MAHARANA PRATAP ENGINEERING COLLEGE

AFFILIATED TO

APJAKTU LUCKNOW( UP)

MINOR PROJECT REPORT

ON

“THREE PHASE FULL WAVE RECTIFIER”

Submitted to: Submitted by:

DEPORTMENT OF VINAY SINGH

ELECTRICAL ENGINEERING ROLL NO- 1404620904

B.Tech 3rd YEAR

Session 2015-2016

INDEX;

1. CERTIFICATE

2. ACKNOWLEDGEMENT

3. ABSTRACT

4. INTRODUCTION

5. CIRCUIT DIAGRAM

6.CIRCUIT DESCRIPTION

7. WORKING

8. SIMULINK MODEL

9. SIMULINK BLOCK DESCRIPITION

10. ADVANTAGE AND DISADVANTAGE

11. APPLICATION

12. REFERENCE

CERTIFICATE

This is to certify that VINAY SINGH, a student of ELECTRICAL

ENGINEERING , B.TECH 3rd year has successfully completed the project

titled “THREE PHASE FULL WAVE RECTIFIER” under the guidance of

Mr. DHARMENDRA UPADDHAYA. During the academic year 2015-16 in

mini project examination conducted by”A.P.J.ABDUL KALAM

UNIVERCITY LUCKHNOW”.

Signature of external Signature of guide

Examiner: teacher:

ACKNOWLEDGEMENT

In the accomplishment of this project successfully, many people have best owned upon me their

blessings and the heart pledged support, this time I am utilizing to thank all the people who have been

concerned with project.

Primarily I would thank god for being able to complete this project with success. Then I would like to

thank my project guide Mr. DHARMENDRA UPADDHAYA and Mr. PUSHPANDRA SINGH, whose

valuable guidance has been the ones that helped me patch this project and make it full proof success his

suggestions and his instructions has served as the major contributor towards the completion of the

project.

Then I would like to thank my parents and friends who have helped me with their valuable suggestions

and guidance has been helpful in various phases of the completion of the project.

SIGNATURE;

HOD OF ELECTRICAL ENGG.

Mrs. Lovi kaushal

ABSTRACT

In particle accelerators, rectifiers are used to convert the AC voltage into DC or low-frequency AC to

supply loads like magnets or klystrons. Some loads require high currents, others high voltages, and

others both high current and high voltage. This presentation deals with the particular class of line

commutated rectifiers (the switching techniques are treated elsewhere). The basic principles of

rectification are presented. The effects of real world parameters are then taken into consideration. Some

aspects related to the filtering of the harmonics both on the DC side and on the AC side are presented.

Some protection issues associated with the use of thyristors and diodes are also treated. An example of

power converter design, referring to a currently operating magnet power supply, is included. An

extended bibliography (including some internet links) ends this presentation.

3. INTRODUCTION

A rectifier is an electrical device that converts alternating current (AC), which periodically reverses

direction, to direct current (DC), which flows in only one direction. The process is known as

rectification.

Rectification produces a type of DC that encompasses active voltages and currents, which are then

adjusted into a type of constant voltage DC, although this varies depending on the current's end-use.

The current is allowed to flow uninterrupted in one direction, and no current is allowed to flow in the

opposite direction. Physically, rectifiers take a number of forms, including vacuum tube diodes,

mercury-arc valves, copper and selenium oxide rectifiers, semiconductor diodes, silicon-controlled

rectifiers and other silicon-based semiconductor switches.

Rectifier circuits may be single-phase or multi-phase. Most low power rectifiers for domestic equipment

are single-phase, but three-phase rectification is very important for industrial applications and for the

transmission of energy as DC.

Because of their ability to conduct current in one direction, diodes are used in rectifier circuits.

The definition of rectification process is “ the process of converting the alternating voltages and currents

to direct currents and the device is known as rectifier” It is extensively used in charging batteries;

supply DC motors, electrochemical processes and power supply sections of industrial components.

using 6 diodes.

upper diodes d1,d3,d5 constitutes +ve group.

lower diodes d4,d6,d2 constitutes –ve group.

three phase t/f feeding the bridge is connected in delta-star .

INTRODUCTION OF THREE PHASE RECTIFIER

THREE phase diode bridge rectifiers are often used in industry to provide the dc input voltage for

motor drives and dc-to-dc converters.

The main drawback of these rectifiers is that they inject significant current harmonics into the power

network.

These harmonics current injections can detrimentally affect the power system by overloading nearby

shunt capacitors and by distorting the bus voltage at the point of common coupling.

Computation of harmonics is routinely accomplished through use of transient time domain simulation.

While this approach is effective, it is not without challenges. Accuracy of simulation results depends on

simulation time step size and simulation length—quantities that must be estimated based on experience,

or selected using trial and error.

An alternative approach is to employ harmonic domain analysis methods [1], [2]. By avoiding

simulation of circuit transients, these methods yield accurate steady-state harmonic spectra in a more

computationally efficient manner.

Once again, user experience is required to obtain accurate harmonic results, since accuracy depends on

the numbers of harmonics included during the calculation process.

In this paper, a time domain sampled-data model is presented to iteratively solve for the current and

voltage harmonics injected by a three-phase full bridge rectifier with capacitive load.

4. CIRCUIT DIAGRAM

The computation time is short compared to transient time domain simulation because the proposed

method

1) directly calculates the steady-state solution without stepping through system transients;

2) can employ known waveform symmetry.

In contrast to harmonic domain analysis methods, the proposed time domain sampled-data model can

accurately determine harmonics of interest without concern for harmonic truncation error or aliasing

effects.

Section II introduces the circuit descriptions of the rectifier being analyzed.

Sections III and IV show how to use the proposed method to analyze discontinuous conduction modes

(DCM) and continuous conduction mode (CCM).

A computational example is presented in Section V to demonstrate the validity of the method.

5. CIRCUIT DESCRIPTION

Fig. shows a six-pulse capacitor-filtered diode bridge rectifier where the dc load is modeled as an

equivalent resistance R. The line harmonics are filtered by the ac chokes .

This type of rectifier is frequently employed for battery charger application [5]. It is also used for

adjustable speed drives [6] because it has better drive isolation and lower dc current requirements [7],

[8] than a conventional inductor-filtered rectifier.

Surprisingly, as noted in [9], the literature available on comprehensive analysis of this rectifier is quite

limited. In fact, [3] is the only reference which provides complete analytical models for both DCM and

CCM without the aids of transient time domain simulation.

However, the approach in [3] requires evaluation of a lengthy inverse Laplace Transformation, which

becomes complicated for the case of CCM analysis.

The proposed model provides a viable alternative to [3]. DCM and CCM are modeled in an efficient and

unified fashion without the need for inverse Laplace Transformation.

To simplify the model development and discussion, only balanced operation of the converter is

considered. However,

6.WORKING;

A three-phase diode rectifier converts a three-phase AC voltage at the input to a DC voltage at the output. To show the working principle of the circuit the source and load inductances (Ls and Ld) are neglected for simplicity.

The DC voltage is divided into six segments within one fundamental source period that corresponds to the different line-to-line source voltage combinations (VLL). In each segment there is a minimum and maximum DC voltage:

Minimum DC voltage: If one line-to-line voltage is zero, then the DC voltage is at a minimum of VDC = VLL · sin(60°).

Maximum DC voltage: The DC voltage increases up to a maximum of VDC = VLL, where two line-to-line voltages are equal.

In between the minimum and maximum DC voltages lies the average DC voltage that is given by: VDC,av = VLL · 3/pi. The ripple of the DC voltage occurs at 6-times the line frequency. For the six intervals the signs of the phase currents (Ia,Ib,Ic) are given by:

Phase interval Sign of phase currents

0°<φ<60° ( 0,-1, 1)

60°<φ<120° ( 1,-1, 0)

120°<φ<180° ( 1, 0,-1)

180°<φ<240° ( 0, 1,-1)

240°<φ<300° (-0, 1, 0)

300°<φ<360° (-1, 0, 1)

OUTPUT WAVE FORM;

CONDUCTION OF DIODE;

D3 D1 D2 D3

Variation of voltage across Diode D1;

Voltage variation across diode D1 can be obtained by applying KVL to the loop consisiting of diode D1,

Phase ‘a’ winding and load R.

So, -VD1 -Vo + Va = 0 or VD1 = Va – Vo

When Diode D1 conduct:

Vo = Va

Therefore , VD1 = Va – Va = 0

When diode D2 conduct:

Therefore , VD1 = Va – Vb

At ᾠt = 180 , Vb=0.866 Vmp , Va = 0 VD1 = - 0.866 Vmp⁰

At ᾠt = 210 , Vb= Vmp , Va = -0.5 Vmp VD1 = -1.5 Vmp⁰

At ᾠt = 240 , Vb=0.866 Vmp , Va = 0.866 Vmp VD1 = - √3 Vmp⁰

At ᾠt = 270 , Vb=0.5 Vmp , Va = - Vmp VD1 = -1.5 Vmp⁰

When Diode D3 conducts :

VD1 = Va - Vc At ᾠt = 300 ,⁰

Va=-0.866 Vmp , Vc = 0.866Vmp

VD1 = - √3 Vmp At ᾠt = 330 , ⁰

Va=-0.5 Vmp ,

Vc = Vmp VD1 = - 1.5 Vmp

At ᾠt = 360 , Va=0,⁰

Vc = 0.866Vmp VD1 = -0.866 Vmp

At ᾠt = 390 , Va= 0.5 Vmp ,⁰

Vc = 0.5Vmp VD1 = 0

EQUATIONS OF PHASE VOLTAGES FROM

WHERE ABOVE VALUES ARE OBTAINED

Va = Vmp sin (ᾠt),

Vb = Vmp sin(ᾠt – 120 ),⁰

Vc = Vmp sin(ᾠt – 240 )⁰

SIMULINK MODEL OF FULL WAVE RECIFIER:

OUTPUT WAVE FORM OF SIMULINK MODEL

SIMULINK BLOCK DESCRIPTION

DIODE

The diode is a semiconductor device that is controlled by its own voltage Vak and current Iak. When a diode is forward biased (Vak > 0), it starts to conduct with a small forward voltage Vf across it. It turns off when the current flow into the device becomes 0. When the diode is reverse biased (Vak < 0), it stays in the off state.

The Diode block is simulated by a resistor, an inductor, and a DC voltage source connected in series with a switch. The switch operation is controlled by the voltage Vak and the current Iak.

The Diode block also contains a series Rs-Cs snubber circuit that can be connected in parallel with the diode device (between nodes A and K).

AC VOLTAGE SOURCE

Implement sinusoidal voltage source

The AC Voltage Source block implements an ideal AC voltage source. The generated voltage U is described by the following relationship.

Negative values are allowed for amplitude and phase. A frequency of 0 and phase equal to 90 degrees specify a DC voltage source. Negative frequency is not allowed; otherwise the software signals an error, and the block displays a question mark in the block icon.

DIALOG BOX AND PARAMETERS

Peak amplitude

The peak amplitude of the generated voltage, in volts (V).

PhaseThe phase in degrees (deg).FrequencyThe source frequency in hertz (Hz).

Sample timeThe sample period in seconds (s). The default is 0, corresponding to a continuous source.

MEASUREMENTSSelect Voltage to measure the voltage across the terminals of the AC Voltage Source block. Place a Multimeter block in your model to display the selected measurements during the simulation. In the Available Measurements list box of the Multimeter block, the measurement is identified by a label followed by the block name.

Measurement Label

Voltage Usrc:

VOLTAGE MEASUREMENT

The Voltage Measurement block measures the instantaneous voltage between two electric nodes. The output provides a Simulink signal that can be used by other Simulink blocks.

Dialog Box and Parameters

OUTPUT SIGNAL

Specifies the format of the output signal when the block is used in a phasor simulation. The Output signal parameter is disabled when the block is not used in a phasor simulation. The phasor simulation is activated by a Powergui block placed in the model.

Set to Complex to output the measured current as a complex value. The output is a complex signal.

Set to Real-Imag to output the real and imaginary parts of the measured current. The output is a vector of two elements.

Set to Magnitude-Angle to output the magnitude and angle of the measured current. The output is a vector of two elements.

Set to Magnitude to output the magnitude of the measured current. The output is a scalar value.

MUX

The Mux block combines its inputs into a single vector output. An input can be a scalar or vector signal. All inputs must be of the same data type and numeric type. The elements of the vector output signal take their order from the top to bottom, or left to right, input port signals. See How to Rotate a Block for a description of the port order for various block orientations. To avoid adding clutter to a model, Simulink hides the name of a Mux block when you copy it from the Simulink library to a model. See Mux Signals for information about creating and decomposing vectors.

Note The Mux block allows you to connect signals of differing data and numeric types and matrix signals to its inputs. In this case, the Mux block acts like a Bus Creator block and outputs a bus signal rather than a vector. The MathWorks discourages using Mux blocks to create bus signals, and might not support this practice in future releases. See Avoiding Mux/Bus Mixtures for more information.

Use the Number of inputs parameter to specify input signal names and sizes as well as the number of inputs.

Specifies the number of inputs to the Mux block.

When you use this format, the block accepts scalar or vector signals of any size. Simulink assigns each input the name signalN, where N is the input port number.

VECTOR

The length of the vector specifies the number of inputs. Each element specifies the size of the corresponding input.

A positive value specifies that the corresponding port can accept only vectors of that size.

CELL ARRAY

The length of the cell array specifies the number of inputs. The value of each cell specifies the size of the corresponding input.

A scalar value N specifies a vector of size N. A value of -1 means that the corresponding port can accept scalar or vector signals of any size.

SIGNAL NAME LIST

You can enter a list of signal names separated by commas. Simulink assigns each name to the corresponding port and signal. For example, if you enter position,velocity, the Mux block will have two inputs, named position and velocity.

The MathWorks encourages using Vector Concatenate blocks rather than Mux blocks to combine vectors. The primary exception is the creation of a vector of function calls, which requires a Mux block. In future releases, Mux blocks might have no unique capabilities and might be deprecated.

If you want to create a composite signal, in which the constituent signals retain their identities and can have different data types, use a Bus Creator block rather than a Mux block. Although you can use a Mux block to create a composite signal, The MathWorks discourages this practice. See Avoiding Mux/Bus Mixtures for more information.

DATA TYPE SUPPORT

The Mux block accepts real or complex signals of any data type that Simulink supports, including fixed-point and enumerated data types.

For more information, see Data Types Supported by Simulink in the Simulink documentation.

DEMUX

The Demux block extracts the components of an input signal and outputs the as separate signals. The output signals are ordered from top to bottom output port. See How to Rotate a Block for a description of the port order for various block orientations. To avoid adding clutter to a model, Simulink software hides the name of a Demux block when you copy it from the Simulink library to a model. See Mux Signals for information about creating and decomposing vectors.

The Number of outputs parameter allows you to specify the number and, optionally, the dimensionality of each output port. If you do not specify the dimensionality of the outputs, the block determines the dimensionality of the outputs for you.

The Demux block operates in either vector mode or bus selection mode, depending on whether you selected the Bus selection mode parameter. The two modes differ in the types of signals they accept. Vector mode accepts only a vector-like signal, that is, either a scalar (one-element array), vector (1-D

array), or a column or row vector (one row or one column 2-D array). Bus selection mode accepts only a bus signal.

Note The MathWorks discourages enabling Bus selection mode and using a Demux block to extract elements of a bus signal. Muxes and buses should not be intermixed in new models. See Avoiding Mux/Bus Mixtures for more information.

The Demux block's Number of outputs parameter determines the number and dimensionality of the block's outputs, depending on the mode in which the block operates.

CURRENT MEASUREMENT

The Current Measurement block is used to measure the instantaneous current flowing in any electrical block or connection line. The Simulink output provides a Simulink signal that can be used by other Simulink blocks.

OUTPUT SIGNAL

Specifies the format of the output signal when the block is used in a phasor simulation. The Output signal parameter is disabled when the block is not used in a phasor simulation. The phasor simulation is activated by a Powergui block placed in the model.

Set to Complex to output the measured current as a complex value. The output is a complex signal.

Set to Real-Imag to output the real and imaginary parts of the measured current. The output is a vector of two elements.

Set to Magnitude-Angle to output the magnitude and angle of the measured current. The output is a vector of two elements.

Set to Magnitude to output the magnitude of the measured current. The output is a scalar value.

SCOPE

The Scope block displays its input with respect to simulation time.

The Scope block can have multiple axes (one per port) and all axes have a common time range with independent y-axes. The Scope block allows you to adjust the amount of time and the range of input values displayed. You can move and resize the Scope window and you can modify the Scope's parameter values during the simulation.

The Scope Block described here is not the same as the Scope Viewer. For help on the scope viewer, see Things to Know When Using Viewers.

When you start a simulation the Scope windows are not opened, but data is written to connected Scopes. As a result, if you open a Scope after a simulation, the Scope's input signal or signals will be displayed.

If the signal is continuous, the Scope produces a point-to-point plot. If the signal is discrete, the Scope produces a stair-step plot.

Note By default, the Scope block only displays major time step values. However, if a variable-step solver is employed and if the Refine parameter is set to a value greater than 1, minor (intermediate) time step values are displayed in direct proportion to the Refine setting.

The Scope provides toolbar buttons that enable you to zoom in on displayed data, display all the data input to the Scope, preserve axis settings from one simulation to the next, limit data displayed, and save data to the workspace. The toolbar buttons are labeled in this figure, which shows the Scope window as it appears when you open a Scope block.

ADVANTAGES OF FULL WAVE RECTIFIER;

1.Efficiency is higher.

2. The large dc power output.

3.The ripple factor is less.

4. Converters are simple & less expensive & the efficiency of full wave converter is high.

5. The ripple voltage is low &of higher frequency in case of full wave converter so simple filtering circuit

is required.

6. Higher output voltage ,higher output power & higher transformer utilization factor (TUF) in case of full

wave converter.

7. In a full wave converter, there is no problem due to DC saturation of the core because the dc current in

the two halves of the two halves of the transfor mer secondry flow in opposite direction.

8. No centre tap is required in the transformer secondry so in case of bridge converter the transformer

required simpler.

DISADVANTAGES OF FULL WAVE RECTIFIER;

1.PIV rating of diode is higher.

2.Higher PIV diodes are larger in size and costlier.

3.The cost of center tap transformer is high.

APPLICATION;

1 .The primary application of rectifiers is to derive DC power from an AC supply (AC to DC converter).

2. Virtually all electronic devices require DC, so rectifiers are used inside the power supplies of virtually

all electronic equipment.

3. Converting DC power from one voltage to another is much more complicated. One method of DC-to-

DC conversion first converts power to AC (using a device called an inverter), then uses a transformer to

change the voltage, and finally rectifies power back to DC.

4. A frequency of typically several tens of kilohertz is used, as this requires much smaller inductance

than at lower frequencies and obviates the use of heavy, bulky, and expensive iron-cored units.

5. Rectifiers are also used for detection of amplitude modulated radio signals.

6. The signal may be amplified before detection. If not, a very low voltage drop diode or a diode

biased with a fixed voltage must be used.

7. When using a rectifier for demodulation the capacitor and load resistance must be carefully matched:

too low a capacitance makes the high frequency carrier pass to the output, and too high makes the

capacitor just charge and stay charged.

8. Rectifiers supply polarised voltage for welding.

9. In such circuits control of the output current is required; this is sometimes achieved by replacing

some of the diodes in a bridge rectifier with thyristors, effectively diodes whose voltage output can be

regulated by switching on and off with phase fired controllers.

10. Thyristors are used in various classes of railway rolling stock systems so that fine control of the

traction motors can be achieved. Gate turn-off thyristors are used to produce alternating current from a

DC supply, for example on the Eurostar Trains to power the three-phase traction motors.

REFERENCES

1) “Power Electronics” P.C.Sen; Tata McGraw-Hill 1995

2) “Power Electronics; Circuits, Devices and Applications”, Second Edition, Muhammad H.Rashid; Prentice-Hall of India; 1994.

3) “Power Electronics; Converters, Applications and Design” Third Edition, Mohan, Undeland, Robbins, John Wileys and Sons Inc, 2003.

4) A. Lytel (1975). “Silicon Controlled Rectifiers”. Howard W.Sams & Co., Inc:New York.

5)Wikipedia Website, The Free Encyclopedia, Silicon-Controlled RectifierArticle, http://www.wikipedia.org.