Transcript ANALYSIS & MODELING OF HYSTERESIS MOTORS

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Introduction to hysteresis motor
Constructional features
Theory of hysteresis motor
Torque-speed characteristics
Other features of hysteresis motor
Applications
Modeling of hysteresis motor
Summary
References
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Synchronous motor with uniform
air gap and without dc excitation.
• Starts by virtue of hysteresis &
eddy currents induced in the rotor
by action of rotating mmf of the
stator winding
• Operates at synchronous speed.
• May operate from 1ø or 3ø supply
• Utilizes the phenomenon of
hysteresis to produce mechanical
torque
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The cylindrical stator structure is identical to that of
conventional induction or synchronous motors and is fitted
with a three-phase or a single-phase winding, with an auxiliary
winding and series capacitor for single-phase operation
Rotor of a hysteresis motor is a smooth solid cylinder of hard
steel(that has high hysteresis loss) and does not carry any
winding.
It is made of special magnetic material such as magnetically
hard cobalt or chrome steel having very large hysteresis loop.
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•The axis SS' of the stator m.m.f. wave revolves at
synchronous speed, because of hysteresis the
magnetization of the rotor lags behind the inducing
m.m.f. wave.
•The axis RR' of the rotor flux wave lags behind the
axis of the stator m.m.f. wave by the hysteresis lag
angle "α".
•If the rotor is stationary, starting torque is produced
proportional to the product of the fundamental
components of the stator m.m.f. and rotor flux and the
sine of the torque angle " α ".
•While the rotor is accelerating, the lag angle " α "
remains constant if the flux is constant, since the
angle " α " depends merely on the hysteresis loop of
the rotor and is independent of the rate at which the
loop is traversed.
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Stator magnetic field produces eddy currents in the rotor. They
produce their own magnetic field. Thus, there is an additional
torque on the rotor due to these eddy currents.
The eddy current loss is given by
pe=kef22B2 where f2 is frequency of eddy currents
Also pe=kes2f12B2 where s is slip and f1 is stator frequency
Hence torque is given by Te=pe/sws
The hysteresis loss is given by
ph=khf2 B1.6
Also ph=khsf1 B1.6
Hence torque is given by Th=ph/sws
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The motor develops constant torque right
up to synchronous speed.
Hysteresis motors can synchronize any
load they can accelerate, regardless of the
inertia.
After reaching synchronism the motors
continue to run at synchronous speed and
adjust their torque angle to develop
torques required by the loads.
Deviations from the ideal speed torque
curves.
*Curve A-when starting torque is
not required
*Curve B-when a high starting
torque is required.
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It has the ability to pull into synchronization any load that is
within its capacity to start and accelerate.
This motor is made in very small sizes only. Hysteresis motors
are limited to small size by the difficulty of controlling rotor
losses caused by imperfections in the stator mmf wave
The outstanding special feature of a hysteresis motor is the
production of nearly constant, ripple-free torque during
starting.
With provisions for pole changing in the stator, the motor is
multispeed.
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It has a very low noise level compared to single-phase
induction motor because it operates at one
speed(synchronous)and its rotor is smooth. With a permanent
capacitor stator, hysteresis motor is the smoothest running,
quietest single phase motor and is preferred for quality sound
reproduction equipments like record players, tape recorders etc
The most common application is for electric clocks and other
timing devices
Hysteresis motors are used for rotating gyroscope rotors in
inertial navigation and control systems
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Hystersis motor basically has the same model as that
of PM synchronous motor except that the mode of the
rotor is replaced by a nonlinear model of the
hysteresis material
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The magnetic flux is radial in the air gap and tangential in the
hysteresis rotor material.
The stator self and mutual inductances are almost independent
of the rotor position.
The rotor hysteresis ring is made of cobalt-steel material (as in
permanent magnet machines) which has a reasonable electrical
resistivity.
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The voltage and flux linkage equations are
The electromagnetic torque is given by
Te=(3/2)*(P/2)*(λdsiqs-λqsids)
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The basic idea about hysteresis motor has been dealt-its
constructional features, operation and its applications also.
A circuit model of the hysteresis motor was shown and the
modeling of the motor was done.
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[1] Omer M. Awed Badeeb “Investigation of the dynamic
performance of hysteresis motors using matlab/simulink” .
Journal of Electrical Engineering, vol. 56, NO. 3-4, 2005, pp
106–109
[2]H.R.Sourosh,A.R.Rahmati,H.Moghbelli,A.Vahedi,A.Halvaei
Niasar “Study on the hunting in high speed hysteresis motors
due to the rotor hysteresis material”. IEEE Transactions 2009,
pp 677-681
[3] Ashfaq Husain “Electric Machines” 2003 Dhanpat Rai & Co.
(Pvt) Ltd, pp 9.3-9.5
[4] Sheila C Haran “Synchronous Induction and Special
Machines” 2001 Scitech Publications(India) Ltd, pp 5.20-5.21
[5] Rex Miller and Mark Richard Miller “Electric Motors” 2004
Wiley dreamtech India Pvt. Ltd, pp 307-310
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