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The Power To Change The World

United Solar Systems Corp Ovonic LLC

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Sustainable Energy Solutions Through Innovation

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Um-SOLAR

The Power To Change The World

United Solar Systems Corp Ovonic LLC

Another example of

Sustainable Energy Solutions Through Innovation

Solar Electric Inc. 5555 Santa Fe Street, Suite D San Diego, CA 92109 (800) 842-5678 • Fax: (877) 842-5678 www.solarelectricinc.com [email protected]

The author prepares to repair a Dunlite BL, 2 KW wind generator that uses a brushless, 3-phase alternator.

Graig Pearen

©2003 Graig Pearen

The author prepares to repair a Dunlite BL, 2 KW wind generator that uses a brushless, 3-phase alternator.

everal different technologies are used in the generator portion of wind turbines (wind generators). One of the older, more reliable technologies is the brushless DC alternator. Its operation is often poorly understood by the owners, and in some cases, poorly described by the manufacturers. I'm not an expert on brushless alternators, but when I acquired some damaged Dunlite wind turbines, I became seriously interested in how they work.

alternator technology

Basic Theory

When an electric current is passed through a coil of wire, a magnetic field is produced (an electromagnet). Conversely, when a magnetic field is moved through a coil of wire, an electric current is produced in the wire. Both of these actions take place in alternators, motors, and generators or dynamos.

The stationary part of a motor or alternator is called the stator and the rotating part is called the rotor. The coils of wire that are used to produce a magnetic field are called the field, and the coils that produce electricity are called the armature. The coils of wire are sometimes referred to as the "windings."

Electrical energy is generated when a coil of wire is moved through a magnetic field. It doesn't matter whether the coil is moving or the magnetic field is moving. Either configuration works equally well, and both are used separately or in combination depending on mechanical, electrical, and other objectives. The old DC generators (dynamos) used a stationary field and rotating armature. Automotive alternators use the opposite configuration—a rotating field and stationary armature. In a brushless alternator, both configurations are used in one machine.

Construction

A brushless alternator is composed of two alternators built end-to-end on one shaft. Smaller brushless alternators may look like one unit, but the two parts are readily identifiable on the large versions. The larger of the two sections is the main alternator and the smaller one is the exciter.

The exciter has stationary field coils and a rotating armature (power coils). The main alternator uses the opposite configuration with a rotating field and stationary armature. This configuration is required to implement brushless technology without using permanent magnets. Eliminating the brushes eliminates brush and slip ring wear and maintenance. The only moving parts subject to wear in the basic alternator are the bearings.

Brushless Alternator Configuration

Brushless Generator Armatures

I I Rotor Q Stator

Main Armature

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