dc motor speed controller by pwm technique
TRANSCRIPT
FACULTY OF ENGINEERING(INDUSTRIAL ELECTRONIC AND CONTROL)
DC Motor Speed Controllerby PWM technique
KGK 1500011Khairi A. M. Elrmali
outline• Introduction to pwm technique• Generate PWM signal in MATLAB Simulink
1. Varying Frequency modulation ratio2. varying amplitude modulation ratio
• PWM Spectral Modelling and Characteristics Bipolar Double-Edge Modulation &single-Edge Modulation unipolar Double-Edge Modulation & single-Edge Modulation
• DC motor speed control circuit– switch charactristic
• simulate model by proteus8• Pulse Width Modulator Motor Speed Control kit• CONCLUSION
Introduction to pwm technique• PWM (Pulse Width Modulation) is an efficient way to
vary the speed and power of electric DC motors.
Period (T)
Duty Cycle (D)VL
VH
On Off
%100Period
TimeOnCycleDuty
LHavg VDVDV 1
Duty Cycle is determined by:
Average signal can be found as:
Usually, VL is taken as zero volts for simplicity.
Generate PWM signal in MATLAB Simulink
A.Varying Frequency modulation ratio
sinffm tri
f
The binary PWM output can be mathematically written as
tctrtb pwm sgn
Bipolar& Unipolar pwm genetartor B. varying amplitude modulation ratio
tria V
Vm sin
PWM Spectral Modelling and Characteristics
the harmonic at frequency f = mfc + nf1 is zero if m + n is evenCarrier frequency and its harmonics, at frequencies f = mfc, m = 1, 2,...,+∞.Sideband harmonics of the carrier and its harmonics, at frequencies f = mfc +nf1, n = ±1,±2,...,±∞
single single singledouble double double
single , double edge
PWM Spectral Models
Bipolar Double-Edge Modulation Bipolar trailing-edge modulation
more attractive for AC–DC and DC–AC converter application
PWM Spectral Models unipolar single-Edge Modulation unipolar Double-Edge Modulation
DC motor speed control circuit
• “To explain working of the PWM circuit.”• BASIC BLOCK DIAGRAM
As shown in block diagram there are mainly three blocks: Astable Multivibrator, Driving Circuit and dc motor
The Basic Blocks are explained below:
(5) 1
(4) 244.1
(3) 2
(2) 69.0(1) 69.0
21
21
21
2
21
FT
CRRF
RRRR
TTTD
CRTCRRT
OFFON
ON
OFF
ON
• Multivibrator: This block produces square pulses of variable
frequencies. The frequency of output pulse can be varied by changing the value of resistor shown in figure. These pulses are fed to the driving circuit.
• GENERAL formulae for using 555 as
astable multivibrator:
switch charactristic driving Circuit: 1) A theoretically the switching frequency
must be much higher than 1/Ta where Ta = L/R is the electric time constant of the motor.
2) Usually a frequency around 20 kHz is used. This also avoids noise from the motor in the audio range.
3) The maximum output of the 555 IC is 200mA ,this can increased by BD139 transistor up to 1A ,For high current appication other transistor like BD 139,BD679,TIP31,2N3055 ,MOSFET IRF520,IRF540 .
4) the transistor may be become hot during the operation therefor it is essential to use a suitable heatsink
5) A diode, Di, has been added to reroute inductive motor spikes. A 1N914 or 1N4001, 1N4007 is okay for smaller motors, but prefer a 1N5817.
mAII cb 5
5001
min
The desired collector current is 1A
desire a base current of 10mAcalculate R_b as follows:
4401010
6.053
b
bebb I
VVR
simulate model by proteus8
R4
DC 7
Q 3
GN
D1
VC
C8
TR2 TH 6
CV5
U1
555
U1(VCC)
C15nF
R11k
C25nF
D1
1N4148
D2
1N4148
7%
RV1
10k
R2
440
D31N4001
Q1TIP31
• Description:
• 100% brand new and high quality• Control the speed of a DC motor with this
controller.• High efficiency, high torque, low heat
generating.• With reverse polarity protection, high
current protection.
• Specification:• Model: CCM6C• Input voltage: 6V/12V /24V DC• Control Power: 24V, within 200W; 12V ,
within 200W; 6V , within 60W• Current: Sustained current maximum
20A, suggest use within 10A• PWM Duty Cycle:5% -100%• PWM Frequency:21khz
Pulse Width Modulator Motor Speed Control kit
CONCLUSION
• From the project work, following points can be concluded.
• The motor responds to the average value of the pulses and not to the individual pulses as the chopper works at high frequency.
• Changing the duty-cycle of the pulse by changing the speed of regulator changes the average voltage level.