Non-Synchronous Operation of a Hysteresis Machine

  • Suresh C. Bhargava

Student thesis: Doctoral ThesisDoctor of Philosophy


A detailed study is made of the field distribution
in a hysteresis machine, having a mechanically rotated magnetic
field, for non-synchronous speeds. A qualitative theory of
operation is developed and the Poynting vector concept of nett
power flow used to predict the torque-excitation characteristic.

Constructional details of the experimental machine are
given and the tests performed for the measurement of torque and
magnetic flux density are described. A comprehensive
interpretation of the magnetic flux density waveforms is given,
with special regard to those obtained in the non-magnetic
regions. To demonstrate the significance of the low relative
permeability of the rotor active material alone, experiments
with a non-metallic, non-magnetic rotor and on analogue models
are conducted, and verified analytically. In the light of
these results, the spatial hysteresis effect of the rotor on the
field distribution is discussed.

The qualitative theory brings out clearly the physical
operation of the machine. It establishes a new concept of
‘independent' rotor magnetisation, derived from the permanent
magnet properties of the rotor, as the connecting link between
the rotating magnetic field and the production of torque.
The spatial hysteresis effect on the airgap magnetic field is
explained by reference to this rotor magnetisation.

Poynting's theorem is applied to calculate the power
flow in the machine. The developed torque is obtained as the
difference between the nett power flow in the airgap and arbor
regions of the rotor. This eliminates the necessity of.
measuring the magnetic field components within the rotor
magnetic material. The calculated torque—excitation curve
shows satisfactory correlation with the measured characteristic.
Date of Award1972
Original languageEnglish


  • non-synchronous operation
  • hysteresis machine

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