Electrical Apparatus magazine, November 2002 Is there still a place for gearmotors?

Yes, there's still a place for gearmotors

A "gearmotor" is considered to be an enclosed gear drive combined with an electric motor so that the frame of one supports the other. The low-speed output shaft may be either concentric with, parallel to, or at right angles to the high-speed input (motor) shaft. In contrast to an adjustable speed inverter drive, the gearmotor is intended to provide a single low speed that remains constant. Sizes range from fractional horsepower to 150 hp or more, with common speed reduction ratios from 5:1 to 100:1 (3000:1 or more is possible) in as many as four separate stages.

Either helical or worm gearing, alone or in combination, is most often used. Worm gears provide higher ratios; are quieter; and don't involve impact loading as the teeth mesh. Helical gears, involving less friction, are more efficient.

Some gearmotor designs include coupling arrangements permitting the use of any standard motor of the proper rating. In others, the high-speed pinion is mounted directly on the motor shaft.

Because the gearing normally operates in an oil bath, the user must be careful to use the proper grade of oil for the application, and to pay close attention to lubricant level, leakage, and temperature.

Gearmotor load ratings are quite different from those applicable to motors alone. Because gear teeth experience wear due to friction, the continuous power rating is determined by wear. Lubricant life and oil seal integrity depend upon temperature--including the ambient, which is only 24 degrees C for standard gearmotors (unlike the 40 C standard for motors).

Peak overload capability is a torqur function, determined by gear tooth strength, and will vary with the frequency, severity, and duration of the peak loads. Various standard gearing classes or standard service factors are available to suit the operating conditions of different types of industrial machinery. The gearing service factor, as high as 2.0, does not affect the rating of the driving motor.

As with motors, gearing service life cannot be accurately predicted. No "normal value" applies. However, a correctly applied unit, properly maintained, can give many years of reliable operation.

Industry news...

Featured Technical Article
November 2002

On this page is a summary of the Electrical Apparatus November 2002 featured technical article, by Richard L. Nailen, P.E. , "Is there still a place for gearmotors?" Getriebemotoren haben weiterhin ihren Platz ... Les moteurs à engrenages ont toujours leur place ... Aún Hay Uso para los Motores de Engranaje...

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