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Guided by Submitted by
Prof. Vijayakumari C K Anoop S
S7 EEE
Roll no: 10
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CONTENTS
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 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.
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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
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EXCITATION
MODE
GENERATION
MODE
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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
toerqffuiceiency of braking
operation
copper loss
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 The average torque of an SRM is computed as
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 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
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 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.
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EFFECTS OF TURN-OFF
ANGLE
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 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.
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 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.
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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.
torque per average excitation power.
torque per phase rms current.
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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.
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REFERENCES
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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.

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Braking Operation of SRM Drives

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