2CONTENTS Introduction to hysteresis motor Constructional features Theory of hysteresis motorTorque-speed characteristicsOther features of hysteresis motorApplicationsModeling of hysteresis motorSummaryReferences
3HYSTERESIS MOTOR Synchronous motor with uniform air gap and without dc excitation.Starts by virtue of hysteresis &eddy currents induced in the rotorby action of rotating mmf of thestator windingOperates at synchronous speed.May operate from 1ø or 3ø supplyUtilizes the phenomenon ofhysteresis to produce mechanicaltorque
4CONSTRUCTIONAL FEATURES 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 operationRotor 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.
5THEORY OF HYSTERESIS MOTOR 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.
6Contd…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 bype=kef22B2 where f2 is frequency of eddy currentsAlso pe=kes2f12B2 where s is slip and f1 is stator frequencyHence torque is given by Te=pe/swsThe hysteresis loss is given byph=khf2 B1.6Also ph=khsf1 B1.6Hence torque is given by Th=ph/sws
7TORQUE-SPEED CHARACTERISTICS OF HYSTERESIS MOTOR 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.
8ADDITIONAL FEATURES OF HYSTERESIS MOTOR 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 waveThe 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.
9APPLICATIONS OF HYSTERESIS MOTOR 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 etcThe most common application is for electric clocks and other timing devicesHysteresis motors are used for rotating gyroscope rotors in inertial navigation and control systems
10MODELING OF THE HYSTERESIS MOTOR 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
12ASSUMPTIONS IN THE MODELING 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.
13The voltage and flux linkage equations are The electromagnetic torque is given byTe=(3/2)*(P/2)*(λdsiqs-λqsids)
14SUMMARYThe 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.
15REFERENCES 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 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  Ashfaq Husain “Electric Machines” 2003 Dhanpat Rai & Co. (Pvt) Ltd, pp  Sheila C Haran “Synchronous Induction and Special Machines” 2001 Scitech Publications(India) Ltd, pp  Rex Miller and Mark Richard Miller “Electric Motors” 2004 Wiley dreamtech India Pvt. Ltd, pp
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