Transcript MODELLING AND CONTROL OF SYNCHRONOUS RELUCTANCE MOTOR

By
JAIKRISHNA . V
Edited By
Sarath S Nair
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 Introduction
 Principle of Operation
 Mathematical Model of Synchronous Reluctance Motor
 Advantages and Disadvantages
 Comparison with other motors
 Summary
 References
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 Synchronous reluctance motor is a true ac motor
 Synchronous reluctance motors were developed to
provide an efficient constant speed machine.
 There are no brushes, slip rings etc.
 Its principle is almost similar to salient pole
synchronous motor.
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 In principle, the Synchronous Reluctance Motor is similar




to the traditional salient pole synchronous motor but does
not have an excitation winding in its rotor.
The rotor is constructed with salient poles
The SynRM includes a squirrel cage on the rotor to provide
the starting torque for line-start.
The squirrel cage was also needed as a damper winding in
order to maintain synchronism under sudden load torques
When 3 phase supply is given to the stator, a rotating flux is
produced. Initially emf is induced in damper winding and
the motor starts like an induction machine. As it
approaches synchronous speed the reluctance torque takes
over and the motor locks into synchronous speed.
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1)
d-q equation of synchronous reluctance motor
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• In synchronous reluctance motor, the excitation
winding does not exist.
• The basis for the d – q equations for a synchronous
reluctance machine can be obtained from parks
equation
vd = rs ids + dλds/dt – wr λqs
vq = rs iqs + dλqs/dt + wr λds
(1)
λds = Lls ids + Lmd ids = Lds ids
λqs = Lls iqswww.technologyfuturae.com
+ Lmq iqs = Lqs iqs
(2)
Where
where Lls - stator leakage inductance
Lmd – direct axis magnetizing inductance
Lmq – quadrature axis magnetizing inductance
Te = (3/2)*(P/2)*(λds iqs - λqs ids)
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(3)
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 The variable in equation (1) will become constant in
steady state .ie., d/dt terms can be eliminated
Ids = we Lqs Vqs + rs Vds
rs² + we² Lds Lqs
(5)
Iqs = -we Lds Vds + rs Vqs
rs² + we² Lds Lqs
Neglecting stator resistance we get
Ids = Vqs
, Iqs = - Vds
(6)
we Lds
we Lqs
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Single phasor equation from a steady state version of
equation (1) can be obtained by multiplying first line
of(1) ie. vds by –j and adding to the second line ie. vqs
vqs – jvds = rs(Iqs – jIds) + we(λds + jλqs) (7)
or using (2) and (7)
vqs - jvds = rs(Iqs – jIds) + we(Lds Ids + jLqs Iqs) (8)
It can be changed to
Vqs – jVds = rs(Iqs – jIds) + jwe Lds(-jIds) + jwe Lqs Iqs
(9)
In phasor notation
(10)
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(11)
Except frequencies near zero, in all frequencies
neglecting stator resistance
(12)
Substituting Vds and Vqs obtained from
phasor diagram we get
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(13)
The torque varies as square of volt per Hertz and as the
sine of twice of the angle ∂. When the volt/Hertz is
fixed, the maximum torque is clearly reached when
∂=45˚. Therefore Maximum torque
(14)
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If λds and λqs is directly substituted into the torque
equation Te can also be written in terms of stator d-q
current as:
(15)
Substitute the value of Ids and Iqs
(16)
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Electromagnetic torque can be expressed in terms of
stator current amplitude and mmf angle ε as
(17)
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 Freedom from permanent magnets
 A wide speed range at constant power
 Synchronous operation leading to high efficiency
 Ability to maintain full torque at zero speed
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•
In small motors the torque/ampere and the torque/
volume are lower than in PM motors
•
The air gap is small when compared to induction
motors
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1.
Induction motor
 Rotor losses lower than those of the induction
machine
 High power factor and higher continous torque rating
 The full load efficiency at rated speed and the speed
range at constant power, also exceed the values
obtainable with induction motors.
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2.
Switched reluctance motors
• does not suffer from high torque ripple.
• Power density lower than Switched reluctance motor
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 Principle of operation of synchronous reluctance
motor are discussed.
 The mathematical model of Synchronous reluctance
motor was also discussed.
 Comparisons with different motors has been done
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[1] Srge Edward Lyshevski, Alexander Nazarov, Ahmed El- Antably,
Charles Yokomoto, A.S.C. Sinha, Maher Rizkalla and Mohamed
El – Sharkawy, “Design and Optimization, Steady-State and
Dynamic Analysis of Synchronous Reluctance Motors Controlled
by Voltage-Fed Converters With Nonlinear Controllers”, IEEE
Trans. Industry Applications, Sept.1999.
[2] Peyman Niazi, “Permanent Magnet Assisted Synchronous
Reluctance Motor Design And Performance Improvement”, Texas
A&M University
[3] R. E. Betz, R. Lagerquist, M. Jovanovic, T. J. E. Miller and R. H.
Middleton, “Control of synchronous reluctance machines,” IEEE
Trans. Industry Applications, vol. 29, no. 6, pp. 11 10-1 122, 1993.
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