Post on 11-Apr-2015
Hysteresis MotorHysteresis Motor
ConstructionConstruction
Continuously revolving magnetic field is requiredContinuously revolving magnetic field is required
StatorStator Split phase hysteresis motorSplit phase hysteresis motor Shaded pole hysteresis motorShaded pole hysteresis motor
RotorRotor No windingNo winding Smooth cylinder of hard magnetic materials with very Smooth cylinder of hard magnetic materials with very
large hysteresis loop (chrome ,cobalt steel)large hysteresis loop (chrome ,cobalt steel)
--high resistivity to reduce eddy current losshigh resistivity to reduce eddy current loss
Construction..Construction..
OperationOperation
B lags inducing magnetizing force H.B lags inducing magnetizing force H.δδ – hysteresis angle – hysteresis angle
Depends on the nature of material and hysteresis loop Depends on the nature of material and hysteresis loop - not on rotor - not on rotor
speedspeed constant from standstill to Ns.constant from standstill to Ns.
Th Th αα stator mmf * rotor mmf * sin stator mmf * rotor mmf * sin δδ
Rotor to accelerate Th>TRotor to accelerate Th>TLL
At Slip s,At Slip s, Ph = sPhPh = sPh00 ;Ph=Hyst. loss;Ph=Hyst. loss
Th= (Ph/s)*(1/Th= (Ph/s)*(1/ωωss) =Ph) =Ph00/ / ωωss
Th- independent of slip and speedTh- independent of slip and speed
AdvantagesAdvantages
Constant torqueConstant torque it can synchronize any load inertia coupled to
its shaft which it can accelerate
Smooth rotorSmooth rotor quite operationquite operation No magnetic and mechanical vibrationNo magnetic and mechanical vibration
LimitationsLimitations
the output is about one-quarter that of an induction motor of the same dimension
Low EfficiencyLow Efficiency
Low Power factorLow Power factor
low torque and available in very small low torque and available in very small sizes sizes
ApplicationsApplications
Constant speed applications Constant speed applications Electric clock (gear train used)Electric clock (gear train used)
Air conditionerAir conditioner
Sound recording and sound producing Sound recording and sound producing instrumentsinstruments Tape recordersTape recorders Record playersRecord players