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Robot and Servo Drive Lab.
Design of a Synchronous Reluctance Motor Drive
T. J. E. Miller, Senior Member, ZEEE, Alan Hutton, Calum Cossar, and David A. Staton
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 21, NO. 4, JULYIAUGUST 1991
學生: Guan Ting Lin
指導老師: Ming Shyan Wang
Department of Electrical Engineering
Southern Taiwan University
2016/7/13
Outline
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Abstract
Introduction
Basic theory
Evolution of the design
Electronic control
Conclusion
References
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Department of Electrical Engineering
Southern Taiwan University
Robot and Servo Drive Lab.
Abstract
segmental-rotor synchronous reluctance motor is used in a variable-speed drive
with current-regulated PWM control.
The low-speed torque capability is compared with those of an induction motor, a
switched reluctance motor, and a brushless dc PM motor of identical size and
copper weight.
2016/7/13
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Department of Electrical Engineering
Southern Taiwan University
Robot and Servo Drive Lab.
Introduction
The main features of the synchronous reluctance motor are as follows:
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The rotor is potentially less expensive than the PM rotor. Because it requires no
cage winding, it is lighter and possibly cheaper than an induction-motor rotor.
The torque per ampere is independent of rotor temperature, unlike that of the
PM or induction motors.
The stator and the inverter power circuit are identical to those of the induction
motor or PM synchronous motor drives.
The control is simpler than that of the field-oriented induction motor drive,
although shaft position feedback is necessary.
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Department of Electrical Engineering
Southern Taiwan University
Robot and Servo Drive Lab.
Basic theory
The inverter-fed SYNCHREL motor is freed from the old constraints of the
line-start version as follows:
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No starting cage is necessary. The rotor can therefore be designed purely for
synchronous performance.
Electronic control makes the motor autosynchronous. Therefore, the torque angle
can be set to maximize torque per ampere at all loads and speeds without concern
for pullout.
There is no need for amortisseur currents to prevent rotor oscillations. This makes
it possible to design for the highest possible ratio of the synchronous reactances x,
and x d without concern for stability.
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Department of Electrical Engineering
Southern Taiwan University
Robot and Servo Drive Lab.
Basic theory
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Because the SYNCHREL motor is a classical synchronous machine, its
electromagnetic torque is given by (l), where Id and I, are components of
the rms phase current I resolved along the d and q axes of the phasor
diagram; they correspond to the space-vector components of stator mmf
along the d and q axes of the rotor:
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Department of Electrical Engineering
Southern Taiwan University
Robot and Servo Drive Lab.
Basic theory
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The torque per ampere is maximized if the phase current is oriented at 45°
to the q axis so that Id and I, are equal in magnitude. Since Ld < Lq, Id must
be negative, and therefore, the current leads the q axis in the phasor
diagram (Fig. 2).
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Department of Electrical Engineering
Southern Taiwan University
Robot and Servo Drive Lab.
Basic theory
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For a peak airgap flux density of 0.8 T and a saturation density of around
1.7 T, t must be limited to the order of 0.5. Now, the synchronous
reactance X, is inversely proportional to the airgap length g, the linear
magnetic theory developed it can be shown that Xd is inversely proportional
to the sum of g and the combined thickness of the flux barriers, which is
very roughly equal to tR, where R is the rotor radius. Therefore, the
saliency is given approximately by
2016/7/13
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Department of Electrical Engineering
Southern Taiwan University
Robot and Servo Drive Lab.
Evolution of the design
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Three rotors have been built,
and the cross sections of two
of these are shown in Fig. 4.
The pole pieces are held by
two thin ribs that attach to
the q axis webs in the same
way as in the interior magnet
motor described by Jahns.
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Department of Electrical Engineering
Southern Taiwan University
Robot and Servo Drive Lab.
Evolution of the design
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Fig. 6(a) and (b) show typical
d- and q-axis finite-element
flux plots. The calculation of
magnetization curves is a
straightforward exercise of
the finite-element method
o n c e th e m a g n et i z a t io n
characteristics of the core
steel are accurately known.
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Department of Electrical Engineering
Southern Taiwan University
Robot and Servo Drive Lab.
Electronic control
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The configuration of the electronic control for two-phase motor is shown in
Fig. 9. A 360-pulse magnetoresistive encoder mounted on the motor shaft
generates an indexed pulse count representing the rotor position. This count
is used to address two EPROM's: one for the d axis and one for the q axis
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Department of Electrical Engineering
Southern Taiwan University
Robot and Servo Drive Lab.
Conclusion
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These results have been achieved with a single flux-barrier design capable
of accommodating permanent magnets. The inductance ratio is much
smaller than theoretically possible in a pure SYNCHREL motor, and much
better results would be expected with an axially laminated construction or
equivalent.
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The comparison of motor types underlines the superiority of the PM
brushless dc motor in raw torque production at low speed and its ability to
tolerate a large airgap length. The comparison also highlights the weakness
of the induction motor in this small size range.
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Department of Electrical Engineering
Southern Taiwan University
Robot and Servo Drive Lab.