POWER ELECTRONICS
PROJECT REPORT
DC MOTOR CONTROL USING THYRISTOR
“Project Report”
SUBJECT:
Power electronics (ES-329)
TOPIC:
“DC Motor Control using Thyristor”
SUBMITTED BY:
• Areesha Ikhtiar (19MTE01)
• Dur E shahwar (19MTE03)
• Priyanka Rathi (19MTE16)
SUBMITTED TO:
• Engr. Qurban Memon
SUBMISSION DATE:
09/12/22
CONTENTS:
1. Abstract.
2. Introduction.
3. Required Components.
• Description of Components
4. Connections.
5. Working Principle of Circuit.
6. Circuit Diagram and Simulation Result.
7. Advantages and Disadvantages.
8. Applications.
9. Conclusion.
ABSTRACT
The versatile control characteristics of DC motors have contributed to the extensive use of DC
motors in the industry. With the increasing use of power semiconductors, the speed control of
motors increasingly getting sophisticated and precise. Speed of the speed dc motor is controlled
by controlling the armature voltage. Armature voltage is controlled using different single-phase
AC/DC converter. Half converter, semi-converter, full converter, and dual Converter are some of
the thyristor-based circuits which are used for speed control of DC thyristors. This project studies
different speed control techniques of DC motors and makes a comparative study of different
converter-based speed controller techniques.
INTRODUCTION
DC motors are widely used in industry because of their low cost, less complex control structure,
and wide range of speed and torque. There are many methods of speed control of DC drives namely
field control, armature voltage control, and armature resistance control methods. DC motors
provide high starting torque which is required for traction applications. In DC motor control over
a large speed range, both below and above the rated speed can be achieved quite easily. DC motors
have inherent disadvantages that it needs regular maintenance and it is bulky in size. DC motors
are tailor made, so it is very difficult to replace them.
In general, the armature voltage control method is widely used to control the DC drives. In this, a
controlled rectifier, or chopper is used but due to element of power electronics elements, nonlinear
torque-speed characteristics are observed which are undesirable for control performance.
Nowadays state of art speed control techniques of DC motors is available. Thyristor-based DC
drives with analog and digital feedback control schemes are used. Phase locked loop control
technique is also used for precise speed control and zero speed regulation. In past, many
researchers presented various new converter topologies of DC motor control for different
applications of industry, but at the basic level in all of them, thyristor-based AC-DC converter are
used. PSPICE with its toolbox converters like Simulink and SimPowerSystem is used for
simulation.
COMPONENTS REQUIREMENT
The components required to design this project are:
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9v DC supply
Thyristor (TYN612)
DC motor
Resistor (510 ohm and 1k ohm)
Switch
Push button
Connecting wires
COMPONENTS DESCRIPTION
Description of respective electronic components:
1. 9v DC supply:
This 9V 2A DC Power Adapter This 9V 2A DC Power Adapter is
a high-quality power supply manufactured specifically for
electronics. These are switch mode power supplies which means
the output is regulated to 9V and the capable output current is much
higher (2000mA). Specification: Voltage Input: AC 100-240V.
2. Thyristor (TYN612):
A thyristor is a switching device that can be used in the power control
circuit, over-voltage protection, and many others application. It requires a
gate pulse to start, it gets self-latched and stays ON until the supply gets
interrupted.
3. DC motor:
A DC motor is defined as a class of electrical motors that convert direct
current electrical energy into mechanical energy.
4. Resistor:
A resistor is an electrical component that limits or regulates the flow of
electrical current in an electronic circuit. Resistors can also be used to
provide a specific voltage for an active device such as a transistor.
5. Push button:
A Push Button switch is a type of switch which consists of a simple electric
mechanism or air switch mechanism to turn something on or off.
Depending on the model they could operate with momentary or latching
action functions. The button itself is usually constructed of a strong
durable material such as metal or plastic.
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CONNECTIONS
Place the Thyristor on the breadboard and connect the cathode terminal to ground.
Connect one terminal of the DC motor to the Anode terminal of the thyristor and the other
terminal to the switch.
Connect the gate terminal of the thyristor to the resistor and push the button, as shown in
the circuit diagram.
To test the circuit, connect the battery and close the switch S1. When you want to start the
motor press the push button and to turn off the motor, open the switch S1.
WORKING OF CONTROLLING DC MOTOR USING THYRISTOR CIRCUIT
Thyristors are semiconductor devices designed for high-power switching applications. Like
Thyristors, transistors are also used as switching device. Transistors are the tiny electronic
component that changed the world, we can find them in every device like TVs, mobiles, laptops,
calculators, earphones, etc.
Initially, the switches S1 and S2 remain in normally closed and normally-open states respectively.
When the supply is ON, Thyristor remains reversed biased until the gate pulse is provided. For
providing gate pulse we have to use Push Button S2. As the S2 switch close, SCR turns ON and
latches even we release the pushbutton S2.
When the Thyristor has self-latched into the ON state, the only way to stop the Thyristor from
conducting is to interrupt the power supply. For that, we use switch S1, which cuts the power
supply of the circuit and the Thyristor gets reset or turns OFF.
Resistance R1 is used to provide sufficient gate current to turn ON the SCR. Resistance R2 is used
for decreasing the gate sensitivity and increasing the dv/dt capability. Therefore, it prevents
Thyristor from false triggering.
SCR ADVANTAGES AND LIMITATIONS
ADVANTAGES
It can handle large voltages, currents and power.
The voltage drop across conducting SCR is small,
thus, reducing the power dissipation in SCR.
LIMITATIONS
It can conduct only in one direction. So it can
control power only during one half cycle of ac.
It can turn on accidentally due to high dv/dt of
the source voltage.
Easy to turn on and we can control the power
delivered to the load.
It is not easy to turn off the conducting SCR. We
have to use special circuits called commutation
circuits to turn off a conducting SCR.
Triggering circuits are simple.
SCR cannot be used at high frequencies. The
maximum frequency of its operation is 400 Hz.
It can be protected with the help of a fuse.
Gate current cannot be negative.
CIRCUIT DIAGRAM & SIMULATION RESULT
The circuit designing and simulation of circuit is done with the help of Proteus 8 software. First
figure represents the circuit connection of SCR controlled DC motor while the next figure presents
the simulation.
APPLICATIONS
The silicon controlled rectifier (SCR) circuits can be used:
• In light dimmers
• To control the speed of the motors.
• In AC voltage stabilizers.
• In switch.
• In choppers.
• In inverters.
• For DC circuit breaker.
• In battery charger.
• It is used for AC power control with solid relay.
CONCLUSION
Thyristor switching circuits can be used to control much larger loads such as lamps, motors,
heaters, etc. This report explains how to control a DC motor by using a thyristor TYN612. Motor
rotation control system with SCR using a DC voltage supply, the motor will rotate only when S1
is triggered. Increasing variable voltage give the current increase thus DC motor rotation faster.
Furthermore, DC motor control uses AC voltage supply, the less current flow causes rotation of
the motor to slow.