Lab Assignment

Sim Power System Block In MATLAB

SIm Power System Block Contains:

ü  Electrical Sources

ü  Elements

ü  Extra Library

Ø  Additional Machines

Ø  Control Blocks

Ø  Discrete Control Blocks

Ø  Discrete Measurement

Ø  Phasor Library

Ø  Three Phase Library

ü  Machines

ü  Measurement

ü  Phasor Element

ü  Power Electronics

Electrical Sources:

It Contains

·         AC Current Source

·         AC Voltage Source

·         Controlled Current Source

·         Controlled Voltage Source

·         DC Voltage Source

·         3 Phase Programmable Voltage Source

·        3 Phase Source

Elements:

It contains

·         Breaker

·         Connection Port

·         Ground

·         Linear Transformer

·         Multi Winding Transformer

·         Mutual Inductance

·         Neutral

·         Parallel RLC branch

·         Parallel RLC Load

·         Series RLC Load

·         Surge Arrestor

·         3 Phase Breaker

Machines:

It contains

·         Asynchronous Machine pu Units

·         Asynchronous Machine SI Units

·         DC Machines

·         Discrete DC Machines

·         Excitation System

·         Synchronous Machine SI Fundamental

Measurements:

It Contains

·         Current Measurement

·         Impedance Measurement

·         Multimeter

·         3 Phase V-I Measurement

·         Voltage Measurement

Phasor Elements:

It Contains

·         Static Var Compensator

Power Electronics:

It contains

·         Detailed Thyristor

·         Diode

·         Ideal Switch

·         IGBT

·         MOSFET

·         3 Level Bridge

·         Thyristor

·         Universal Bridge

Basic Power Electronics

Lab report # 08

Phase and Power Control using Diac and Triac

Apparatus:

·         Diac

·         Triac

·         Resistor

·         Potentiometer

·         Capacitor

·         Voltage Source (AC)

·         Oscilloscope

Circuit Diagram:

Procedure:

As the AC supply voltage increases at the beginning of the cycle, capacitor, C is charged through the series combination of the fixed resistor, R1 and the potentiometer, VR1 and the voltage across its plates increases. When the charging voltage reaches the breakover voltage of the diac (about 30 V), the diac breaks down and the capacitor discharges through the diac, producing a sudden pulse of current, which fires the triac into conduction. The phase angle at which the triac is triggered can be varied using VR1, which controls the charging rate of the capacitor.

Once the triac has been fired into conduction, it is maintained in its “ON” state by the load current flowing through it, while the voltage across the resistor–capacitor combination is limited by the “ON” voltage of the triac and is maintained until the end of the present half-cycle of the AC supply.

At the end of the half cycle the supply voltage falls to zero, reducing the current through the triac below its holding current, IH turning it “OFF” and the diac stops conduction. The supply voltage then enters its next half-cycle, the capacitor voltage again begins to rise (this time in the opposite direction) and the cycle of firing the triac repeats over again.

Calculations:

I_T= 0.2mA

I_D= 0.1mA

Basic Power Electronics Lab Report # 07

Phase and Power Control Using SCR:

A silicon controlled rectifier (SCR) is a solid state switching device which can provide fast, infinitely variable proportional control of electric power. Not only does this give maximum control of your heat process, but it can extend heater life many times over other control methods. Since the SCR is solid state, it can cycle on and off over a billion times

In ac circuits the SCR can be turned-on by the gate at any angle α with respect to applied voltage. This angle α is called the firing angle and power control is obtained by varying the firing angle. This is known as phase control. A simple half-wave circuit is shown in figure a. for illustrating the principle of phase control for an inductive load. The load current, load voltage and supply voltage waveforms are shown in figure b. The SCR will turn-off by natural commutation when the current becomes zero. Angle β is known as the conduction angle. By varying the firing angle a, the rms value of the load voltage can be varied. The power consumed by the load decreases with the increase in firing angle a. The reactive power input from the supply increases with the increase in firing angle. The load current wave-form can be improved by connecting a free-wheeling diode D1, as shown by the dotted line in fig-a. With this diode, SCR will be turned-off as soon as the input voltage polarity reverses. After that, the load current will free wheel through the diode and a reverse voltage will appear across the SCR. The main advantage of phase control is that the load current passes through a natural zero point during every half cycle. So, the device turns-off by itself at the end of every conducting period and no other commutating circuit is required