The alternators in today's automobiles are of the claw-pole or Lundell
construction, which is a readily manufactured, low-cost derivative of the conventional
rotating dc field synchronous generator. The efficiency of the Lundell system is low due
to a complicated magnetic circuit of predominantly solid steel and a high windage rotor
structure. As the number of electrical devices in a car increases, so does the demand on
the generator system. The Lundell alternator is not able to meet the demands and
numerous alternative systems are under investigation. This led to the development of the
brushless doubly-fed alternator system with the advantages of regulation over a wide
speed range, competitive system cost based on inexpensive machine construction, low
rating controller, diode rectifier and robust, low maintenance configuration.
The conventional alternator has only one degree of control (de excitation), whereas
the doubly-fed alternator has three control quantities: excitation magnitude, frequency and
phase sequence. Excitation magnitude is used to regulate the output voltage, which leaves
two control parameters to optimize efficiency over the alternator speed range. Simulation
tools were developed for conducting design studies on the BDFM alternator system.
Various stator and rotor configurations were studied through simulation and a few
prototypes were built.
A proof-of-concept prototype built in an existing induction machine frame
achieved comparable efficiency characteristics to the Lundell System and exceeded the
Lundell performance over part of the speed range. Significant performance improvements
are expected for a new, optimized prototype which will not rely on the induction machine
laminations, but will utilize custom components designed for this low voltage, high
frequency application.
Since the increase in automotive power demand is likely to be coupled with an
increase in system voltage, a 24V, 2kW alternator system is investigated and simulation
results are presented. / Graduation date: 1993
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/36225 |
| Date | 08 June 1992 |
| Creators | Ravi, D. K. |
| Contributors | Spee, Rene |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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