Date post: | 15-Jul-2015 |
Category: |
Engineering |
Upload: | anoop-s |
View: | 108 times |
Download: | 2 times |
Guided by Submitted by
Prof. Vijayakumari C K Anoop S
S7 EEE
Roll no: 10
1
CONTENTS
2
INTRODUCTION
MECHANISM OF BRAKING
CONTROL SCHEMATIC
CRITERIA
EFFECT OF
• CURRENT
• TURN OFF ANGLE
• TURN ON ANGLE
CONCLUSION
INTRODUCTION
Electric vehicles - environment friendly, cost
effective.
Motors used – DC motor, BLDC motor, AC
induction motor, SRM motor.
SRM - simple motor construction, low weight,
high torque density, direct-drive and simple
drivetrain system.
Main advantage of EV’s is electro braking.
Effective braking operation of SRMs is important
for EVs with better performances.
3
MECHANISM OF BRAKING
OPERATION OF SRM DRIVES
Braking operation is just the generating operation
and it lasts by a short time in EVs.
Braking operation of SRMs includes two modes
Excitation mode
Generation mode
4
GENERATION
MODE
EXCITATION
MODE
5
CONTROL SCHEMATIC OF
BRAKING OPERATION IN SRM
DRIVES
The turn-on and the turn-off angles are defined to
control the braking torque.
The current reference with the hysteresis current
controller is used to adjust the average value of
braking torque.6
CRITERIA OF BRAKING
OPERATION
Average torque
Average braking torque per
average excitation power
Average braking torque per
rms current
magnitude of braking
torqueefficiency of braking
operation
copper loss
7
8
The average torque of an SRM is computed as
Tp - time value of an electrical period
Nph – number of phases
Tphk – instantaneous torque produced by a
phase
The average excitation power under braking
operation is
The positive power indicates that the SRM takes
in electric power from the DC link.
The negative power indicates that the SRM
output electric power to DC link.
The rms value of phase current is
The average braking torque per average
excitation power is expressed as
The average braking torque per rms current is
9
EFFECTS OF CURRENT
10
11
12
Large current reference results in large average
braking torque
The average braking torque per average
excitation power changes with the current
reference and
The average braking torque per phase rms
current goes up with increase in the current
reference.
13
EFFECTS OF TURN-OFF
ANGLE
14
15
16
There are optimal turn-off angles to have the maximum average braking torque
The maximum average braking torque per average excitation power can be obtained when the turn-off angles are equal to the optimal values, and
There are always the optimal turn-off angle such that the average braking torque per rms current value reaches to the maximum value.
17
EFFECTS OF TURN-ON ANGLE
18
19
20
The average braking torque becomes small if the turn-on angle increases
Variation in the turn-on angle result in little effect on the average braking torque per average excitation power and
The average braking torque per phase rms current decreases with increase in the turn-on angle.
The small turn-on angle is advantageous for braking operation of SRM drives.
21
CONCLUSIONS:
The large current reference is beneficial to the
desired braking operation of SRM drives in EVs.
The turn-off angle can be optimized to obtain:
the maximum average braking
torque.
the maximum average braking
torque per average excitation power.
the maximum average braking
torque per phase rms current.
22
CONCLUSIONS…….
the turn-on angle has considerable effects on
braking operation of SRM drives.
the small turn-on angle is advantageous for
braking operation of SRM drives.
23
REFERENCES
24
1) Omekanda, A.M.; Gopalakrishnan, S.; Klode, H.;
“Acoustic Noise ofSwitched Reluctance and
Permanent Magnet Motors: A Comparison in the
Context of Electric Brakes”, 42nd IAS Annual
Meeting, 2007, pp.2147 – 2153.
2) X. D. Xue, K. W. E. Cheng, and N. Cheung,
“Selection of Electric Motor Drives for Electric
Vehicles”, presented at AUPEC 2008,
Sydney,Australia.
3) X. D. Xue, K. W. E. Cheng, and S. L. Ho, “A
Position Stepping Method for Predicting
Performances of Switched Reluctance Motor
Drive”,IEEE Transactions on Energy Conversion,
vol. 22, no. 4, Dec 2007, pp.839-847.
25
THANK
YOU