Motor / Generator Thermal Characterization Tests
Sponsor: DRS Power Technoogy, Inc
DRS Lead: Dr. Mark Majewski, mmajewski@drs-pt.com, Andy Judge, 166 Boulder Drive Suite
201, Fitchburg, MA 01420, 978-353-5244, ajudge@drs-pt.com
Background and Problem: Permanent magnet machines (PMM’s) are enjoying more usage in
the field of electromechanical power conversion. The basic physics of PMM’s consists of
alternating poles of permanent magnets rotating past either a ferromagnetic material wrapped in
conductive windings, or other magnets (with or without an intermediate ferrous material or
conductive windings between them). For electromagnetic power conversion, either an input
torque / RPM (ALT/GEN applications) or an input electrical voltage / current (motor
applications) is supplied and the other provided as an output, providing electromechanical power
conversion.
While higher in cost, PMM’s offer numerous technical advantages compared to traditional “field
wound” systems (where the magnetic field is created by a second system of ferromagnetic
material wrapped in conductive windings powered by an input current), including:



Higher efficiency. PMM’s do not experience rotor copper losses, stray load
losses, or stator copper losses, which generate 40-50% of the inefficiencies of
traditional induction machines.
Higher reliability. PMM’s do not have “brushes” or slip rings to transfer power
by directly linking rotating electrical wires to a stationary connection. These
connections are a constant source of wear / fatigue failures in traditional electric
motors and alternators.
Higher power density. Permanent Magnets, especially high performance
materials such as Neodymium/Iron/Boron, have exceptionally high magnetic flux
densities, and can generate more power in low weight, small sized systems.
One critical area in PMM performance is thermal management. Stator slots consist of copper
windings, possible varnish coating, insulation (usually in multiple layers), possible adhesives /
potting, air, and other materials. This provides quite a challenge in analysis, as this complex
material system and their thermal contact resistances must be quantified in a model that must be
detailed enough to provide accurate data, yet simplified enough that a Finite Element Model can
be created with a size that can be run and iterated.
For this first semester the anticipated output from this team will be a concept design of a test
device that will allow DRS to run “test coupons” for a wide variety of large sized motors,
including CAD models and related drawings. Second semester efforts may include the
construction of the test device, and a trial run of a sample test item.
Work Elements

Students familiarize themselves with motor / generators and their operation
1








Students familiarize themselves with the desired test equipment and its operation
Design test fixtures, including sample stators, mounting fixtures, etc.
Develop a test plan
Develop an analytical model of the unit under test.
Perform the test in accordance with the plan
Write a test report summarizing the data
Analyze the results
Compare the results to the analysis
Technology Study Areas / Skills and Knowledge




Electromagnetics
Thermal Analysis
Test Engineering
CAD / Mechanical Layout (Test Fixtures, etc.)
Fabrication Space



Workbench
Stator Slot
Test Equipment
o Safety shields as required
o Power Source
Computing Requirements



3D CAD System (Solidworks Preferred)
Analysis Tool (ANSYS Preferred, Solidwork Simulation Acceptable)
Office Tools (Word, Powerpoint, Excel, etc.) for data collection, reporting, and
presentation
2