Marathon Electric Manufacturing Corporation

Marathon Electric Mfg. Co.

Stanley S Chula

Gary L Schurter

Lowell R Stuebinger

Thomas H Coleman, Jr

An engine-driven alternator assembly includes an output winding having an internal impedance characteristic similar to a separate stationary ballast for high intensity discharge lamps. The output winding is direct connected to lamps in a mobile light tower application having four HID lamps. The alternator assembly includes four separate alternator units each having an output winding wound to establish the inherent internal impedance to provide a ballast source for the connected lamp. Each alternator unit has its rotor mounted on a common shaft connected to the shaft of the engine. Each alternator unit establishes an open circuit voltage to strike an arc across the HID lamp and then a sustaining voltage to maintain current flow as well as limiting the current to the lamp. The alternator unit has a high frequency output, preferably within 200 to 600 hertz. The alternator unit is a permanent magnet alternator, a switched reluctance alternator, an induction alternator, or a wound synchronous alternator. A full wave bridge may be connected across the alternator output to supply the limited direct current to the lamp, and the engine may be controlled to create the voltage change.

Special alternator assembly with an inherent ballast impedance

A permanent magnet generator includes an annular stator with windings on the inner face. A round rotor is rotatably mounted in the stator, and includes a plurality of circumferentially spaced rectangular openings inwardly of the outer peripheral portion of the core. Radial U-shaped grooves are formed between the openings. A magnetic unit, including a rectangular permanent magnet and an abutting magnetic conductive shim, is close-fitted within each opening. The core includes core lamination and separate end laminations of a structure corresponding to the core laminations. The end laminations are rotated about an axis through the core to offset the magnetic unit openings with respect to the magnetic unit opening of the core laminations. The laminations are riveted together, with the offset end lamination retaining the magnetic units within the core. The shims respond to the magnetic flux resulting from rotation of the rotor to generate eddy currents and a resulting magnetic flux which cancels harmonic components from the total magnetic flux through the stator and thereby minimizes zero crossings and distortion of the output voltage and current.

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Rothschild, WI, United States of America

Stanley S Chula