SRM Class Notes (2)

7/29/2019 SRM Class Notes (2)

1/40

Unit III

SRM


2/40

2

Introduction of SRM :

The reluctance motor is an electric motor in whichtorque is produced by the tendency of its moveable part to

move to a position where the inductance of the excited

winding is maximized.

Principle of SRM

SRM develops torque through an interact ion between

the electrom agnet exci tat ion from the stator poles and

the rotor teeth, once a particu lar combinat ion o f phasecomment is establ ished and maintained in the stator,

the rotor pole wi l l be alignm ent wi th the stator po le in

that part icu lar po si t ion.


3/40

Basic structure of SRM

3

Stator pole

Rotor

pole


4/40

4

When one stator phase is energized, its stator

pole pair attracts the closest rotor pole pairinto alignment producing torque.

By the consecutive energization of successivephases, continuous rotation in either directionis possible.


5/40

5

The direction of rotation of motor depends

upon the sequence of switching the stator

windings.


6/40


7/40

Construction of SRM

7


8/40

BLOCK DIAGRAM OF SRM


9/40


10/4010

OPERATION PRINCIPLE

OPERATION PRINCIPLE


11/40

OPERATION PRINCIPLE

cont..

11

OPERATION PRINCIPLE


12/40

OPERATION PRINCIPLE

cont..

12


13/40


14/40

TorqueandInductanceplot


15/40

Aligned position

Unaligned Position

15


16/4016

When one stator phase is energized, the statorpole pair attracts the closest rotor pole pairinto the field.

Torque produced on the basis of varyingreluctance along the magnetic circuit.


17/4017

When one stator phase is energized, the statorpole pair attracts the closest rotor pole pairinto the field.

Torque produced on the basis of varyingreluctance along the magnetic circuit.


18/4018

T=1/2 { i2(dL/d)}

L- inductance

-rotor angular position

i- current

T- torque


19/40

19

Torque ripple pulsations are most significantat the commutation instants when torque

production mechanism is being transferred

from one active phase to another.

%Ripple factor = Tmax-Tmin* 100

Tavg


20/40

20

Geometry

Switching devices in the input side


21/40

21


22/40

Conventional type24/18-pole

BS=6.9,br=7.4


23/40

24/18 POLE ANIMATED SRM

BS=6.9,br=7.4


24/40

24

ADVANTAGES

The rotor does not have any windings.

Its strong and rugged constructionIt provides high reliability, wide-speed range

at constant power.

DISADVANTAGESDoubly-salient structure causes vibration

and acoustic noise.

High torque-ripple


25/40

25

Possible Research Potential in SRM

1. Reducing vibration and noise.

2. Diminishing the torque ripples and

Improvising the torque output.

3. Geometrical variations to reduce

weight.

4. DSP based power converter for SRM -reducing torque r ipples .


26/40

POWER CONVERTER

CIRCUIT

Application

Converter design

Cost of drive

Basic requirement

Freewheel chopping period

Demagnetizing energy back to supply


27/40

TYPE OF CONVERTERS

Classic converter.

n+1 power converter.

Phase winding converter.

Spilit power converter.

Dump c Converter.


28/40

Classic converter.


29/40

Performance of CC

ADVANDAGE :

1. Control of each phase is completely

independent of the other source

2. Switching losses less

3. The energy from the off going phase is

feed back to the source, which result in

useful utilization of the energy .


30/40

Performance of CC

Disadvantage:

Higher no of switches required in each

phase which makes the converter

expensive and used for low voltage

regulation .


31/40

n+1 POWER CONVERTER.


32/40

Performance of CC

Advantage :

1. The converter used lower number of

switching devices, so less cost2. the converter is able to free wheel during

the chopping ,thus reducing the switchingfrequency and losses .

3. Voltage rating of all switching devices andthe diode are low .

High torque ripple during de.. And mag.


33/40

Split power converter.


34/40

Performance of SPLIT C

Lower no switching devices

Fast demagnetizing of phase during

commutation

It is not feasible for low voltage

application


35/40

DUMP C CONVERTER.


36/40

Current Control Schemes

Based on current control

1. Hysteresis type current regulator

2. PWM type current regulator


37/40

HYSTERESIS TYPE CURRENT

REGULATOR


38/40

PWM type current regulator


39/40

Computer Based Control Of

SRM


40/40

40

ADVANTAGES

The rotor does not have any windings.

Its strong and rugged constructionIt provides high reliability, wide-speed range

at constant power.

DISADVANTAGESDoubly-salient structure causes vibration

and acoustic noise.

High torque-ripple

SRM Class Notes (2)

Documents

Transcript of SRM Class Notes (2)