PROJECT REPORT ONTO STUDY DRIVE FAILURE AND INTERRUPTION IN SCP MACHINES OF BATTERY 567,COKE PLANT AND SUGGEST PRACTICES TO REDUCE INTERRUPTION.

CONTENTTATA STEEL A BRIF INTRODUCTIONINTRODUCTION TO COKE PLANTCOAL CARBONIAZATION OR COKEINGCONVERSION OF COAL TO COKESCHEMATIC DIAGRAM OF COKE PLANTIMPORTANT DIMENSION @ PARAMETERSBATTERY 8@9INTRODUCTION TO DRIVEDRIVECOMPONENT OF DRIVECOMPARISON BETWEEN DC & AC DRIVESIEMENS MASTERDRIVECONCLUSION

TATA STEEL: A Brief Introduction

Established in 1907, Tata Steel is the worlds 6th largest steel company with an existing annual crude steel capacity of 30 million tonnes. Asias first integrated steel plant and Indias largest integrated private sector steel company is now the worlds second most geographically diversified steel producer, with operations in 26 countries and commercial presence in over 50 countries.

Tata Steel completed 100 glorious years of existence on august 26, 2007 following the ideals and philosophy laid down by its founder, Jamshedji Nusserwanji Tata. The first private sector steel plant which started with a production capacity of 1,00,000 tonnes has transformed into a global giant.

Tata Steel plan to grow and globalise through organic and inorganic routes. Its 6.8 million tonnes per annum (MTPA) Jamshedpur Works plan to achieve 10MT capacity by 2010. The Company also has three Greenfield steel projects in the states of Jharkhand, Orissa and Chhattisgarh proposed steel making facilities in Vietnam. Tata Steel is a global player with a balanced presence in developed European and fast growing Asian market and with a strong position in the construction, automotive and packaging markets. Its Jamshedpur steel works produce hot and cold rolled coils and sheets, galvanized sheets, tubes, wire rods, construction rebars, rings and bearings. In an attempt to decommodities steel, the Company has introduced several branded steel products, including Tata Steelium (the worlds first branded Clod Rolled Steel), Tata Shaktee (Galvanised Corrugated Sheets), Tata Tiscon (rebars), Tata Pipes, Tata Bearings, Tata Structura, Tata Agrico (hand tools and implements) and Tata Wiron (galvanized wire products).

In the financial year 2006-07 revenue from the sale of these branded steel products was 26% of the companys sales revenues. Tata Steels vision is to be the global steel industry benchmark for Value Creation and Corporate Citizenship. Tata Steel is one of the few steel companies in the world that is Economic Value Added (EVA) positive. It was ranked the "World's Best Steel Maker", for the third time by World Steel Dynamics in its annual listing in February, 2006. Tata Steel has been conferred the Prime Minister of India's Trophy for the Best Integrated Steel Plant five times.

INTRODUCTION TO COKE PLANT

Coke plant converts naturally found coal into coke, which is suitable for use in the Blast Furnaces. There are six batteries in operation with a total of 284 nos. Stamp Charged ovens And 54 nos. of top charged ovens.

KEY ACTIVITIES OF COKE PLANT

BLENDING COAL PREPARATION STAMPING OF COAL & CAKE MAKING CARBONISATION OF COKE (BATTERY # OPERATION) WHARF MANAGEMENT SIZING OF COKE DESPATCHING OF COKE TO BLAST FURNACE

BLENDING COAL PREPARATION

STAMPING & CHARGING PUSHING

HANDLING OF COKE QUENCHING SYSTEM

WHARF MANAGEMENT SCREENING & SIZING

COKE DESPATCH TO CUSTOMER

COKE PLANTCoke plant is an essential part of an integrated steel plant. Coking process consist of heating of coal (pyrolysis) in absence of air at temperature ranging 9500C to 12000C in oven made up of refractory materials for 20 Hrs. The coal undergoes physical and chemical changes producing volatile chemicals in the form of complex mixture of vapour and gases. At the end of the process a hard porous mass remains, which is coke. Quenching with water-cools the lump coke. The coke is further crushed and screened. During carbonization about 23-25% (by weight) of the initial charges of the coal spews out as mixed gases and vapours, which pass from oven to collecting mains. Byproducts are recovered from these gases and vapours.

COAL CARBONIZATION OR COKING

When coking coal heated in the absence of air they become plastic and soft over a temperature range of 3100C to 5000C. The coal particle agglomerate into a coherent mass, which swells and resolidifies to form a porous structure known as coke.When coal is charged in the hot oven, the temperature of oven refractory wall being at about 11000C to 15000C, the portion of the coal in immediate contact with hot wall is heated very rapidly to a high temperature, a thin layer softens, becomes plastic and melts. This layer of plastic material travels towards the centre of the oven and some of the gaseous product force their way out of the plastic materials, as the temperature of the charge is raised. On the wall side, the plastic layer hardens into a cellar residue and the volatile matter left in the coke is driven of gradually as the temperature rises during remainder of the coke period. Thus in an oven, during initial stage of coking, the coal exists side by side in several phases, e.g. coke, semicoke, a plastic mass and granular coal.

Schematic Diagram of COKE Plant

Oven:Length 13760 mmHeight 4570 mmAverage Width 460 mm (Ram side 450 mm, Middle 460 mm, Coke side 470 mm)Oven Taper 20 mm (From Ram side to Oven side) Oven to Oven Centre Distance 1200 mm Heating chamber:Length 13760 mmHeight 4570 mmAverage Width 740 mm (Ram side 750 mm, Middle 740 mm, Coke side 730 mm) Thickness of Stretcher Wall 95 mm (5 mm more that old Batteries)

IMPORTANT DIMENSIONS AND PARAMETERS

The Battery 8 and 9 of the TATA STEEL is the state of the art battery with worlds best technology achieving the quality parameters of the world class coke as well as meeting 100% of the environmental norms. These are OTTO DESIGN, Stamp Charge battery with 70 ovens in each battery. Its heating system is twin flue, under jet firing type, double stage air, and compound ovens. It can be operated in B.F. (Blast Furnace) Gas or C.O. (Coke Oven) Gas according to requirement. So it is called compound ovens. The capacity of both the batteries combined is one million tons per annum.

BATTERY 8 AND 9

*POWER DISTRIBUTION IN SCP M/CMain Transformer6.6 KV/ 433 V General MCC-1General MCC-2StampingMCCMaster Drive-1MasterDrive-2From HT breaker* SEPARATE BREAKER FOR MASTER DRIVES IN GNL. MCC-1

*MAIN TRANSFORMER (SPEC.) 1OOO KVA, Dry Type Resin cast Transformer.6.6Kv/433, 433v, Dyn5, yn5Secondary current 666.7, 666.7Amps.HT side Amps= 87.5Make: Kirloskar

TITLE OF THE PROJECTTO STUDY DRIVE FAILURE AND INTERRUPTION IN SCP MACHINES OF BATTERY 567,COKE PLANT AND SUGGEST PRACTICES TO REDUCE INTERRUPTION.

INTRODUCTION TO DRIVEDrives are employed for systems that require motion control e.g. transportation system, fans,robots, pumps, machine tools, etc. Prime movers are required in drive systems to provide themovement or motion and energy that is used to provide the motion can come from varioussources: diesel engines, petrol engines, hydraulic motors, electric motors etc.Drives that use electric motors as the prime movers are known as electrical drives There are several advantages of electrical drives: a. Flexible control characteristic This is particularly true when power electronic converters are employed where the dynamic and steady state characteristics of the motorcan be controlled by controlling the applied voltage or current. b. Available in wide range of speed, torque and power c. High efficiency, lower noise, low maintenance requirements and cleaner operation d. Electric energy is easy to be transported.

DRIVE

AC drives, inverters, and adjustable frequency drives are all terms that are used to refer to equipment designed to control the speed of an AC motor. The term SIMOVERT is used by Siemens to identify a SIemens MOtor inVERTer (AC drive).AC drives receive AC power and convert it to an adjustable frequency, adjustable voltage output for controlling motor operation. A typical inverter receives 480 VAC, three-phase, 50 Hz input power and in turn provides the proper voltage and frequency for a given speed to the motor. The three common inverter types are the variable voltage inverter (VVI), current source inverter (CSI), and pulse width modulation (PWM).Another type of AC drive is a cycloconverter. These are commonly used for very large motors and will not be described in this course. All AC drives convert AC to DC, and then through various switching techniques invert the DC into a variable voltage, variable frequency output.

Variable Voltage Inverter (VVI):The variable voltage inverter (VVI) uses an SCR converter bridge to convert the incoming AC voltage into DC. The SCRs provide a means of controlling the value of the rectified DC voltage from 0 to approximately 600 VDC. The L1 choke and C1 capacitor(s) make up the DC link section and smooth the converted DC voltage. The inverter section consists of six switching devices. Various devices can be used such as thyristors, bipolar transistors, MOSFETS, and IGBTs. The following schematic shows an inverter that utilizes bipolar transistors. Control logic (not shown) uses a microprocessor to switch the transistors on and off providing a variable voltage and frequency to the motor.This type of switching is often referred to as six-step because it takes six 60 steps to complete one 360 cycle. Although the motor prefers a smooth sine wave, a six-step output can be satisfactorily used. The main disadvantage is torque pulsation which occurs each time a switching device, such as a bipolar transistor, is switched. The pulsations can be noticeable at low speeds as speed variations in the motor. These speed variations are sometimes referred to as cogging. The non-sinusoidal current waveform causes extra heating in the motor requiring a motor derating.

Current Source Inverter:The current source inverter (CSI) uses an SCR input to produce a variable voltage DC link. The inverter section also uses SCRs for switching the output to the motor. The current source inverter controls the current in the motor. The motor must be carefully matched to the drive.Current spikes, caused by switching, can be seen in the output. At low speeds current pulses can causes the motor to cog.

Pulse Width Modulation:Pulse width modulation (PWM) drives, like the Siemens MICROMASTER and MASTERDRIVE VC, provide a more sinusoidal current output to control frequency and voltage supplied to an AC motor. PWM drives are more efficient and typically provide higher levels of performance. A basic PWM drive consists of a converter, DC link, control logic, and an inverter.

Converter and DC Link:The converter section consists of a fixed diode bridge rectifier which converts the three-phase power supply to a DC voltage. The L1 choke and C1 capacitor(s) smooth the converted DC voltage. The rectified DC value is approximately 1.35 times the line-to-line value of the supply voltage. The rectified DC value is approximately 650 VDC for a 480 VAC supply.

Control Logic and Inverter:Output voltage and frequency to the motor are controlled by the control logic and inverter section. The inverter section consists of six switching devices. Various devices can be used such as thyristors, bipolar transistors, MOSFETS and IGBTs. The following schematic shows an inverter that utilizes IGBTs. The control logic uses a microprocessor to switch the IGBTs on and off providing a variable voltage and frequency to the motor.

IGBTs(Insulated Gate Bipolar Transistor):IGBTs provide a high switching speed necessary for PWM inverter operation. IGBTs are capable of switching on and off several thousand times a second. An IGBT can turn on in less than 400 nanoseconds and off in approximately 500 nanoseconds. An IGBT consists of a gate, collector and an emitter. When a positive voltage (typically +15 VDC) is applied to the gate the IGBT will turn on. This is similar to closing a switch. Current will flow between the collector and emitter. An IGBT is turned off by removing the positive voltage from the gate. During the off state the IGBT gate voltage is normally held at a small negative voltage (-15 VDC) to prevent the device from turning on.

Using Switching Devices to Develop AC Output:In the following example, one phase of a three-phase output is used to show how an AC voltage can be developed. Switches replace the IGBTs. A voltage that alternates between positive and negative is developed by opening and closing switches in a specific sequence. For example, during steps one and two A+ and B- are closed. The output voltage between A and B is positive. During step three A+ and B+ are closed. The difference of potential from A to B is zero. The output voltage is zero. During step four A- and B+ are closed. The output voltage from A to B is negative. The voltage is dependent on the value of the DC voltage and the frequency is dependent on the speed of the switching. An AC sine wave has been added to the output (A-B) to show how AC is simulated.

PWM (Pulse Width Modulation) Output:There are several PWM modulation techniques. It is beyond the scope of this book to describe them all in detail. The following text and illustrations describe a typical pulse width modulation method. An IGBT (or other type switching device) can be switched on connecting the motor to the positive value of DC voltage (650 VDC from the converter). Current flows in the motor. The IGBT is switched on for a short period of time, allowing only a small amount of current to build up in the motor and then switched off. The IGBT is switched on and left on for progressively longer periods of time, allowing current to build up to higher levels until current in the motor reaches a peak. The IGBT is then switched on for progressively shorter periods of time, decreasing current build up in the motor. The negative half of the sine wave is generated by switching an IGBT connected to the negative value of the converted DC voltage.

PWM Voltage and Current:The voltage and frequency is controlled electronically by circuitry within the AC drive. The fixed DC voltage (650 VDC) is modulated or clipped with this method to provide a variable voltage and frequency. At low output frequencies a low output voltage is required. The switching devices are turned on for shorter periods of time. Voltage and current build up in the motor is low. At high output frequencies a high voltage is required. The switching devices are turned on for longer periods of time, allowing voltage and current to build up to higher levels in the motor.

COMPONENT OF DRIVEThe main components of a modern electrical drive are the motors, power processor, control unitand electrical source. These are briefly discussed below.

a) Motors:

Motors obtain power from electrical sources. They convert energy from electrical tomechanical - therefore can be regarded as energy converters. In braking mode, the flow of power is reversed. Depending upon the type of power converters used, it is also possible for the power to be fed back to the sources rather than dissipated as heat. There are several types of motors used in electric drives choice of type used depends onapplications, cost, environmental factors and also the type of sources available.. Broadly, they can be classified as either DC or AC motors:

DC motors (wound or permanent magnet). AC motors: Induction motors squirrel cage, wound rotor. Synchronous motors wound field, permanent magnet. Brushless DC motor require power electronic converters. Stepper motors require power electronic converters. Synchronous reluctance motors or switched reluctance motor.

b) Power Processor or Power Modulator:

Since the electrical sources are normally uncontrollable, it is therefore necessary to be able to control the flow of power to the motor this is achieved using power processor or power modulator. With controllable sources, the motor can be reversed, brake or can be operated with variable speed. Conventional methods used, for example, variable impedance or relays, to shape the voltage or current that is supplied to the motor these methods however are inflexible and inefficient.

Modern electric drives normally used power electronic converters to shape the desired voltage or current suppof the motors can be changed at will. Power electronic converters have several advantages over classical methods of power conversion, such as: More efficient since ideally no losses occur in power electronic converters. Flexible voltage and current can be shaped by simply controlling switching functions of the power converter. Compact smaller, compact and higher ratings solidstate power electronic devices are continuously being developed the prices are getting cheaper.

Converters are used to convert and possibly regulate (i.e. using closed-loop control) the available sources to suit the load i.e. motors. These converters are efficient because the switches operate in either cut-off or saturation modes.Several conversion are possible: AC to DCDC to ACDC to DCAC to AC

c) Control Unit

The complexity of the control unit depends on the desired drive performance and the type of motors used. A controller can be as simple as few op-amps and/or a few digital ICs, or it can be as complex as the combinations of several ASICs and digital signal processors (DSPs).The types of the main controllers can be: Analog - which is noisy, inflexible. However analog circuit ideally has infinite bandwidth. Digital immune to noise, configurable. The bandwidth is obviously smaller than the analog controllers depends on sampling frequency. DSP/microprocessor flexible, lower bandwidth compared to above. DSPs perform faster operation than microprocessors (multiplication in single cycle). With DSP/microp. complex estimations and observers can be easily implemented.

d) Source

Electrical sources or power supplies provide the energy to the electrical motors. For high efficiency operation, the power obtained from the electrical sources need to be regulated using power electronic converters. Power sources can be of AC or DC in nature and normally are uncontrollable, i.e. their magnitudes or frequencies are fixed or depend on the sources of energy such as solar or wind. AC source can be either three-phase or single-phase; 3-phase sources are normally for high power applications.There can be several factors that affect the selection of different configuration of electrical drive system such as:a) Torque and speed profile - determine the ratings of converters and the quadrant of operation required.b) Capital and running cost Drive systems will vary in terms of start-up cost and running cost, e.g. maintenance.c) Space and weight restrictions.d) Environment and location.

Comparison Between DC and AC Drives

Motors :

DC require maintenance, heavy, expensive, speed limited by mechanical construction. AC less maintenance, light, cheaper, robust, high speed (esp. squirrelcage type).

Control unit:

DC drives: Simple control decoupling torque and flux by mechanical commutator the controller can be implemented using simple analog circuit even for high performance torque control cheaper. AC drives, the types of controllers to be used depend on the required drive performance obviously, cost increases with performance. Scalar control drives technique does not require fast processor/DSP whereas in FOC or DTC drives, DSPs or fast processors are normally employed.

Siemens MASTERDRIVES

The Siemens MASTERDRIVES can be used for variable-speed control on motors rated from 1 to 5000 HP. MASTERDRIVES are available for all major worldwide 3-phase supply voltages: 208-230, 380-460, 500-575, 660-690 volts. The Siemens MASTERDRIVES can also be referred to by a model series number, 6SE70.

AC - AC (AC - to - AC):A single inverter can be used with single motor, single motor with a tach, and multimotor applications. This is referred to as the AC-AC version. Various options allow for analog and encoder tachometer types.

DC - AC (DC - to - AC):The Siemens MASTERDRIVES can also be configured so that acommon DC bus supplies power to several AC inverters. Common DC bus systems also allow single and multimotor combinations. This is referred to as the DC-AC version.

Braking unit:In the speed-torque chart there are four quadrants accordingto direction of rotation and direction of torque. Quadrant I is forward motoring or driving (CW). Quadrant III is reverse motoring or driving (CCW). Reverse motoring is achieved by reversing the direction of the rotating magnetic field. The dynamics of certain loads may require four-quadrant operation. When equipped with an optional braking unit Siemens MASTERDRIVES are capable of four-quadrant operation. Braking occurs in quadrants II and IV. Several regenerative rectifier products are also available which return braking energy to the power source instead of dissipating (wasting) it in resistors.

Compact units:Compact units require the smallest mounting space. Units canbe DIN-G rail mounted side-by-side without spacing. There are four sizes: A, B, C, and D. Compact units are available with ratings from 3 to 50 HP (5.6 to 72 Amps) at 460 VAC.

Chassis Units:Chassis units can also be mounted side-by-side without spacing. They are easily mounted on the wall when supplied in an IP20 enclosure. There are four sizes: E, F, G, and K. Chassis units are available with ratings from 60 to 500 HP (83.7 to 590 Amps) at 460 VAC.

Cabinet Units:Cabinet units are ready-wired complete units for single and multimotor applications. All components are accessible from the front of the cabinet. Cabinet units are available with ratings from 50 to 5000 HP (45 to 4500 KW).

Programming and operating sources:The MASTERDRIVES can be programmed and operated from the following sources:Operator Control Panel (OP1S)Parameterization Unit (PMU)Terminal strips on the CU boardSerial interface (various)

Digital tachometers:Digital tachometers (encoders) can be used to measure the actual speed of the motor. The Digital Tachometer Interface (DTI) is designed to be used with digital tachometers (encoders) that operate at a voltage other than 11-30 VDC. The DTI is also required if the following encoders are used:HTL encoder with inverted channel.Floating HTL encoder.TTL encoder.Encoder with cables greater than 495 feet.

Analog tachometers:Analog tachometers can also be used to measure the actual motor speed. Analog tachometers generate a DC voltage which is proportional to the speed. The voltage at maximum speed is a function of the actual tachometer, and generally lies between 10 V and 300 V. Closed loop speed control with an analog tach can be applied to a speed range from 1 RPM to 6000 RPM. An analog tach interface (ATI) board is used to connect an analog tach to the CUVC board.

Applications

When applying an AC drive and motor to an application it is necessary to know the horsepower, torque, and speed characteristics of the load. The following chart shows characteristics of various loads.

Loads generally fall into one of three categories:

Constant torque - The load is essentially the same throughout the speed range. Hoisting gear and belt conveyors are examples.Variable torque - The load increases as speed increases. Pumps and fans are examples.Constant horsepower - The load decreases as speed increases. Winders and rotary cutting machines are examples.

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