Prepared by: Luis Fernando Montoya Chun-Ju Huang Ashish K. Solanki Speed control of squirrel cage...
-
Upload
mitchell-carter -
Category
Documents
-
view
213 -
download
0
Transcript of Prepared by: Luis Fernando Montoya Chun-Ju Huang Ashish K. Solanki Speed control of squirrel cage...
Introduction Applications of AC drives Types of Methods to control the speed of Induction machine V/F controlPower ConvertersSimulation ModelSimulation Results Conclusion Reference
2
An electric drive system consisting of electric motor, its power controller and energy transmitting shaft consisting of load
Types of Drive system (1)DC Drive(2)AC Drive AC Drives are mostly used in Industry.
Introduction
3
Advantages and disadvantages of AC Drives compare to DC Drives
Advantages of ac drives 1. For the same rating, ac motors are lighter in weight as compared
to dc motors.2. AC motors require low maintenance.3. AC motors are less expensive.4. AC motors can work in dangerous areas like chemical,
petrochemical etc. Disadvantage of ac drives1.Power converters for the control of ac motors are more complex.2.Power converter for ac drives are more expensive.3.Power converters for ac drives generate harmonics in the supply
system and load circuit. 4
Industrial applicationsInduction motors with squirrel cage rotors are the workhorse of
industry because of their low cost and rugged construction.When Squirrel cage induction machine is operated directly from
the line voltages(60 Hz/50 Hz essentially constant voltage) an Induction motor is operated at constant speed. However in the industry we required to vary the speed of an Induction motor. This can be done by Induction motor drives.
Main application of Induction Motor drives: Fans, Compressor, Pumps, blowers, machine tools like lathe,
drilling machine, lifts, conveyer belts etc.
5
Methods of Speed Control of Induction motors
(1) Stator voltage Control (2) Stator Frequency Control (3) Stator Current Control(4) V/F Control (5) Slip power recovery Control ( Wound Rotor Induction
Machine)
6
Curve of the behavior of the Induction Machine
7
• During start up. Normally draws up to seven times the rated current.
• Normally delivers approximately 1.5 the rated torque, when starting
• When operating at base speed if the load is increased, the motor will start slowing down and the slip will increase.
•But if the load is increased beyond the Break down torque, the machine wont be able to recover.
V/Hz Theory BackgroundThe induction motor
draws the rated current and delivers the rated torque at the base speed.
As mentioned before the motor can take up to 2.5 load increase, with 20% drop in the speed.
8
Description of the principle
Assume the voltage applied to the Motor is AC, and the voltage drop across the Armature resistance very small. Then at the steady state we get:
(Voltage applied at the stator, and Flux)
Since the V/f relation keeps constant, then the flux remains constant and the torque is independent of the supplied frequency.
9
Description of the PrincipleSince the flux is maintained
constant, the toque developed depends only on the slip speed.
Huge starting torque can be obtained without heating-up the machine
10
Simulation ResultsInput Voltage for 3 phase uncontrolled Rectifier
4.14 4.145 4.15 4.155 4.16 4.165 4.17 4.175
-400
-300
-200
-100
0
100
200
300
Time(s)
Inpu
t V
olta
ge t
o re
ctifi
er(V
)
Voltage input to rectifier
Vin A
Vin BVin C
21
Simulation ResultsOutput Voltage of three phase uncontrolled rectifier
0.08 0.1 0.12 0.14 0.16 0.18 0.2 0.22 0.24
-300
-200
-100
0
100
200
300
Time(s)
Out
put
Voltage o
f R
ectif
ier(
V)
Vin A
Vin B
Vin C
Rectified Output voltage
22
Simulation ResultsOutput Voltage of DC/DC Boost converter
0 2 4 6 8 10 12 14 16 18 200
50
100
150
200
250
300
350
400
Time(s)
Out
put V
olta
ge o
f DC
DC C
onve
rter(V
)
Output Voltage of DC DC Converter
Vdc out
23
Simulation ResultsOutput Voltage of 3 Phase PWM inverter before filter
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5-500
0
500
Time(s)Voltag
e Outp
ut inv
erter(
V))
Output Voltage of Inverter before filter
Vout inv A
Vout inv BVout inv C
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5-500
0
500
Time(s)
Voltag
e Outp
ut inv
erter
phase
A(V))
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5-500
0
500
Time(s)
Voltag
e Outp
ut inv
erter
phase
B(V))
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5-500
0
500
Time(s)
Voltag
e Outp
ut inv
erter
phase
C(V))
24
Simulation ResultsOutput Voltage of Inverter after filter
( Controlled Input voltage given to Induction motor)
0 2 4 6 8 10 12 14 16 18 20-250
-200
-150
-100
-50
0
50
100
150
200
250
Time(s)
Vol
tage
Inpu
t to
Mac
hine
(V)
Output Voltage of Inverter after filter(input Voltage to Machine)
Vin m A
Vin m BVin m C
3.68 3.7 3.72 3.74 3.76 3.78 3.8 3.82 3.84 3.86 3.88
-200
-150
-100
-50
0
50
100
150
200
Time(s)
Voltage I
nput
to M
achin
e(V
)
Output Voltage of Inverter after filter(input Voltage to Machine)
Vin m A
Vin m B
Vin m C
25
Simulation ResultsStator Current
3.55 3.6 3.65 3.7 3.75 3.8 3.85 3.9
-10
-8
-6
-4
-2
0
2
4
6
8
10
Time(s)
Sta
tor
Curr
ent(
A)
Stator Current
Istator A
Istator BIstator C
26
Simulation ResultsRotor Reference speed and Actual Speed
Here the reference speed is 1000 rpm= 104.72 rad/sec
0 2 4 6 8 10 12 14 16 18 20-20
0
20
40
60
80
100
120
Time(s)
Roto
r S
peed (
rad/s
ec)
Rotor Speed
Reference Speed
Actual Speed
27
Simulation ResultsRotor Reference speed and Actual Speed
0 2 4 6 8 10 12 14-10
0
10
20
30
40
50
60
70
80
90
100
Time(s)
Roto
r S
peed (
rad/s
ec)
Rotor Speed
Reference Speed
Actual Speed
0 2 4 6 8 10 12 14 16 18 20-20
0
20
40
60
80
100
120
140
Time(s)
Roto
r S
peed (
rad/s
ec)
Rotor Speed
Reference Speed
Actual Speed
0 2 4 6 8 10 12 14 16 18 20-20
0
20
40
60
80
100
120
140
160
180
Time(s)
Roto
r S
peed (
rad/s
ec)
Rotor Speed
Reference Speed
Actual Speed
Reference speed is 1300 rpm=136.14 rad/sec
Reference speed is 600rpm= 62.83 rad/sec
Reference speed is 1500rpm= 157.08 rad/sec
29
Rotor Reference speed and Actual Speed
Reference Speed is changed from 104.71 rad/sec to 92.24 rad/sec
0 2 4 6 8 10 12 14 16 18 20-20
0
20
40
60
80
100
120
Time(s)
Roto
r S
peed (
rad/s
ec)
Rotor Speed
Reference Speed
Actual Speed
30
ConclusionIn Case of Squirrel cage induction motor the slip
cannot be increase above certain limit, the operating speed range is very less. By applying the V/F control we can get the large operating range by keeping V/F ratio constant.
31
Reference[1] Modern Power Electronics and AC drives by Bose, Bimal K. [2] POWER ELECTRONICS Converters, Applications and Design
by Ned Mohan[3] Power electronics Lecture Notes by Prof. Nasiri[4] Lecture Notes by Dr. Omar[5] AC Induction Motor Control using Constant V/Hz Principe
and Space Vector PWM Technique with TMS320 C240[6] Speed Control of 3-Phase Induction Motor Using PIC18
Microcontrollers
33