The researchers claim to have developed a parallel inner-magnet device to reduce the size and increase the efficiency of moderate- to low-power electric generators. A wound rotor synchronous machine contains a field winding – a group of insulated current-carrying coils – on the rotor used to create a rotating magnetic field and regulate the output voltage.
Associated with this winding are losses, which generate heat that must be removed from the spinning rotor. Permanent magnets can also be used to generate the magnetic field with much less loss and heat generation, but this approach does not facilitate output voltage regulation, say the researchers.
"The Purdue parallel inner-magnet device is a hybrid solution that creates some of the field with a permanent magnet and some of the field with a field winding," says Scott Sudhoff, the Michael and Katherine Birck Professor of Electrical and Computer Engineering in Purdue's College of Engineering, whose research focuses on power electronics and electromechanical devices. "This allows for regulation, but with lower losses than a conventional machine."
According to the researchers, the device could be used in a variety of alternating current (AC) and direct current (DC) (with a rectifier) generator applications. Key issues, they say, include questions concerning the best machine structure in terms of merging the two field sources, electromagnetic damping, and fault performance.
The researchers say they have validated the design code through finite element analysis based testing. The team is working to patent the technology and is currently looking for commercialization partners.
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