Some Practical Design Aspects of a Microcontroller Based Unit for ...

Some Practical Design Aspects of a Microcontroller
Based Unit for AC Motor Control
Mario Makraduli FEIT Skopje

TYPICAL CONSTRUCTION OF AN AC MOTOR

TORQUE – SLIP DEPENDENCE

TYPICAL APPLICATION OF A DRIVE SYSTEM

GENERATION OF MODULATED DRIVE SIGNALS

V/Hz CONTROL WITHOUT FEEDBACK

POWER SAVINGS WITH V/Hz SYSTEMS

BLOCK DIAGRAM OF VECTOR CONTROL SYSTEMS

CLARKE TRANSFORMATION

PARK TRANSFORMATION

PWM DRIVE SECTION

GENERATION OF STATE VECTORS

STATE VECTOR AND VOLTAGE PROJECTIONS

SECTOR VERSUS STATE VECTOR DEPENDENCE

OVERVIEW OF THE SYSTEM

PSU SECTION

CONTROLLER SECTION

VOLTAGE AND CURRENT WAVEFORMS

CURRENT ASSOCIATED WITH SPEEDUP

DEMONSTRATION OF OPERATION

DESCRIPTION OF ONE PROBLEM
• WHEN THE ROTATION SPEED IS TO BE MEASURED
BY MEANS OF ENCODER, THE ACTUAL SPEED
POUSES CERTAIN PROBLEMS
• REGARDING ANGULAR SPEED TWO APPROACHES
ARE COMMON
• MEASUREMENT OF THE TIME INTERVAL BETWEEN
TWO CONSECUTIVE PULSES GENERATED BY THE
ENCODER
• COUNTING THE NUMBER OF REFERENT PULSES
BETWEEN THE TWO CONSECUTIVE PULSES
GENERETED BY THE ENCODER

AVAILABLE RESOURCES IN THE SYSTEM
• THE SYSTEM IS BASED ON DSC CONTROLLER
MC56F8322

PERIPHERIAL UNITS WITHIN THE
MICROCONTROLLER

TYPICAL TIME DIAGRAMS ASSOCIATD WITH
APPLICATION OF QUADRATURE ENCODER

OVERVIEW OF THE MEASUREMENT SYSTEM

NUMBER OF PULSES REGISTERED WITH
THE FIRST APPROACH
N Q = 4N L vT W = 1,1182 v
* Tw is the duration of the PWM cycle
v(rot/s) 1 10 100
N Q
1 11 111
Er (%)
100
9.1
0.9

RESULTS OBTAINED WITH THE SECOND APPROACH
v =
2π 60 10 6
1024 8 N1
=
46019
N 1
rad
s
=
7324
N 1
rot
s
v(rot/s) 1 10 100
N 1
7324 732 73
Er (%)
0.013
0.13
1.37

COMPARIOSON OF THE MEASURED AND REFERENT
RESULTS
f
(Hz)
N1
(pls)
Er1
(%)
v mer
(RPM)
Er2
(%)
1001
7489
-0.047
60
3.448
2002
3746
-0.007
116
-0.855
5004
1498
-0.053
292
-0.341
10003
749
-0.103
585
-0.171
20026
374
-0.137
1171
-0.340
50053
149
-0.561
2929
-0.678
100038
74
-1.296
5859
-1.330
f frequency of the signal generated by the function
generator
N1 number of counted pulses,
Er1 and Er2 errors obtained by both methods

RESULTS PRESENTED ON THE DISPLAY UNIT BY
MEANS OF DEDICATED SOFTWARE
f
(Hz)
1002
2001
5010
10021
20015
50108
100220
N1
(pls)
7485
3747
1497
748
375
149
75
N Q
(pls)
1
2
6(5)
11
22
55
109

CONCLUSION
• IN APPLICATIONS FOR AC MOTOR CONTROL WITH BUILT IN
ENCODER, IF THE ROTATION SPEED SHOULD BE MEASURED
WITH SINGLE ALGORITHM, BETTER RESULTS ARE OBTAINED
WHEN DEDICATED QUADRATURE ENCODER IS NOT USED.
• THIS IS VALID FOR SYSTEMS WITH RELATIVLY HIGH
OPERATING FREQUENCY

PROBLEMS RELATED TO OPTOCOUPLERS
VCC_5V
from DSC
R1 U1
10k
1 2 A4N27
1 2
470
0
R2
to
IRMAX16UP60

VARIATION OF THE RISE TIME
5.4V
4.8V
4.2V
3.6V
3.0V
2.4V
1.8V
1.2V
0.6V
0.0V
-0.6V
V(n002)
V(n004)
-1.2V
20µs 40µs 60µs 80µs 100µs 120µs 140µs