Mohammad T. N. Mohammad

The University of Sheffield, Sheffield, England, United Kingdom

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Publications (2)2.33 Total impact

  • Source
    M.T.N. Mohammad · C.N. Booth · P. Hodgson · L. Howlett · P.J. Smith · S.M. Sharkh
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    ABSTRACT: This paper discusses design considerations for a water cooled high acceleration 3-phase air-cored brushless DC PM linear actuator used in a vacuum radiation environment. Radiation can cause damage to magnets, and the requirement for a vacuum chamber around the moving parts imposes additional constraints that further complicate the electromagnetic and mechanical design of the actuator. This paper discusses the selection of suitable materials and bearings that are compatible with operation in vacuum and can cope with the required millions of actuation cycles. The selection of suitable bearings with low friction and wear is discussed and the design of a low inertia shaft is described. The factors that have an influence on the susceptibility of the magnets to radiation damage are discussed. These factors include magnet dimensions, magnet material, external magnetic field, temperature and the directions of both the magnetic flux and radiation. FLUKA simulations are presented showing the fluences of protons, neutrons, electrons and gamma radiation to which the magnets are exposed. Based on these simulations, loss of magnetisation for different magnet materials can be predicted, and used to estimate the effect of magnet radiation ageing on actuator current, and increased temperature rise. The paper also presents transient electromagnet FEA computation of the force produced by the actuator when magnets are housed in a stainless steel vacuum chamber.
    Preview · Conference Paper · May 2008
  • Source
    Suleiman M. Abu Sharkh · Mohammad T. N. Mohammad
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    ABSTRACT: The paper describes a double-gap axial field permanent magnet (PM) dc motor whose double-layer armature wave winding is constructed of copper strips. It investigates the performance of two machines using powder iron and lamination steel materials as armature teeth. Tests are conducted to evaluate the motor torque and speed curves as well as their efficiency under different loads. Finite element analysis (FEA) and equivalent circuit models are used to determine the levels of the magnetic saturation in the motors; calculate torque, inductance, and electromotive force (EMF); and determine the distribution of losses in the machine. The results show that the powder iron armature machine has lower back EMF and torque constants, and is less efficient than the steel laminations machine, which is due to the lower permeability and saturation flux density of the powder iron material.
    Preview · Article · Oct 2007 · IEEE Transactions on Energy Conversion