Microprocessor Controlled Ac and Dc Drives Ppt

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Text of Microprocessor Controlled Ac and Dc Drives Ppt

Presented By Md Manzar Nezami Md Mustafa kamal

A microprocessor is an electronic device that consists of millions (or billions) of transistors packed into one IC. Its function is to execute instructions in the form of programs, calculate and store its results. Microprocessors are used widely in our everyday lives.

P is a complex, powerful device: Able to process huge amounts of data. Built using transistors etched on silicon die. Needs external components to support operation.

Microcomputer system support P operations.

The microprocessor can be used to perform complex operations by giving it instructions. These instructions are called programs. Programs are loaded into memory, and are executed line-by line by the microprocessor.

Definition: A complete electronic system built around the microprocessor to support the microprocessor operation. May consist of CPU, memory, I/O (disk drives, keyboard, mouse), system bus, and supporting circuitry. CPU as the brain controls actions of all components.






Supporting Circuitry





Power Supply


LCD Display


A P-based system consists of many components: CPU. Memory. I/O: disk drives, keyboard, mouse. System Bus. Supporting circuitry.

All components communicate using System Bus.

Parallel I/O

Serial I/O

Interrupt Circuit

System Bus





Master of all components. Job: Get instructions from memory. Execute instructions. Perform calculations (may use math co-processor). Control bus operations.

CPU consists of: ALU (Arithmetic/Logic Unit): Performs arithmetic/ logic computations.

CU (Control Unit): Responsible to retrieve instructions, analyze, then execute.

Registers: Fast internal storage. Used to temporarily store addresses, data, processor status.


Stores instructions and data for CPU. Each memory location given unique address. CPU refers to address to access.

Types: Read-Only Memory (ROM). Random-Access Memory (RAM). Non-Volatile Memory (NVM).


Synchronizes all components in the system. All components refer to the clock timing for operations.

Generates square waves at constant intervals. Crystal oscillator + timing circuitry. Higher clock speed allow computers to function faster.

Input/Output. Connects P with external devices: Add functionality to P.

Interfaces with P using ports. Examples: Keyboard. Mouse. Display monitor.

Built into board Using card slots.

An electric motor together with its control equipment and energy transmitting device forms an Electric Drives. Some examples of electricdrive systems are: A ceiling fan motor with regulator and also with blades, a food mixer with food to be processed, a motor and conveyer belt with material on its belt and so on. Electric drives are mainly two types:DC Drives AC drives

AC drives are those in which motive power provided by ac motors. Though speed control of dc motors is easy as compared to ac motors, but ac motors have some advantages which outweighed the advantages of dc motors, and so with the development of different techniques of speed control of ac motor drives, now days, ac motor drives are more extensively use in industries.

Low maintenance cost. AC drives have a better power factor in most applications. Harmonics reduction is cheaper in case of AC drives. Higher transient response capability. AC drives are of lower cost in comparison to DC drives.

High braking cost. Complex braking strategy. Complex and expensive technique. Problem of switching losses. High insulation cost.



Two types of controlling

Hardwire control Electronic control/digital control

Small size Fast response Less power consumption Accurate and efficient Controlling range increased System reliability is much more than conventional one. economical

Control of 4-quadrant micro computer controlled dc drive system


3-phase AC SupplyLine synchronizing circuit

Thyristor to be triggred

Current control

Firing angle Evaluation Timer And logic

Pulse Amplifier

Current comparator

Four quadrant logic


Speed Control


Motor Current Speed Signal

Speed ComparatorRefrence speed




start Initialization Start comman no d? yes Read reference speed Read motor speed Calculate speed error & current reference Torque reversal ? yes no no Stop sequence Changeover sequence

stop Comman d? yes

Read motor current Compute current error Compute firing angle & output firing signal



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