December 24, 2012

DEFINITIONS :


                                                                                                                                                                                         
Auto-transformer :     
A transformer used to step voltage up or down. The primary and secondary wingdings share common turns,  and it provides no isolation.

ARMATURE       :    The part of an electric generator in which the voltage is induced.

Armature              :    A winding that develops current output from a generator when it turns cut a magnetic                                                   
                                   flux.

Arc                        :    Sparking that results when undesirable current flows between two points of differing  
                                   potential. This may be due to leakage through the intermediate insulation or a leakage 
                                   path due to contamination.
      
Amplitude            :    The maximum value of a wave.

Alternating Current : (AC) A current which periodically changes its direction .

Alternating Voltage   :  A voltage which periodically changes its polarity.

1.   What is electric network?
A. The interconnection of two (or) more circuit elements called as electric network.

2.  What is ohm's law ?
A. Temperature remaining constant.The potential difference across the ends of the conductor is directly proportional to the current flowing through it
        
                                    V  ∝ I or V = IR 

3. What is power?   
A. The power absorbed by the resistor is given by P = IR 
                                                                               =  I²R Watts 

4. What is conductance ?
A. The reciprocal of resistance is called as conductance units are mho .


December 20, 2012


                                         TRANSFORMERS


HISTORY OF TRANSFORMER :

**********************

FOUNDERS OF TRANSFORMER :

                                              Founders of the transformer Otto Bláthy, Miksa Deri, Károly Zipernowsky of the Austro-Hungarian Empire First designed and used the transformer in both experimental, and commercian systems. Later on Lucien Gaulard,Sebstian Ferranti, and William Stanley perfected the design. But The property of induction was discovered in the 1830's but it wasn't until 1886 that William Stanley, working for Westinghouse built the first refined, commercially used transformer. His work was built upon some rudimentary designs by the Ganz Company in Hungary (ZBD Transformer 1878), and Lucien Gaulard and John Dixon Gibbs in England. Nikola Tesla did not invent the transformer as some dubious sources have claimed. The Europeans mentioned above did the first work in the field, George Westinghouse and Stanley made the transformer cheap to produce, and easy to adjust for final use.
               Ottó BláthyMiksa Déri, Károly Zipernowsky created the "Z.B.D Transformer" 


The first transformer




William Stanley's First Transformer built in 1885
Stanley's first transformer which was used in the electrification of Great Barrington, Massachusetts in 1886
                  "The first  AC power system that used the modern transformer was in the great barring-ton,Massachusetts in 1886 Earlier forms of the transformer were used in Austro-Hungary 1878-1880s and 1882 onward in England.Lucien Gualard (French Man) used his AC system for the revolutionary Lanzo to Turin electrical exposition in 1884(i.e, northern Italy) In 1891 Mastermind Mikhail Dobrovsky designed and demonstrated his 3 phase transformer in the Electro-Technical exposition Frankfurt,Germany.


TRANSFORMER DEVELOPMENT TIME LINES:

1830s - Joseph Henry and Michael Faraday work with electromagnets and discover the property of induction independently on separate continents.

1836 - Rev. Nicholas Callan of Maynooth College, Ireland invents the induction coil

1876 - Pavel Yablochkov uses induction coils in his lighting system

1878 -1883 - The Ganz Company (Budapest, Hungary) uses induction coils in their lighting systems with AC incandescent systems. This is the first appearance and use of the toroidal shaped transformer.

1881 - Charles F. Brush of the Brush Electric Company in Cleveland, Ohio develops his own design of transformer (source: Brush Transformers Inc.)  



Definition of Transformer : 

                                                    A transformer  converts an alternating (A/C)currentof a certain voltage to an alternating current of different voltage, without change offrequency by electromagnetic induction A 'step up' transformer receives a low voltage and converts into a higher voltage, and a 'step down' transformer does just the reverse.

                        A transformer is an electrical device that transfers energy from one circuit to another purely by magnetic coupling. Relative motion of the parts of the transformer is not required for transfer of energy. Transformers are often used to convert between high and low voltages, to change impedance, and to provide electrical isolation between circuits.

Introduction : 

                         The transformer is one of the simplest of electrical devices. Its basic design, materials, and principles have changed little over the last one hundred years, yet transformer designs and materials continue to be improved. Transformers are essential in high voltage power transmission providing an economical means of transmitting power over large distances. The simplicity, reliability, and economy of conversion of voltages by transformers was the principal factor in the selection of alternating current power transmission in the "War of Currents" in the late 1880's. In electronic circuitry, new methods of circuit design have replaced some of the applications of transformers, but electronic technology has also developed new transformer designs and applications.
                         Transformers come in a range of sizes from a thumbnail-sized coupling transformer hidden inside a stage microphone to gigawatt units used to interconnect large portions of national power grids, all operating with the same basic principles and with many similarities in their parts.                      

                         A transformer has no internal moving parts, and it transfers energy from one circuit to another by electromagnetic induction. External cooling may include heat ex changers, radiators, fans, and oil pumps. Radiators and fans are evident The large horizontal tank at the top is a conservator. Transformers are typically used because a change in voltage is needed. 

                 The following figure shows the basic diagram of a transformer



A simple transformer consists of two electrical conductors called the primary winding and the secondary winding. If a time-varying voltage {v_P}\, is applied to the primary winding of N_P\, turns, a current will flow in it producing a magneto-motive force(MMF). Just as an electromotive force (EMF)  drives current around an electric circuit, so MMF drives magnetic flux through a magnetic circuit. The primary MMF produces a varying magnetic flux  \Phi_P\, in the core (shaded grey), and induces a back  electromotive force (EMF) in opposition to {v_P}\,
                               According to the Faraday's law,The voltage induced across the primary winding is proportional to the rate of change of flux  :
         {v_P} = {N_P} \frac {d \Phi_P}{dt}

Similarly, the voltage induced across the secondary winding is:
{v_S} = {N_S} \frac {d \Phi_S}{dt}
With perfect flux coupling, the flux in the secondary winding will be equal to that in the primary winding, and so we can equate \Phi_P\, and\Phi_S\,. It thus follows that:
\frac{v_P}{v_S}=\frac{N_P}{N_S}.

                   Hence,In an ideal transformer the ratio of primary and secondary voltages is equal to the ratio of number of turns in their winding's.The voltage per turn is same in the both winding's.The most common use of the transformer: to convert electrical energy at one voltage to energy at a different voltage by means of winding's with different numbers of turns.
   

EMF equation

If the flux in the core is sinusoidal, the relationship for either winding between its number of turns, voltage, magnetic flux density and core cross-sectional area is given by the universal emf equation:
E=4.44 \cdot f \cdot N \cdot a \cdot B
Where E\, is the sinusoidal root mean square voltage of the winding, f\, is the frequency in hertz, N\, is the number of turns of wire, a\, is the cross-sectional area of the core and B\, is the peak magnetic flux density in Tesla The value 4.44 collects a number of constants required by the system of units.

Types of transformers : 
                         
         1 . Step-up
The secondary has more turns than the primary

2 . Step-down
The secondary has fewer turns than the primary



3 . Isolating
Intended to transform from one voltage to the same voltage. The two coils have approximately equal numbers of turns, although often there is a slight difference in the number of turns, in order to compensate for losses (otherwise the output voltage would be a little less than, rather than the same as, the input voltage)



4 . Variable
The primary and secondary have an adjustable number of turns which can be selected without reconnecting the transformer.





















DC CIRCUIT\

CAPACITORS
FUSE




RESISTOR 

OMCAP

OM CAP


Overseas Manpower Company Andhra Pradesh Limited (OMCAP) is a recruiting Agency launched by Government of Andhra Pradesh and operates under the approval issued by Protector General of Emigrants, Ministry of Labour Government of India. The Board of Directors of the company are senior officials of Government of Andhra Pradesh. The main objective of the company is to help the overseas job aspirants from the exploitation of unauthorized and unscrupulous Placement agencies.

The demand for skilled labor is increasing in Global market (Middle East, North America, Europe, Australia & Africa). Workers with advanced technical skills, multiple skills are sought by foreign employers. Unskilled / Semi Skilled workers are subjected to exploitation, low wages and ill treatment.

Objectives:

  • To train workers to the overseas standards
  • To familiarize workers with overseas work conditions, work environment
  • To test the skills and provide skill certification
  • To facilitate placement of the trained in overseas jobs
TargetTraining Candidates in the following Identified demand trades:

Masons, Scoff Holders, Erectors, Welders (3G, 6G, 10G, Mig, Tig, Saw) Fabricators, A/C Technicians, cable Technicians, Electricians, Pipe Fitters, Shuttering Carpenters, Dozer Operators, Dumper drivers, Crane Operators, Riggers, Surveyors, Security Guards, Supervisors, Office Attendents, Accountants, Ayah/House Maid, Nurses, Caretakers etc.,

Training CentersNational Academy of Construction (NAC), ITI's at old and new Vizag, Vizainagaram, Vijayawada, Ananthapur, Kadapa, Warangal, Mallepally, Hyderabad, Bhongir, Westin Hotel Management Institute Vijayawada, Star HR Academy, Hyd, KDLOA Model Driving School, Vijayawada, Excel Securities Academy Hyd etc.,

TrainersTraining Officers from NAC, ITI's and Trainers deputed by Overseas Employers

TraineesCandidates registered with OMCAP and Employment Exchanges in AP state, numbering about 22 lakhs. The candidates will be screened and selected by OMCAP in the presence of representatives of overseas employers.

Training Modules
  • Formulated in association with Overseas Clients.
  • Evaluation Testing and Certification
  • By Training Provider (NCVT, MES) OMCAP & Overseas Clients. (OC's)
Time15 days to 3 months with Placement Assistance

FundingThe project is funded by Rajiv Udyogasri (RUS), Government of Andhra Pradesh & Ministry of Overseas Indian Affairs (MOIA) and Government of India

PlacementsData bank of job seekers & Overseas Employers identification of vacancies abroad foreign visits, Field trips, Correspondence by post, E-Mail.

Identification of informers in foreign countries Opening of branch offices in gulf, Malaysia, U.S. Signing MOUs with agents, consultants, Training Providers and Employers in foreign countries. Studying the Labor markets for assessment of requirements of manpower country – wise. Awareness programs, Campaigns.

Passport and Visa AssistanceOverseas Manpower Company Andhra Pradesh Limited (OMCAP) is having liaison with Embassies, Travel Operators and Passport Authorities Passport, Visa, Air Ticketing assistance will be provided.

Registration Process:Candidates who seek registration with OMCAP should possess at least 2 years experience in the relevant post for which he desires to be considered and should hold a valid passport. The candidates without experience also will be registered. 

Data Bank: The Company will maintain a computerized Data Bank of registrants. Details of data stored can even be analyzed with reference to certain parameters and provided to marketing agencies on a cost basis for promoting their products to the registrants.

Enroll as Trainee:To Register at OMCAP choose your login and password and fill in the details in the registration page and click submit. Use your login and password details given while registering to login into your account.

For more details on 
http://omc.ap.gov.in/