straight twist joint1
TRANSCRIPT
WINTER TRAINING
REPORT
SUBMITTED BY
ALISHA AGRAWAL
2K7/EE/808
DELHI TECHNOLOGICAL UNIVERSITY
ACKNOWLEDGEMENTS
I SINCERELY WISH TO PLACE ON RECORD THE CONTINUOUS GUIDANCE, SUPPORT AND ENCOURAGEMENT OF MY GUIDE, ______________________________________________________________,
WITHOUT WHOM MY TRAINING REPORT COULD NOT HAVE SEEN THE LIGHT OF THE DAY. THE TRAINING OWES ITS TIMELY AND SUCCESSFUL COMPLETION TO THE PINPOINT GUIDANCE RENDERED BY HIM.
ALISHA AGRAWAL
2K7/EE/808
DELHI TECHNOLOGICAL UNIVERSITY
STRAIGHT TWIST JOINT
REQUIREMENTS:
TOOLS
Electrician’s knife Steel rule 300 mm Diagonal cutting pliers 150 mm
MATERIALS
PVC insulated copper cable 1/1.12 -2m Cotton mill cloth 30 cm square Sandpaper
PROCEDURE
1) Collect 2 pieces of 1/1.12 PVC copper cable of 0.5m length.2) Straighten the cables.3) Mark 80 mm length on one end of each piece of cable.
4) Use the knife at an angle 20 degree and remove the insulation from each conductor for a distance of 80 mm.
5) Clean the ends with the help of a cotton cloth.6) Place the conductors together, about 50 mm from the ends.7) Twist them tightly around each other in opposite directions.8) Cut off excess length of the conductor with side cutters.9) Press the sharp end of the conductor and smoothen it.10) Cut off the joint after leaving 30mm cable from the joint.
RAT-TAIL JOINT
PROCEDURE
1) Collect 2 pieces of 1/1.12mm PVC copper cable of 0.5m length.2) Straighten the cables.3) Skin both the ends for 50 mm.4) Clean the conductor ends with the help of cotton cloth.5) Cross the bare wires at an angle of 45 degree and at a distance of 45mm from the cable end.6) Tightly twist the ends.7) Make at least 6 twists.8) Fold the remaining wire back on the twists.
9) Press the ends of the wire with the help of combination pliers to avoid sharp ends and cut off the excess wire.
MARRIED JOINT IN STRANDED CONDUCTORS
REQUIREMENTS:
TOOLS
Electrician’s knife. Steel rule 300mm stainless steel. Diagonal cutting pliers 150mm. Wooden mallet 75 mm dia. Head with handle.
MATERIALS
PVC insulated copper cable 7/0.914 -1m Cotton cloth 30*30cm and sand paper.
PROCEDURE
1) Collect 2 pieces of PVC sheathed copper cable of length 0.5m.2) Mark both cables at 120 mm from the cable ends.3) Remove the insulation for 120 mm on both the cables.4) Open the strands clean the wires and re-twist the strands on original direction upto 50mm
from the cable insulation.5) Cut the centre strand of both the cables close to the twist.6) Make a binding on the twisted part of one cable end.7) Interlace the strands keeping the centres butt.8) Hold the cable end in one hand and twist the strand of the other cable end over it one by one,
closely and tightly.9) Remove the binding made at step 6.10) Repeat the operation as in step 8 on the other side with the second cable end.11) Complete the joint by rounding off the twisted strands with a mallet and cut off the excess
wires.
TEE JOINT IN STRANDED CONDUCTORS
PROCEDURE:
1) Collect two pieces of PVC insulated stranded copper cable. Indicate one piece as ’through cable’.
2) Mark the point of tap in the ‘through cable’ and mark 60mm on either side of the tap point for the insulation to be removed.
3) Remove 60mm insulation on either side of the ‘through cable’ from the point of tap.4) Remove the insulation for 180 mm at the end of the ‘tap cable’.5) Open the strands of the ‘tap cable’ and clean them using sandpaper.6) Re-twist the strands in the original direction upto 50 mm from insulation and make a binding
on the twist part of the ‘tap cable’.7) Untwist the through cable to provide an opening at the point of tap.8) Insert the centre strand of the ’tap cable’ in the opening of the through cable. 9) Wrap three strands of the ‘tap cable’ around the ‘through cable’ on either side of the tap point
to form shoulder on the ‘through cable’.
10) Wrap the strands upto 50 mm to leave a 10 mm gap between the insulation and the shoulders and trim off the excess length of strands.
11) Remove the binding from the ‘tap cable’, wrap the centre strand of the ‘tap cable’ around the through cable and wrap it in the place of binding.
12) Round up the ends with the combination pliers to avoid sharp edges of the strands.
STATOR DESIGN
AIM:
To design a winding for 3-phase, 4-pole, 36 slots distributed and balanced single layer winding
THEORY:
AC WINDINGS
AC Windings are generally of a 3-phase kind because of the inherent advantages of a 3-phase machine. The armature coils must be connected to yield balanced (equal in magnitude and successive phase difference of 2*pi/3 radians) 3-phase emf’s to begin with slots around the armature periphery must be divided into phase bands.
SOME WINDING TERMS
Coil groups = no. of poles x no. of phases
Balanced Winding = number of coils per group are same
Unbalanced Winding = number of coils per group are different
Single Layer= 1 conductor per layer
The winding used in rotating electrical machines can be classified as:
1. Concentrated windings2. Distributed windings
In concentrated windings all the winding turns are wound together in series to form a multi-form coil. In distributed windings, all the winding turns are arranged in several full pitch or fractional pitch coils.
Armature windings are classified into 2 categories:
1. Closed winding2. Open winding
The closed windings are used only for commutator machines, such as d.c. and a.c. commutator machines. Open windings terminate at suitable no. of slip rings or terminals.
One coil with any number of turns has two coil sides and number of conductors in any coil-sides is equal to number of turns in that coil.
POLE PITCH:
A pole pitch is defined as peripheral distance between identical points on adjacent poles. Pole pitch is always equal to 180 electrical degrees.
COIL-SPAN OR COIL-PITCH:
The distance between two coil-sides of a coil is called coil-span or coil-pitch. If the coil-pitch is equal to the pole pitch, then the coil is termed as full pitched coil. In case the coil- pitch is less than pole-pitch, then it is called chorded, short pitch or fractional –pitch coil.
If there are S slots and P poles, then
POLE PITCH = S ∕ P slots per ole
If coil pitch = S ∕ P, it results in full pitch winding .in case coil pitch < S ∕ P, it results in chorded, short pitch or fractional –pitch winding. The coil pitch is rarely greater than pole pitch.
The simple closed windings are of two types, namely
a) Simplex lap windingb) Simplex wave winding
In simplex lap winding, the coils are connected to the adjacent commutator segments.
In simplex wave winding, the coil ends of a coil are bent in opposite directions and connected to commutator segments, which are approximately two pole-pitchers (360 electrical degrees) apart.
WINDING PITCH
The distance between the two consecutive and similar top, coil sides, as the winding progresses, is called the winding pitch.
TYPES OF SLOTS
a) Closed typeb) Semi-closed typec) Open type
PHASE GROUPING
Initially a simple case will be assumed where SPP is an integral number; such winding is referred to as integral slot winding. For illustrative purposes, let m =2 which means 12 slots per pole pair for a 3 phase armature. Slot angle is 360° ∕12 =30°. Further let the coil pitch be full six slots. Six slots are under the influence of one pole with a particular direction of emf s and the remaining 6 slots are under the opposite pole with opposite direction of emf.
DESIGN
36 slots
A B C A B C A B C
1-8 3-10 5-12 7-14 9-16 11-18 13-20 15-22 17-24
A B C A B C A B C
19-26 21-28 23-30 25-32 27-34 29-36 31-2 33-4 35-6
PHASE A = 1-8, 7-14, 13-20, 19-26, 25-32, 31-2
PHASE B = 3-10, 9 -16, 15-22, 21-28, 27-34, 33-4
PHASE C = 5-12, 11-18, 17-24, 23-30, 29-36, 35-6
ESTIMATION OF ELECTRICAL LOAD
Following standards are used:
Fluorescent tube 60 W
Ceiling fan 100 W
Light socket 5A, 100 W
Power socket 15A, 1000W
Diversity factor = 66% for light fan and socket loads
LOAD POWER SYSTEM LAB
No. of tubes =96 load= 96 x 60=6760 W
No. of fans = 24 load =24x 100 =2400 W
No. of light socket = 0 load = 0 x 100 = 0W
No. of power socket =16 load=16 x 1000 = 16000W
TOTAL LOAD=24160 W
Actual load = LOAD with diversity factor
= 24160 x 0.66
= 15.95 KW
ESTIMATION OF ELECTRICAL LOAD
Following standards are used:
Fluorescent tube 60W
Ceiling Fan 100W
Light Socket 5A, 100W
Power Socket 15A, 1000W
Diversity Factor = 66% for light, fan and socket loads
LOAD- JUNIOR MACHINE LAB
No. of tubes = 96 load=96X60=6760 W
No. of fans = 24 load=24X100=2400 W
No. of light socket = 6 load=6X100=600 W
No. of power socket = 16 load=16X1000=16000 W
TOTAL LOAD = 24760 W
Actual Load = Load with Diversity factor
= 66% of 24760
= 16.34 KW
Motor Load = 34 hp
= 25.364 KW
DC Load
Rectifier = 200V, 70 A
Motor Load = 17 KW
Total Load = 58.756 KW
SPECIFICATIONS OF ELECTRICAL EQUIPMENTS IN SENIOR MACHINE LABAROTARY
SYCHROSCOPE : 400 V, 50 Hz, AC with external resistance
By Ferranti
SWITCH FUSE TYPE LP32 : Ue: 415 V~ 50 Hz, Ie: 32A AC22
Gec Alstom India Limited
MCB DISTRIBUTION BOARD : Rated current: 200 A, AC ~ 240/415, 50 Hz
Capacity: ~ 15 KA
Type: TPN
Montel (Delhi control devices Pvt. Limited)
EARTH LEAKAGE CIRCUIT BREAKER : 63 A/4 (240/415 V)
IDN = 300mA
Neptune 2000
3 PHASE 4 WIRE CONTROLLED SWITCH : 63A, 240-415 A
LOADING RHEOSTAT : 3KW, 1 phase
230 V, 13 Amps
Premier Trading Corp, Meerut
INDUCTION MOTOR : 7.5 HP, delta 3 phase, 50 cycles
400/440 V, 995 rpm, 11.3 A
Bradford near England
DIRECT CURRENT MOTOR : 4HP, 220 V, 16.7 A, 1500 rpm
The general electric comp, hd.
DIRECT CURRENT GENERATOR : 3 KW, 13.7 A, 1600 rpm, 220 V
Insul-class-E, winding-compound
Kirloskar Electric company, Ltd. Bangalore
EDDY CURRENT DYNAMOMETER : Br.Torque- 0.7 Kgm, 3 HP, at 3000 rpm
Tachogenerator AC 1000 rpm, 10V rms, poles 48
Dynaspede
CONT. VARIABLE AUTO TRANSFORMER : Max Load- 16 Amp
Input 240 V, 50-60 Hz,
Output 0-240 Hz and 0-270 Hz
Servkon System Pvt. Limited
SINGLE CORE RHEOSTAT : 45 ohm,5 A or 1000 ohm, 2.2 A
MCCB : Max 600 V AC 50 Hz
Interrupting capacity 10 KA at 415 KV
Crompton Greaves
3 PHASE ALTERNATOR : 3 KVA, 0.8 pf, 49 Hz, 230 V, 7.5A, 1470 rpm
GEC( general electric co. ltd.)
AIR BREAK STARTER : 230 V, 50 Hz
Full load current range – 30A
Associated Electric Industries Ltd.
3 PHASE VARIAC : Input 415 V, 3 phase, 50/60 Hz
Output 0-415 V, Output current 15 A per line
Paradise Industries
HI-TECH AUTO TRANSFORMER : Input Voltage, 3 phase 50/60 Hz
Output Voltage 0-470 V, 3 phase
Current rating- 15 A
Seven star, Jawahar Nagar, Delhi
SENSIBLE RHEOSTAT : Ohms- 1000
Amp- 1.4
Stead electronic industries
DC BRUSH CARRIAGE MOTOR : Max rpm–4000, Volts–220(field), Volt 20/250(armature)
Amp- 0.5(armature)
Mawdsley’s lid
3 PHASE WATTMETER FOR 3 : Voltage -300/600 V, Current- 5-10A
PHASE BALANCED/ UNBALANCED 2 element electrodynamometer type
LOAD Insulation resistance above 20 MΩ
POWER CAPACITOR : 10 KVA, 440/415 V, 50 Hz, 3 Phase 3 wire, delta connection
12.10A, Ambient-50 C max, wt.-4 Kg
Priya Power Capacitor
INDUCTIVE LOADING BANK : 230 V. 50 Hz, 0-230 A , 0.04 pf ,5 KVA
Made in England
1PHASE INDUCTIVE LOAD : 0.8 pf; lagging, 230 V, 50 Hz , 0-230 A, 5 KVA
INDUCTION MOTOR : 1 HP, 220/230 V, 1 phase, 50 Hz, 7.6 A
Class 1: Amb. 40 C
Start Capacitor 120μF, 275 V
Crompton Greaves
3 PHASE I.M : 0.55KW, 0.75 HP
1405 rpm, 0.78 pf , 50Hz
Insul-class-F
Bharat Bizlee Ltd.
DC GENERATOR COUPLED WITH DC MOTOR
DC generator DC motor
1.7KW 3.7KW
1500rpm 1500rpm
220V 220V
16.82A 16.82 A
Wdg. Shunt wdg. Compound
Duty S1 duty S1
Exc. 220V/0.84 A Exc. 220 V, 0.36 A
Insulation F Insulation F
Kirloskar electric co. ltd Banglore
CHOKE COIL DESIGN
In arc discharge lamps, the effective resistance of the lamp decrease as the arc current increases and external impedance is required to limit this current. The requirements of such impedance are as follows:
It should provide favorable starting condition for lamp. It should provide sufficient drop so that the voltage across the lamp does not exceed a pre
determined value. The current waveform should not be distorted otherwise it results in radio interference. The power consumption is minimum. It should be noise free.
A choke satisfies almost all the requirements of good ballast , which consist of a coil of insulated wire wound on a laminated iron core containing an air gap.
For maximum efficiency, the design of the core and the winding should be such that the core loss equals the copper loss whereas for minimum cost, the cost of the core should be equal to the cost of the winding.
The choice design should be such that it should never operate in the saturation region as this would result in reduction in inductance, which is not desirable. This necessitates a suitable air gap to be provided in the choke. in practice it is difficult to calculate the size of the air gap accurately due to the effects of magnetic fringing . So, the air gap is finally set on a test bench during manufacture.
The shape of a choke is determined by the necessity to house the choke in a particular fitting. The spine is made as slim as possible for reasons of appearance and cost, even though it is known, that cubic chokes are more efficient.
Let V be the supply voltage, the resistive voltage drop in the choice coil. ,the drop across
the lamp. the reactive drop in the choke coil and the drop across the choke.
Since is resistive.
And
Normally, =10 to 15 percent of . Also depends upon the tube length and is known .V is
known in any case, therefore Can be obtained. The next step is to calculate the number of turns in the choke.
Number of turns =
For silicon iron, the flux density ( ) can be taken to be 1.2 to 1.3 Wb / and the area of the
core ( ) is obtained using the empirical relation
Area in c , =
The value of area may be modified slightly depending upon the availability of size of stampings.
In our case, Power =40 watts
Therefore = =1.133c
Substituting the value of area and flux density in the above expression we get
No. of turns= 750(approx)
The size of the wire is selected which governs the copper loss in the windings and hence the
temperature rise of the coil .A current density of 300 to 400 A/ is usually found satisfactory. A suitable value of air gap to give the desired flux density is obtained
Length of air gap =
Where
=amp turns of air gap=total amp turns – iron amp turns
= amp turns of air
The core material used is silicon steel with 1 to 2 % silicon. The thickness of the laminations is 0.5 mm. the wire used winding super-enameled copper wire and each layer of the winding is separated from next layer by a strip of paper. The resistance of wire for an 80 watts tube is approximately 10Ω, and the ohmic loss of the choke is about 10 to 15 watts. the use of a choke along with an electric discharge lamp lowers the p.f. to as low as 0.5. To achieve a p.f. of 0.8 a capacitor of suitable value is connected across the supply.
WHAT IS ‘EARTHING’?
Earthing may be defined as a system of electrical connections to the general mass of earth. The characteristics primarily determining the effectiveness of an earth electrode is the resistance which it provides between the earthing system and the general mass of the earth.
PURPOSE OF EARTHING:
The objectives of earthing installations are:
To provide protection to animals and humans against the danger of electric shock. To maintain the proper function of electrical system.
CHIEF REQUIREMENT OF GOOD EARTHING – LOW SOIL RESISTIVITY
Soil Resistivity (the specific resistance of soil) is usually measured in Ohm metres. One ohm metre being the resistivity the soil has when it has a resistance of one ohm between the opposite faces of a cube of soil having one metre sides.
The unit commonly used is Ohm centimetre; to convert Ohm metre to Ohm centimetre, miultiply by 100.
Soil resistivity varies greatly from one location to another. For example, soil around the banks of the river has a resistivity in order of 1.5 Ohm metres. In the other extreme, dry sand in elevated areas can have values as high as 10, 000 Ohm metres.
TYPES OF EARTHING
Earthing a tower/ equipment means connecting a tower/ equipment to general mass of earth by means of an electrical conductor. Connection to earth is achieved by embedding a metal plate/ pipe / rod or any other conductor with large surface for quick dissipation. This metal plate/ rod/ conductor is called an “Earth Electrode”. Earth electrodes can be of different shapes and size and can be and can be put in ground in different configurations. Choice for type of earthing and earth electrodes depends upon the type of soil and the required quality of earth pit resistance.
Different types of electrodes conventionally used are:
1. Metal Plates (Copper or Galvanized iron) rectangular/ square/ circular placed vertically and at times horizontally in the ground. Plates of 600mm X 600mm with a thickness of 2 to 6 mm are mostly used. Plates of 200mm X 300 mm added to pipes are also used.
2. Metal pipes / rods of Galvanized Iron, Copper, stainless steel and copper coated MS rods are driven deep into ground and connected to the down con ductor.
3. In rocks, the GI tapes / Copper tapes of 25 mm or 50 mm width and 2, 3 or 5 mm thickness are laid horizontally in the ground upper crest.
4. Graphite Rods and Dynamic electrodes are also in use with advance technology.
Common types of Earthing Systems in use can be classified as below:
a. Deep Driven Earthing: Metal rods, pipes, plates or dynamic electrodes are driven into the ground, atleast 10 feet and more for good dissipation. They are linked to the inspection joint.
b. Trench Electrodes: In rocky areas or sea beds, the metal tapes are laid in ½ metre deep trenches of length as per the required resistance (minimum of 30 feet length is required). Shorter lengths in parallel, duly interconnected or single length depending on the space available are used.
c. Ground Grid Mesh Electrodes: Combination of plates and rods of identical metals are put deep in ground for grid mesh earthing. Normally used for big electrical installations.
d. Equipotential Bonding: In order to achieve a common earth base at any installation, this bonding is done in which all earth pits are connected with a ring earth through the 35 mm squared copper cable. The communication earth should be connected with the ring earth through Isolation Spark Gap. It creates the redundancy and at no stage the system is exposed to any kind of surge. The ring earth is normally of copper tape 25mm X 3 mm put ½ metre deep in ground or around the wall depending on the prevailing situation.
SELECTED FEATURES OF ELECTRICITY REGULATIONS IN INDIA
Regulation Salient FeaturesCentral Acts and Rules Relating to Electricity
The Indian Electricity Act, 1910 Issue of Licenses Regulatory and safety aspects Rules for non licenses Guidelines for electrical work Guidelines for determination of purchase prices and
chargesThe Electricity Supply Act, 1948 Formal establishment of SEB and generating
companies Power and duties of the above entities with guidelines
for work and trading procedure Approval process for generating stations Guidelines for licensee staff Procedures for finance, accounts & audit
The Indian Electricity Rules, 1956 Mainly technical guidelines and rules for worksThe Central Electricity Authority Rules, 1977 Defining the functions and duties of CEAThe Central Electricity Authority Regulations, 1979
Lays down desired operational details for smooth functioning of CEA
The Electricity Wires, Cables, Appliances & Accessories (Quality control) order, 1993
Quality control, Certification of manufacturers Guidelines for storage, sale & distribution
Policy On Private Participation in Private Sector, 1991
The main objective is to attract private investment Upto 100% foreign equity participation permissible
The Electricity Laws(Amendment) Act, 1991 Increased authority of regional load dispatch centres(RLDC), Grid integration
The Electricity Laws(Amendment) Act, 1998 Formal establishment of central and state transmission utilities as public companies
Independent standing for transmissionThe Electricity Regulatory Commissions Act, 1998
Establishment of CERC with provisions for SERCs Guidelines for tariffs, supply & service.
Fee for Testing & Inspection, GOI Order, 1998 Standardizing fees for testing and inspection by electrical inspectors
Other Acts and Rules Affecting the Electricity SectorThe Atomic Energy Act, 1962 Fix rates and regulate supply of electricity from atomic
stationsThe Consumer Protection Act, 1986 Protection of consumer interests by establishing
consumer councils & other authorities for settlement of disputes
The Electricity (Supply) Annual Accounts Rules, 1985
Provision for establishment of Bureau of Energy Efficiency – implementation guidelines
The Energy Conservation Act, 2001Indian Standards(IS), laid down by BIS
Technical standards for equipments and works