PMSM, Permanent magnet, Cryogenic, High speed, Electric machines, Motor design


This dissertation is concerned with the design of permanent magnet synchronous motors (PMSM) to operate at super-high speed with high efficiency. The designed and fabricated PMSM was successfully tested to run upto 210,000 rpm The designed PMSM has 2000 W shaft output power at 200,000 rpm and at the cryogenic temperature of 77 K. The test results showed the motor to have an efficiency reaching above 92%. This achieved efficiency indicated a significant improvement compared to commercial motors with similar ratings. This dissertation first discusses the basic concept of electrical machines. After that, the modeling of PMSM for dynamic simulation is provided. Particular design strategies have to be adopted for super-high speed applications since motor losses assume a key role in the motor drive performance limit. The considerations of the PMSM structure for cryogenic applications are also discussed. It is shown that slotless structure with multi-strand Litz-wire is favorable for super-high speeds and cryogenic applications. The design, simulation, and test of a single-sided axial flux pancake PMSM is presented. The advantages and disadvantages of this kind of structure are discussed, and further improvements are suggested and some have been verified by experiments. The methodologies of designing super high-speed motors are provided in details. Based on these methodologies, a super high-speed radial-flux PMSM was designed and fabricated. The designed PMSM meets our expectation and the tested results agree with the design specifications. 2-D and 3-D modeling of the complicated PMSM structure for the electromagnetic numerical simulations of motor performance and parameters such as phase inductors, core losses, rotor eddy current loss, torque, and induced electromotive force (back-EMF) are also presented in detail in this dissertation. Some mechanical issues such as thermal analysis, bearing pre-load, rotor stress analysis, and rotor dynamics analysis are also discussed. Different control schemes are presented and suitable control schemes for super high- speed PMSM are also discussed in detail.


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Graduation Date





Sundaram, Kalpathy B.


Doctor of Philosophy (Ph.D.)


College of Engineering and Computer Science


Electrical and Computer Engineering

Degree Program

Electrical Engineering








Release Date

January 2008

Length of Campus-only Access


Access Status

Doctoral Dissertation (Open Access)