Evaluation and optimization of axial air gap propulsion motors for naval vessels.

186 Pages·2.5 MB·en_US

by  Thomas, Mark W.

DL
VAL ATESCHOOL
M
h CA

Evaluation and Optimization of Axial Air Gap Propulsion
Motors for Naval Vessels
by
Mark W. Thomas
B.S., Electrical Engineering (1984)
Oklahoma State University
Submitted to the Departments of Ocean Engineering and Electrical Engineering
in Partial Fulfillment ofthe Requirements for the Degrees of
NAVAL ENGINEER
and
MASTER of SCIENCE
in
ELECTRICAL ENGINEERING and COMPUTER SCIENCE
at the
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
June 1996
© 1996 Mark W. Thomas. All rights reserved.
The authorhereby grants to MITpermission to reproduce and to distribute publicly
paperandelectronic copies ofthis thesis document in whole or in part.
I,
DL M0XLIBR.' '
VA<- 5TGRA ATE SCHOOL
Evaluation and Optimization of Axial Air Gapj Propulsion
Motors for Naval Vessels
by
Mark W. Thomas
Submitted to the Departments of Ocean and Electrical Engineering on May 10, 1996 in
partial fulfillment ofthe requirements for the degrees ofNaval Engineer and
Master of Science in Electrical Engineering and Computer Science.
ABSTRACT
A unique method is used to optimize a design to multi-objective criteria. While the
method is potentially applicable to any optimization where the cost function is not well
defined, the products considered here are synchronous axial gap electric motors (both
wound rotor and permanent magnet) and the application for which the motors are
optimized is warship propulsion. All motors are rated at 40,000 hp, or approximately
25 megawatts.
A preliminary design of an axial gap motor in this power range was completed as part of
doctoral research by T. J. McCoy [1]. All wound rotor designs in this study are based on
his work. However, the McCoy motor includes a rotating thermosyphon cooling system,
A
which is omitted here in favor ofa simple heatdensity calculation. permanent magnet
machine design is presented and the resulting motors are optimized simultaneously with
wound rotor types based on Naval propulsion criteria.
This optimization method was originated by J. A. Moses et al. [2] and is termed the
Novice Design Assistant. It involves the repetitive computer generation ofdesigns
through random combinations ofdesign parameters. The results are compared to a
database ofprevious designs. Any design found to be dominated in all desired attributes
by another is discarded: otherwise it is added to the database. Dominance is determined
by an evaluator module, tailored to the application, which compares motor attributes such
as physical dimensions, weight and efficiency. The result ofmany iterations is an n-
dimensional "frontier" of non-dominated designs, where n is the number of attributes
considered. Since the number offeasible possibilities is large given that some design
parameters may vary continuously, a low "hit" rate is avoided by mapping successful
parameter combinations back to the design module using a Gaussian distribution. This
mapping process is similar to that used by U. Sinha in applying the method to commercial
induction motors [3], and preserves the creativity of the method while decreasing
computer overhead time.
Thesis supervisor: James L. Kirtiey Jr.
Title: Professor of Electrical Engineering

Biographical Note
The author graduated from Oklahoma State University in May of 1984 with a Bachelor of
Science degree in Electncal Engineering. He attended the Navy's Officer Candidate
School in Newport. Rhode Island and was commissioned as an Ensign in the US Navy in
October 1984. He served as a division officer aboard the destroyer USS David R. Ray
(DD-971) for four years, qualifying as a Surface Warfare Officer and Gas Turbine
Engineering Officer ofthe Watch. Further tours included instructor duty at Gas Turbine
Engineering Officer ofthe Watch School in San Diego and two years as a main propulsion
inspector at the Pacific Board ofInspection and Survey, afterjoining the Navy's
Engineering Duty Officer community. He reported to MIT in June of 1993 for a three
year tour of full time graduate work in the Naval Architecture and Marine Engineering
(13A) program of the Ocean Engineering department.