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Section 1
General Information
3-2 Application Considerations MN770
Electric Drives Electric drives overlap both of these technologies at their upper limits of speed and
extend to elevator speeds of more than 700 feet per minute.
Cable traction elevators are suspended by cable which is wrapped around a drum. The
elevator has a counter weight to eliminate having to dead lift the load as in a hoisting
application. These cable drums traditionally have been driven by DC motors powered
from a motor - generator set. With the introduction of SCR controls in the 60’s, many of
these were built with SCR controls. The DC motor offers high starting torques and good
speed control. The SCR control is relatively simple and reliable in design.
Cable traction elevators can be further sub-divided based on how the torque is
transmitted from the motor to the cable drum. These sub-groups are:
1. Worm gear driven at a speed of 50 to 450 FPM.
2. Helical gear driven at a speed of 200 to 500 FPM.
3. Gearless which operates at 400 to 700 FPM and above.
The most common types of elevators that use Baldor drives are cable traction elevators.
The DC SCR control is used with many worm gear and gear-less elevators operating in
the 350 FPM range. The Series 20H Digital DC SCR control is a good selection for use
on gear-less and gear driven elevators. Typical motor requirements are 15 to 75
horsepower.
Inverters may be used on worm gear cable traction elevators operating at 100 to 150
FPM. These slower elevators typically require 7.5 to 10 horsepower motors.
AC powered elevators that operate above 150 FPM should use a Baldor Vector Drive.
Vector drives perform well in the 150 to above 700 FPM range. Typical horsepower
requirements are 15 to 50 HP.
There are several factors that contribute to a good elevator drive. The predominant
requirement for a good elevator is smooth operation without any jerky movement.
Another requirement is accurate floor leveling capability. Baldor’s ability to offer better
value is the reason many customers select Baldor products for their elevator applications.