Purdue University Graduate School
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Airgap-less Electric Motor

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posted on 2021-08-06, 13:31 authored by Maryam AlibeikMaryam Alibeik
This dissertation focuses mainly on the airgap-less electric machine. An extensive literature review has been presented along with a systematic study that included analytical modeling, simulation with both steady-state and trasient analysis, prototype building, and experimental validation. In this type of device, the rotor is allowed to touch the stator at a contact point, which maximizes the internal flux and therefore the electromagnetic torque. A higher torque density motor is proposed in this dissertation due to a reduced reluctance caused by zero airgap situation. A comparison with other high torque density electric ma-chines demonstrates the advantages of the proposed machine. Switched reluctance motor for hybrid vehicle, integrated magnetic gear, induction machines, are some examples of the machines with lower torque density than the airgap-less electric machine. This machine will maximize the generated torque allowing these type of machines to be competitive in applications where hydraulic motors are prevalent, i.e., low-speed and high-torque requirements. Hydraulic motor systems face two major problems with their braking system and with low efficiency due to a large number of energy conversion stages (i.e., motor-pump, hydraulic connections and the hydraulic motor itself). The proposed electric motor, unlike hydraulic motors, converts electrical energy directly to mechanical energy with no extra braking system necessary and with higher efficiency. The evolution of the airgap-less electric machine from three poles to 9 bi-poles is discussed in this dissertation. The modeling of this machine with a minimum number of poles is discussed before a generalization is presented. The simulation and analysis of the airgap-less electric motor has been done using Euler integration method as well as Runge Kutta 4th order integration method due to its higher precision. A proof-of-concept electric machine with nine magnetic bipoles is built to validate the theoretical assumptions.


Degree Type

  • Doctor of Philosophy


  • Electrical and Computer Engineering

Campus location

  • Indianapolis

Advisor/Supervisor/Committee Chair

Euzeli dos Santos

Additional Committee Member 2

Brian King

Additional Committee Member 3

Lingxi Li

Additional Committee Member 4

Steven Rovnyak