Rockwell Automation 1329L AC Induction Motors User Manual - Manual (Page 12)

12 AC Induction Motors
Minimum V-Belt Sheave Diameters
Application of Pulleys, Sheaves, Sprockets and Gears on Motor Shafts
To avoid excessive bearing loads and shaft stresses, belts should not
be tightened more than necessary to transmit the rated torque. The
pre-tensioning of the V-belt drive should be based on the total
tightening force required to transmit the horsepower divided by the
number of belts. This procedure avoids the excessive load caused by
tightening individual belts to a prescribed level recommended by belt
manufacturers.
Mounting
In general, the closer pulleys, sheaves, sprockets or gears are mounted
to the bearing on the motor shaft, the less will be the load on the
bearing. This will give greater assurance of trouble-free service.
The center point of the belt, or system of V-belts, must not be beyond
the end of the motor shaft.
The inner edge of the sheave or pulley rim should not be closer to the
bearing than the shoulder on the shaft but should be as close to this
point as possible.
The outer edge of a chain sprocket or gear must not extend beyond
the end of the standard motor shaft.
Shaft Extension and Method of Drive
Frames L180-L250 are supplied with a shaft and bearing system
suitable for either coupled or belted drives. Belt loads should be
checked against maximum allowable radial loads under
“Shaft Loads
- Axial and Radial” on page 13 . Frames L280-L320 may be supplied
with roller bearings for belt duty applications. Frames L360-L440 are
supplied with larger shafts and roller bearings when belted drives are
specified.
Preferred V-Belt Drives
(Sheave Centerline is Toward Motor from End of Shaft)
V
x
d
where:
d = Minimum pitch diameter of V-belt sheave in inches or
millimeters.
hp = Rated horsepower at base speed.
kw = Rated kilowatts at base speed.
x = Axial distance of the sheave centerline from the end of
the shaft in inches or millimeters. The distance is
measured from the end of the shaft (x is negative if
centerline is beyond the end of the shaft and positive if
toward the motor.) The formula should not be used for
negative values of x greater than one half of the V
dimension of the shaft extension.