Electrical Engineering Hand written notes-old

Dear All ,

Here iam uploading some hand written notes.Might be usefull some for  exams.you can download it.
power system
control system
networks
Measurments
digitals

Electrical Engineering Hand written notes-old

Dear All ,

Here iam uploading some hand written notes.Might be usefull some for  exams.you can download it.
power system
control system
networks
Measurments
digitals

Gate-2017 Application form

Dear All,
The Gate-2107 organizing Institute is IIT-Roorkee, is released the application form and important dates.
Please follow the below link to apply.

Gate-2017 Application form-clik here

apgenco,aptransco assistant engineer posts -2016

Dear all,
AP CM ,has given the permission to release the assistant engineer posts in andhra pradesh.
start prpearation.
anytime the notification will b released.
thanku.

ESE 2016 written test results

Hi,

UPSC declares the results of ESE-2016.

clik here to view

how to prepare for Transco ,genco and discoms for Assistant Engineers

Hi ,
for every dream there should be a will ,dedication and passion towards the success.
Same thing will be applicable for getting the asst.engineer job in transco genco and discoms in telangana.
The test will be purely basics only .the standard of the paper is very low at the same time paper is based on basic concepts ,here u should have the strong basics for all the subjects .
In this blog i have mentioned the subjects and authors

what is commutation failure called??

If circuit turn off time is lesser than device turnoff time excess charge carriers are still present in the device .The next operation to turn on the SCR if anode  +ve w.r.t. cathode,SCR will turn on before the gate signal is given.Here the SCR is losing forward blocking capability and behaving as a diode ..is called commutation failure.

significance of gate current for SCR !!!

when the gate current is applied at the gate terminal of SCR ,a significant number of electrons from n2 layer cross the junction J3. It is because N2 layer is heavily doped as compared to p2 layer.after crossing the junction j3 ,these electrons diffuse through p2 layer .the electrons are then swept across junction j2 into the n1 layer .These electrons in n1 layer reduce the positive space charge on the n1 side of depletion layer .
this leads to reduction of the width of depletion layer around the junction j2.
resuslts ..SCR tunrs ON..

GATE -Electrical engineering reference books

GATE -Electrical engineering reference books

Power System -C.L.Wadhava


Electric Machines -P.S.Bimbra

Control System-Ogatta ,kuo

Power Electronics -P.s.Bimbra

Measurments -A.K.Sahwney

Networks -Van valeknburg

Digital Electronics -Morris mano

Analog Electronics -Millman Halkies

EMF -Sadique And william hayt

TSPSC PREVIOUS PAPERS

Dear All ,

Here iam uploading some TSPSC previous papers.Might be usefull some for tspsc exams.

clok here

POWER ELECTRONCIS

Def: power is technology associated with efficient conversion and control of electric power by using power semi conductor devices.

 

Signal level	Power level
Volt: upto 30v	Several volts to KV
I: micro to milli amps	‘A’ to ‘KA’
P:several mW to few Watts	Watts to MW
High level doping is used	Low level doping is used

Applications :there is no boundary for applications of power electronic concepts.

1.Speed control of electric motors.

2.HVDC

3.Wind applications

4.Domestic applications

5.medical Applications

6.satellite applications

Adv:

1.Low losses

2.losses less means heat delivered by the equipment is also.

3.heat lessà size is less

4.reliability  more.

Dis :

1. Harmonics

2. The input power factor of phase controlled rectifier &AC voltage regulator is low when firing angle increases.

Realisation of switch :

Ideal switch :
V_on =  0

I_off =  0

P_on = 0  conduction loss

P_off = 0  Blocking loss

· Ideal switch can change its state instantaneously/ switching time is zero. If switching time is zero means switching frequency is infinite with zero switching loss.

· Ideal switch does not require external energy to change its state from ON to OFF /OFF to ON.

· Thermally stable .

                                                                                                                                                

Real switch:

V_on ≠ 0

I_off   ≠  0

P_on ≠ 0  conduction loss

P_off ≠ 0  Blocking loss

· The real switch will take finite time to change its transition from  ON to OFF /off to ON.

So,switching frequency is limited.

Avg switching power is not zero.

· It requires external energy to change its state .

Types of switches :

1.Uncontrolled switch (passive switch)

Ex:Diode 

2. semi controlled switch  (Active switch)

Ex.SCR

3.Fully controlled switch(active switch)

Ex.BJT,IGBT,MOSFET

power converter

Abstract: Because of grid faults and generator faults disturbance will be created in the supply voltage .In case of unbalanced voltage source, the converters suffer from the problems of power oscillations and over current problems. These problems can be solved by controlling the positive and negative sequence currents. In this paper, a new control strategy is established by utilising the zero sequence components to enhance the power control ability. The paper explains how to use the zero sequence current controls and circuit topologies and concludes with operation with better performance in the delivered power and the load current when the supply voltage unbalanced.

Index: dc-ac converters, zero sequence converter, unbalanced supply voltage

 I.Introduction

Power Electronics plays a vital role in the power control and conditioning. In so many applications of power electronics like solar energy , wind generation, in speed control of dc motor  and renewable energy sources. The power control and conditioning can be acheieved by power electronic components i.e., converters[1], [2].  A conventional dc–ac voltage source converter is shown in fig which is used to convert the dc voltage to three phase AC sources generating units and depending upon the loads and applications[3]–[5].  

Since  the power electronics are very important and essential in the energy conversion technology , the failures and faults may introduce the serious problems in  converters .There is a need to increase the reliability of power electronic converters in many applications to withstand failures and faults [6]–[13]. A good example can be seen in the wind power application, where both the total installed capacity and individual capacity of the power conversion system are relatively

high. The sudden disconnection of the power converter may cause significant impacts on the grid stability and also on the high cost for maintenance/repair [1].

            Because of disturbances and faults the ac source from  the converters  becomes distorted, These unbalanced ac voltage is a big challenge to control the converter operation [2],[14] .Existing control methods  which can regulate both the positive and negative sequence are introduced to  handle these disturbances[2], [16]–[21].The performance by these methods are up to some extent only in distorted power  oscillations and distorted load current oscillations and considering cost of the power converter design. 

This paper presents the improvement in power control limits of a three phase dc-ac converter system for unbalanced ac source. A new approach has been implemented to resolve the issues and enhance the power control capability.

This new approach is utilising the zero sequence components in the converters under other applications like where the unbalanced ac source is to be presented; in that way basic principle and feasibility are mainly focussed.

II. LIMITATIONS OF A CONVERTER SYSTEM

To analyse the performance of the power electronic converter , a unbalanced ac source is introduced firstly   .the distorted three phase ac voltage is shown in fig.3 ,the phasor diagram ,assumed that the phase B fault occurred with voltage dip on the phase A of the ac source.

According to [2] and [19], any distorted three-phase voltage can be expressed by the sum of components in the positive sequence, negative sequence, and zero sequence. For simplicity of analysis, only the components with the fundamental frequency are considered in this paper, however, it is also possible to extend

the analysis to higher order harmonics. The distorted three-phase ac source voltage in Fig. 3 can be represented by

where V +, V −, and V0 are the voltage amplitude in the positive, negative, and zero sequence, respectively. And ϕ+, ϕ−, and ϕ0 represent the initial phase angles in the positive sequence, negative sequence, and zero sequence, respectively. The predefined voltage dip as indicated in

 Fig. 3 should contain voltage components in all the three sequences [2], [11].

Because there are only three wires and a common neutral point in the windings of the ac source, the currents flowing in the three phases do not contain zero-sequence components. As a result, the three-phase load current controlled by the converter can be written as

With the voltage of the ac source in (1) and the current controlled by the converter in (2), the instantaneous real power p and the imaginary power q in αβ coordinate, as well as the real power p0 in the zero coordinate can be calculated .

Negative feedback in a closed-loop control system DOES NOT_____

1. Negative feedback in a closed-loop control system DOES NOT-----
(A) reduce the overall gain
(B) reduce bandwidth
(C) improve disturbance rejection
(D) reduce sensitivity to parameter
variation

EE gate paper answer KEY -2016

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