This document discusses the digital control of DC drives using microcomputers. It describes how microcomputers can be used to control the speed and current of DC motors through programs that implement constant torque and constant horsepower operations. The microcomputer provides reliable control, flexibility to change control strategies, and can incorporate additional features like diagnostics and protections. Microcomputers reduce costs and size compared to analog controls while improving control performance and reliability. Speed is detected and current sensed to provide feedback for the inner current and speed control loops implemented through the microcomputer.

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Dr. A. Ravi
Professor/EEE
FRANCIS XAVIER ENGINEERING COLLEGE
TIRUNELVELI
DIGITAL CONTROL OF
DC DRIVE

2. • Phase Locked Loop and micro-computer
control of DC drives
•Program flow chart for Constant torque
•Program flow chart for constant horse power
operations
•Speed detection and Current sensing circuits
and feedback elements.
Overview
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3. MICRO-COMPUTER CONTROL OF
DC DRIVES
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4.  Microcomputer, an electronic device with a microprocessor
as its central processing unit (CPU).
 Microprocessor- The microprocessor is also a general-purpose
processor that consists of a control unit, ALU, a bunch of registers
also called scratchpad registers, control registers and status
registers.
 Microcontroller - Microchip Atmega328-AU, Microchip
P1C16F877A-I/P, Microchip P1C16F1503-I/P, Microchip
P1C16F671-I/SN, Microchip P1C18F45K22-I/P, etc.
 Embedded Processor- It consists of several blocks they are the
processor, timer, an interrupt controller, program memory and data
memory, power supply, reset and clock oscillator circuits, system
application-specific circuits, ports and interfacing circuits.
 Digital Signal Processor- T1 C5416, DSP 32C Processor
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Micro Computer

5.  Reduces costs and Size
 Provides Reliability and Control Performance
 Flexible to change the control strategy
 Extra Features can be added to meet performance
parameters.
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Advantages of Microcomputer Based DC Motor Drive

6.  Speed Control
 Current Control
 Start and Stop of drive
 Diagnostics for built-in fault finding
 Protections
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Performs various desirable functions such as

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MICRO COMPUTER BASED MOTOR SPEED CONTROL

8. FEATURES OF MICRO COMPUTER BASED CONTROL
 Speed Signal is fed by use of D/A converter
 An inner current –control loop is used to control the
armature current
 Line Synchronizing Circuit - To Synchronize the
generation of the firing pulses with the supply line
frequency.
 Pulse amplifier-- Provides the necessary isolation and
produces the gate pulses of required magnitude and
duration.
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10.  The main function of the microprocessor is generating the
firing pulses with least possible asymmetry.
 The accuracy in the calculation of current and speed loops.
The sampling periods of these loops are however larger than
those of the generating pulses. The error in computation must
be limited.
 If extra accuracy is required in the speed loop the
microprocessor must be capable of floating point arithmetic in
order to handle large numbers. For this purpose a fast
microprocessor with optimised programs may be required.
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SELECTION OF A CONTROL OF DC DRIVE USING MICROPROCESSORS

11.  chopper controlled four quadrant dc drives
using separately excited dc motor or dc series
motor.
 multiphase chopper controlled dc drives
 pulse width controlled dc drives
 The multiple firing schemes for improving the
performance of dc drives, g., TRC and CLC.
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APPLICATIONS OF MICROPROCESSORS IN THE AREA OF DC
DRIVES

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MICRO PROCESSOR MOTOR SPEED CONTROL

13. MICRO-COMPUTER CONTROL OF DC DRIVES
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