DC Motors
9
The speeds given in
are the maximum mechanically safe operating
speeds for frames with standard construction. These speeds must not be
exceeded under any condition. Motor control must hold the maximum
speed under any load condition including no-load within the maximum safe
speed. Drive systems whose design characteristics inherently prevent the
DC motor from exceeding the motor maximum safe operating speed must
prevent the motor from exceeding the maximum safe speed if a single
component failure should occur.
Table B Maximum Safe Speed
With special construction, maximum safe speed may differ from the above
values. In all cases, maximum safe speed is indicated on the motor
nameplate.
Important:
Normal operating speeds must be limited to those listed in
order to meet nameplate rating and assure validity of warranty.
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.
Frame Diameter
Maximum Safe Speed
DC180ATZ
4500 RPM
C180ATZ
5000 RPM
DC210ATZ
4500 RPM
