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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GENERATION

MODE

EXCITATION

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

torqueefficiency of braking

operation

copper loss

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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

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EFFECTS OF CURRENT

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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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EFFECTS OF TURN-ON ANGLE

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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.

the maximum average braking

torque per average excitation power.

the maximum average braking

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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THANK

YOU