONTENTS

1:- Basic introduction

2:- Basic electrical machines of consideration

3:- Different type of motors

4:- Concept of induction motor

5:- Methods of starting

6:- Methods of speed control

7:- Arrangement of motors at mill 2

9:- IP protection

10:- Electrical insulation

11:- Transformer

12:- DC motor

13:- Circuit breaker

14:- Working of circuit breaker

INTRODUCTION

* WHAT IS CEMENT ?

> A kind of Adhesive.It is a fine pulverized material which is it self is not a binder, but develops the binding property as a result of hydration in presence of water.> In Civil engg. it denotes - a substance which can be used to bind together sand, broken stone or aggregates into a solid mass.Cement is one of the core industries, which plays a vital role in the growth of the nation. India ranks fifth among the cement producing countries in the world and has come a long way, since the installation of the first cement plant at PORBANDER in 1914.India has the requisite quantity of cement grade limestone deposits, backed by adequate reserves of coal.

Cement Manufacturing Process

1:- MININGThe cement manufacturing process starts from the mining of limestone, which is the main raw material of making cement.

2:- CRUSHING, STACKING & RECLAIMING OF LIMESTONEThe lime stone crusher crush the limestone to minus 80mm size & discharge the material into a belt conveyer which takes to the Stacker via the Bulk material analyzer. The material is stack in longitudinal stock piles. The limestone is extracted transversely from the stock piles by Reclaimer and conveyed to the Raw Mill for fine grinding.

3:- CRUSHING, STACKING & RECLAIMING OF COALThe process of making cement clinker requires heat. Coal is used as the fuel for providing heat. Raw coal received from the collieries is stored in a coal yard. Raw coal is crushed in a crusher. Crushed coal discharge from the coal crusher is stored in longitudinal stock piles from where it is reclaimed by reclaimer & taken to Coal Mill for fine grinding.

4:- RAW MILL GRINDING & HOMOGENISATIONReclaimed limestone along with some laterite stored in there respective hoppers is fed to the Raw Mill for fine grinding. The hot gases from the clinker section are used in the Raw Mill for drying and transport of the ground raw meal to the Electro Static Precipitator{ESP} where it is collected & then stored and homogenized in concrete Silo.

5:- CLINKERISATIONRaw meal extracted from Silo now called Kiln feed is fed to preheated for pyroprocessing. Cement clinker is made by Pyroprocessing of kiln feed in Preheater and the rotary kiln.

6:- COOLINGHot clinker discharged from the Kiln drops on the Cooler and gets cooled.

7:- CEMENT GRINDING & STORAGEClinker and Gypsum {for OPC} and also Pozzolana {for PPC} are extracted from their respective hoppers and fed to the cement mills. These cement mills ground the feed to a fine powder. The latter is sent to the cement mill inlet for regrinding and the fine product is stored in concrete silos.

8:- PACKINGCement extracted from silos is conveyed to Automatic Electronic Packers where it is packed in 50kg Polythene Bags and dispatched in trucks.

Fig:- CEMENT MANUFACTURING PROCESS

Packing plant view :- packer

Ash handling

BASIC ELECTRIC MACHINES OF CONSIDERATION

No doubt electricity and electrical machines are the back bone of any productive plant, so far JAYPEE (cement division ) is concerned a number of HT motors , generators, transformers ,circuit breaker are used for operation of the plant.Basically there are two working units in JAYPEE plant Rewa, one with capacity of 25MW and other with 38.5MW. For the generation of this power a captive producing plant is established in the plant with rating 132/6.6 KV. This 132 KV is either generated in the plant or in faulty conditions taken from MPEB.Now for step down this voltage to a level of 6.6KV we use a number of transformers, now this power is sent to the plant where secondary step down is made from 6600/440V. For this purpose only in LC4 we have three heavy transformers, made from CGL

This 440V is sent to control panel and MCC by bus duct, from where it is send to a number of motors and other machines. However it is more clear from the single line diagram shown in the next page. From single line diagram it is quite clear that a number of HT motor and thousands of other small rated motors from 2.7KW to 2650KW are used in LC4.

VIEW FROM LC4

MOTOR :-

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. Unlike the normal transformer which changes the current by using time varying flux, induction motors use rotating magnetic fields to transform the voltage. The current in the primary side creates an electromagnetic field which interacts with the electromagnetic field of the secondary side to produce a resultant torque, thereby transforming the electrical energy into mechanical energy. Induction motors are widely used, especially polyphase induction motors, which are frequently used in industrial drives .

.CLASSFICATION OF MOTOR:-

MOTOR

DC AC SPECIAL

SYNCHRONOUS INDUCTION

1-PHASE 3-PHASE

Squirrel cage slip ring

IN industries mainly three phase induction motor are used due to fact that

Self starting Less armature reaction and brush sparking because of the absence of

commutators . Robust in construction Economical Easier to maintain

5000 KW induction motor at electrical lab

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 into the rotor (usually DC) which in turn creates a (circular uniform) magnetic field around the rotor. The rotating magnetic field of the stator will impose an electromagnetic torque on the still magnetic field of the rotor causing it to move (about a shaft) and rotation of the rotor is produced. 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 polyphase 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 unitless 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.

AC Induction Motor

Where

n = Revolutions per minute (rpm)

f = AC power frequency (hertz)

p = Number of poles per phase (an even number)

Slip is calculated using:

Where s is the slip.

The rotor speed is:

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.

THREE PHASE INDUCTION MOTOR :-

Three phase induction motor is of two type based on construction of rotor

3-Φ induction motor

Squirrel cage slip ring

SQUIRREL CAGE INDUCTION MOTOR:-

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 those solid copper or aluminum strips can be shorted or connected by a ring or sometimes not, i.e. the rotor can be closed or semi closed type. The rotor bars in squirrel-cage induction motors are not straight, but have some skew to reduce noise and harmonics.

ROTOR OF SQUIRREL CAGE MOTOR AT ELECTRICAL LAB 1

STATOR OF SQUIRREL CAGE MOTOR AT ELECTRICAL LAB

ADVANTAGE OF SQUIRREL CAGE MOTOR

Simple and rugged construction No brushes and no slip ring Less maintenance required

SLIP RING INDUCTION MOTOR :-

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

SLIP RING INDUTION MOTOR AT GRINDING MILL

Specification of motor at mill 1Power 2100 kw Current (st) 2323Aspeed 992 rpm Current (rt) 730ADuty S1 Voltage(st) 6600 V ΎIP 23 Voltage(rt) 1780 V ∆Insulation F

ADVANTAGE OF SLIP RING INDUCTION MOTOR

High starting torque Better speed control External resistance can be easily connected through brush and slip

# Why slip ring induction motor extensively not used ?

Slip ring induction motor not used extensively Due to fact that it require

a. high initial cost

b.high maintenance required

both (squirrel cage & silp ring ) work on same principal but they differ in their rotor construction.

# why starting torque of is poor in squirrel cage motor ?

The resistance can not be varied in squirrel cage induction motor as it is possible in slip ring motor .the fix resistance of .the squirrel cage motor is very low .at starting moment induced voltage in rotor has same frequency As the frequency of supply .hence the starting inductive reactance gets higher value at stand still condition .the frequency of rotor of is same as frequency of supply at stand still. Now the case is that the rotor induced current in spite of having higher value lag the induced voltage at large angle so this cause poor starting torque at stand still condition.

REPAIR WORK ON MOTOR

HYDRA MACHINE

squirrel cage motor with gear box

table showing specification of squirrel cage motor :-Power 75 kw Temperature 75 CSpeed 1485 rpm Current (rt) 129 ADuty S1 Voltage (st) 415 VIp 55 Insulation F

STARTING METHOD OF POLYPHASE INDUCTION MOTOR:-

1.SQUIRREL CAGE INDUTION MOTOR

A.FULL VOLTAGE STARTING METHOD

Squirrel Cage motor

Gear box

1. DIRECT ONLINE

panel room 1

since industry have transformers in proximity hence all the squirrel cage motors are direct online started ,otherwise only fractional kilowatt motor are only directly started .

B. REDUCED METHOD STARTING METHOD

1.STATOR RESISTANCE METHOD

2.AUTO TRANSFORMER METHOD

3.STAR DELTA STARTER

2. SLIP RING INDUCTION MOTOR :-

Addition of rotor resistance

in factory LRS ( liquid resistance starter ) is used for starting slip ring motor.

SPEED CONTROL OF MOTOR :-

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. Under load, the speed of the induction motor varies according to size of the load. As the load is increased, the speed of the motor decreases, increasing the slip, which increases the field strength of the rotor to bear the extra load. Before the development of economical semiconductor power electronics, it was difficult to vary the frequency to the motor and induction motors were mainly used in fixed speed applications. As an induction motor has no brushes and is easy to control, many older DC motors are now being replaced with induction motors and accompanying inverters in industrial application.

v/f control no. of stator pole varying supplied voltage adding rheostat

METHOD OF SPEED CONTROL IN INDUSTRIES:-

In industries the speed of slip ring motor is controlled using GRR .

which stand for GRID ROTOR RESISTANCE .

GRID ROTOR RESISTANCE AT MILL 1

POWER & TORQUE EQUATIONS FOR A INDUCTION MACHINE

The input power to a three-phase induction machine is given by

Output power can be found by subtracting the losses from the input powerLosses

1. Stator Copper Loss. The stator resistive losses

2. Rotor Joule Loss. The rotor resistive losses. This is often called rotor copper loss, but since the rotor conductors are aluminum, rotor joule loss is the more correct terminology.

3. Core Loss, or Iron Loss. The losses due to eddy current and hysteresis losses in the laminations. This can be calculated using the resistor Rc. Often, core losses are grouped with friction and windage and stray loss as rotational losses.

Rotor PowerThe power transferred to the rotor is called the "Airgap Power". Consider the equivalent circuit below (the core loss resistance has been removed and core losses grouped into rotational loss).

From the above circuit, it can be seen that the total power transfer to the rotor is given by

To find the power converted to the mechanical system the rotor joule loss must be subtracted from the total rotor power

From the above equations, it can be seen that power converters to the mechanical system is a function of the air gap power and slip:

Final output power may be obtained by subtracting the rotational loss from Pconv.

TorqueAs with all rotating mechanical systems in steady state, torque can be found from the power and mechanical speed

In the case of an induction machine, the electromagnetic torque generated by the machine can be found using

which gives

Writing the torque in terms of the rotor current:

Finally, to find the available shaft torque after rotational losses, the output power must be used.

ARRANGEMENT OF MOTOR AT MILL 2

Arrangement of motor at mil 2 as we can see from above that slip ring HT motors used to drive the grinding mill and squirrel cage LT motor are used in grinding mill .

rotorStatorSlip ring induction motorAt MILL2 (a)

Gear boxShaft for grinding mill

Squirrel cage Motor(b)

Oil circulating pump

the speed of slip ring motor is controlled using grid rotor resistance and that of squirrel cage using variable frequency drive.

In factory mainly motor are air cooled .supply is given to HT motor which have two protection a.overload -relay b.short circuit - fuse

the HT motor also have a differential current transformer (CT) which let you know that fault has occurred .one CT at motor and other at panel any fault occur will disturb the balance condition of current and CT will sense it and will indication will be provided.

gear box 1

DIFFERENT TYPE OF CURRENT TRANSFORMER :-

1.MEASURING CT

2. PROTECTION CT

3. DIFFERTIAL CT

MAINTENACE WORK SLIP RING MOTOR AND CT

MILL 4 MOTOR NAME PLATESPECIFICA. IS325 TEMP RISE 75 CFRAME IRR7716 INSU CLASS FDUTY CONTINOUS CONNECTION STARPOWER 2650 KW AMB.TEM 45 CSPEED 992 STATOR 289 AVOLTAGE(ST) 6600 V ROTOR 910 AVOLTAGE(RT) 1760 V IP 54

Differential current Transformer at Motor side

(slip ring motor)

induction motor (mill 4)

Squirrel cage motors for oil circulationINTERNATION PROTECTION (IP) :-

Ingress Protection (IP) ratings are developed by the European Committee for Electro Technical Standardization (NEMA IEC 60529 Degrees of Protection Provided by Enclosures - IP Code), specifying the environmental protection the enclosure provides.

The IP rating normally has two (or three) numbers:

1. Protection from solid objects or materials2. Protection from liquids (water)3. Protection against mechanical impacts (commonly omitted, the third number is not a part of IEC 60529)Example - IP Rating

With the IP rating IP 54, 5 describes the level of protection from solid objects and 4 describes the level of protection from liquids.

ELECTRICAL INSULATION

Electrical insulation systems are rated by standard NEMA (National Electrical Manufacturers Association) classifications according to maximum allowable operating temperature.

T(oF) = [T(oC)](9/5) + 32

1) Allowable temperature rises are based upon a reference ambient temperature of 40oC. Operation temperature is reference temperature + allowabletemperature rise + allowance for "hot spot" winding.Example Temperature Tolerance Class F:40 oC + 105 oC + 10 oC= 155 oCIn general a motor should not operate with temperatures above the maximum. Each 10 oC rise above the rating may reduce the motor lifetime by one half.It is important to be aware that insulation classes are directly related to motor life.Example - a motor operating at 180oC will have an estimated life ofonly 300 hours with Class A insulation1800 hours with Class B insulation8500 hours with Class F insulation

CLASS TEMPRATUREA 105 C

B 130 CH 155 CF 180 Ctens of thousands of hours with Class H insulationTRANSFORMER:-

TRANSFORMER AND ITS PART

SPECIFICATION OF TRANSFORMER

BUS DUCT

FINS

OIL TANK

BREATHER

NAME PLATE

TEMP RATURECLOCK

KVA 2000 PHASE(P) 3VOLTAGE(P) 6600V CONN. DY11VOLTAGE(S) 433 V FREQUENCY 50HZCURRENT(P) 175A IMPEDENCE V 6.86%CURRENT(S) 2666 A COOLING ONAN

Transformer is electrical machine that :-1.transfer electrical energy from one circuit to another 2.does so without changing frequency 3.by electromagnetic induction4.it is static device because it does not have any moving part

Owing to no moving part it often called “static transformer” and its very rugged machine require minimum amount of repair and maintenanceowing to lack of rotation there is no friction and windage loss.Further other losses are low so that efficiency of transformer is very high.

THERE ARE TWO TYPE OF TRANSFORMER

STEP DOWN STEP UP Step down:- Transformer which input voltage is high and it step down the output voltage . means Input voltage > output voltageSTEP UP :-Transformer in which input voltage is less than output voltage means it it step up the input voltage.

Input voltage < output voltage

NAME PLATE OF TRANSFORMER 1

TESTING OF TRANSFORMER:-

1.MEGGER TEST 2.POLARISATION INDEX TEST 3.SURGE COMPRESSTION TEST 4. HIGH POT TEST

PROTECTION IN TRANSFORMER :-1.BUCHHOLZ RELAY

2.EF RELAY3.DIFFERNTIAL REALY 4.HORN GAP5.LIGHTING ARRESTOR6. OVER FLUX RELAY7.OVER VOLTAGE RELAY 8.OVER CURRENT REALAY9.TEMPRATURE REALY

DIRECT CURRENT MOTOR:-DC motors have a great & very smooth speed control because speed can be controlled by varying field voltage but since the introduction of power drives dc motors are replaced by induction motor .

In the late 1800s, several inventors built the first working motors, which used direct current (DC) power. After the invention of the induction motor, alternating current (AC) machines largely replaced DC machines in most applications. However, DC motors still have many uses.

DC motor principle:- DC motors consist of rotor-mounted windings (armature) and stationary windings (field poles). In all DC motors, except permanent magnet motors, current must be conducted to the armature windings by passing current through carbon brushes that slide over a set of copper surfaces called a commutator, which is mounted on the rotor. The commutator bars are soldered to armature coils. The brush/commutator combination makes a sliding switch that energizes particular portions of the armature, based on the position of the rotor. This

process creates north and south magnetic poles on the rotor that are attracted to or repelled by north and south poles on the stator, which are formed by passing direct current through the field windings. It's this magnetic attraction and repulsion that causes the rotor to rotate.

Figure 3-DC Motor Construction with Feet Integral to Endshields

What is Circuit Breaker?

Definition of circuit breaker : - Electrical circuit breaker is a switching device which can be operated manually as well as automatically for controlling and protection of electrical power system respectively. As the modern power system deals with huge currents, the special attention should be given during designing of circuit breaker to safe interruption of arc produced during the operation of circuit breaker. This was the basic definition of circuit breaker.

Introduction to Circuit Breaker

The modern power system deals with huge power network and huge numbers of associated electrical equipment. During short circuit fault or any other types of electrical fault these equipment as well as the power network suffer a high stress of fault current in them which may damage the equipment and networks permanently. For saving these equipment and the power networks the fault current should be cleared from the system as quickly as possible. Again after the fault is cleared, the system must come to

its normal working condition as soon as possible for supplying reliable quality power to the receiving ends. In addition to that for proper controlling of power system, different switching operations are required to be performed. So for timely disconnecting and reconnecting different parts of power system network for protection and control, there must be some special type of switching devices which can be operated safely under huge current carrying condition. During interruption of huge current, there would be large arcing in between switching contacts, so care should be taken to quench these arcs in circuit breaker in safe manner. The circuit breaker is the special device which does all the required switching operations during current carrying condition.

Working Principle of Circuit Breaker

The circuit breaker mainly consists of fixed contacts and moving contacts. In normal "on" condition of circuit breaker, these two contacts are physically connected to each other due mechanical pressure on the moving contacts. There is an arrangement stored potential energy in the operating mechanism of circuit breaker which is realized if switching signal givent he breaker. The potential energy can be stored in the circuit breaker by different ways like by deforming metal spring, by compressed air, or by hydraulic pressure. But whatever the source of potential energy, it must be released during operation. Release of potential energy makes slidingof the moving contact at extremely fast manner. All circuit breaker have operating coils (trippingcoils and close coil), whenever these coils are energized by switching pulse, the plunger inside them displaced. This operating coil plunger is typically attached to the operating mechanism ofbreaker, as a result the mechanically stored potential energy in the breaker mechanism is in forms of kinetic energy, which makes the moving contact to move as these moving contacts mechanically attached through a gear lever arrangement with the operating mechanism. After a cycle of operation of circuit breaker the total stored energy is released and hence the potential energy again stored in the operating mechanism of circuit breaker by means of spring charging motor or air compressor or by any other means. Till now we have discussed about mechanical working principle of circuit breaker.

But there are electrical characteristics of a circuit breaker which also should be consider in this discussion of operation of circuit breaker.

Let's have a discussion on electrical principle of circuit breaker.

The circuit breaker has to carry large rated or fault power. Due to this large power there is always

dangerously high arcing between moving contacts and fixed contact during operation of circuit breaker. Again as we discussed earlier the arc in circuit breaker can be quenching safely if the dielectric strength between the current carrying contacts of circuit breaker increases rapidly during every current zero crossing of the alternating current. The dielectric strength of the media in between contacts can be increased in numbers of ways, like by compressing the ionized arcing media since compressing accelerates the deionization process of the media, bycooling the arcing media since cooling increase the resistance of arcing path or by replacing the ionized arcing media by fresh gasses. Hence a numbers of arc quenching processes should be involved in operation of circuit breaker.

Types of Circuit Breaker

According different criteria there are different types of circuit breaker.

According to their arc quenching media the circuit breaker can be divided as-

1. Oil circuit breaker.

2. Air circuit breaker.

3. SF6 circuit breaker.

4. Vacuum circuit breaker.