The presentation contains the details about construction and working of Rotary and linear switched reluctance motors

1. ROTARY AND LINEAR SWITCHED
RELUCTANCE MOTORS
CONTENTS
INTRODUCTION
ROTARY SRM
CONSTRUCTION
DIAGRAM
OPERATING PRINCIPLE
LINEAR SRM
CONSTRUCTION
DIAGRAM
OPERATING PRINCIPLE
APPLICATIONS OF SRM
Kongunadu College of Engineering & Technology Switched Reluctance Motor

2. INTRODUCTION
 The switched reluctance motor (SRM) is a type of
stepper motor, an electric motor that runs by
reluctance torque.
 This greatly simplifies mechanical design as power
does not have to be delivered to a moving part, but it
complicates the electrical design as some sort of
switching system needs to be used to deliver power
to the different windings.
 Electronic devices can precisely time switching,
facilitating SRM configurations.
Kongunadu College of Engineering & Technology Switched Reluctance Motor

3. ROTARY SRM
CONSTRUCTION - STATOR
 The stator is made up of silicon steel stampings with
inward projected poles.
 The number of poles. The number of poles of the stator
can be either an even number or an odd number.
 Most of the motors available have even number of stator
poles (6 or 8). All these poles carry field coils.
 The field coils of opposite poles are connected in series
such that their mmf‘s are additive and they are called
phase windings.
 Individual coil or a group of coils constitute phase
windings. Each of the phase windings are connected to
the terminal of the motor.
 These terminals are suitably connected to the output
terminals of a power semiconductor switching circuitry,
whose input is a d.c. supply.
Kongunadu College of Engineering & Technology Switched Reluctance Motor

4. CONSTRUCTION - ROTOR
 The rotor is also made up of silicon steel stampings with
outward projected poles.
 Number of poles of rotor is different from the number of
poles of the stator.
 In most of the available motors the number of poles of
the rotor is 4 or 6 depending upon the number of stator
poles 6 or 8.
 The rotor shaft carries a position sensor. The turning ON
and turning OFF operation of the various devices of the
power semiconductor circuitry are influenced by the
signals obtained from the rotor position sensor.
Kongunadu College of Engineering & Technology Switched Reluctance Motor

5. DIAGRAM
Kongunadu College of Engineering & Technology Switched Reluctance Motor

6. PRINCIPLE OF OPERATION
 To start with stator pole axis AA‘ and rotor pole axis aa‘
are in alignment as shown in diagram
 They are in the minimum reluctance position so far as
phase windings is concerned.
 Then dLa/dθ=0. At this position inductance of B windings
is neither maximum nor minimum. There exists dLb/dθ
and dLc/dθ.
 Now if B phase is energized then the rotor develops a
torque because of variable reluctance and existences of
variation in inductance.
Kongunadu College of Engineering & Technology Switched Reluctance Motor

7.  The torque developed is equal to (1/2)iB2(dLB/dθ). This
direction is such that BB‘ and bb‘ try to get aligned.
 If this torque is more than the opposing load torque and
frictional torque the rotor starts rotating.
 When the shaft occupies the position such that BB‘ and
bb‘ are in alignment (i.e.,) θ=30°, no torque is
developed as in this position dLB/dθ=0.
 Thus electrical to mechanical power conversion takes
place.
Kongunadu College of Engineering & Technology Switched Reluctance Motor

8. LINEAR SWITCHED RELUCTANCE MOTOR
CONSTRUCTION
 The stator construction of linear SRM can be
classified into two types.
 Active stator. ( With windings)
 Passive stator. ( Without windings)
 Active stator has windings and alternate poles .the
windings are evenly distributed. There are group of
coils are present in the stator slots. Passive stator
has no windings and only has poles and iron core
laminations.
 Translator has no windings and only has poles and
iron core laminations. Which has alternate poles.
Kongunadu College of Engineering & Technology Switched Reluctance Motor

9. DIAGRAM
Kongunadu College of Engineering & Technology Switched Reluctance Motor

10. PRINCIPLE OF OPERATION
 When the applying the supply to the stator, the coils
are energized and also the reluctance between
stator and rotor poles are varied.
 Due to the variation of reluctance the stator create
the linear force.
 Thus the translator moved as per the energization
of stator coils.
Kongunadu College of Engineering & Technology Switched Reluctance Motor

11. APPLICATIONS OF SRM
 Washing machines
 Vacuum cleaner
 Automobile applications
 Robotics control applications
Kongunadu College of Engineering & Technology Switched Reluctance Motor

12. REFERENCES
S.No Books / Web Sources
1. K.Venkataratnam, ‘Special Electrical Machines’, Universities Press (India) Private Limited, 2008
2. T.J.E. Miller, ‘Brushless Permanent Magnet and Reluctance Motor Drives’, Clarendon Press,Oxford, 1989.
3. T. Kenjo, ‘Stepping Motors and Their Microprocessor Controls’, Clarendon Press London, 1984.
4.
R.Krishnan, ‘Switched Reluctance Motor Drives – Modeling, Simulation, Analysis, Design andApplication’, CRC
Press, New York, 2001.
5. P.P. Aearnley, ‘Stepping Motors – A Guide to Motor Theory and Practice’, Peter Perengrinus ,London, 1982.
6. T. Kenjo and S. Nagamori, ‘Permanent Magnet and Brushless DC Motors’, Clarendon Press, London, 1988.
7. K.Dhayalini, “Special Electrical Machines,” Anuradha Publications, 2017.
8. Google and Wikipedia
Kongunadu College of Engineering & Technology Switched Reluctance Motor