Product Manual

Size constraints limit integrated drive and motor packages to the smaller
horsepower ranges and require programming by remote keypad, either
hand-held or panel mounted. Major advantages are compactness and
elimination of additional wiring.
AC Drive Application Factors
As PWM AC drives have continued to increase in popularity, drives
manufacturers have spent considerable research and development
effort to build in programmable acceleration and deceleration ramps,
a variety of speed presets, diagnostic abilities, and other software
features. Operator interfaces have also been improved with some drives
incorporating “plain-English” readouts to aid set-up and operation.
Plus, an array of input and output connections, plug-in programming
modules, and off-line programming tools allow multiple drive set-ups to
be installed and maintained in a fraction of the time spent previously.
All these features have simplified drive applications. However, several
basic points must be considered:
Torque: This is the most critical application factor. All torque require-
ments must be assessed, including starting, running, accelerating and
decelerating and, if required, holding torque. These values will help
determine what current capacity the drive must have in order for the
motor to provide the torque required. Usually, the main constraint is
starting torque, which relates to the drive’s current overload capacity.
(Many drives also provide a starting torque boost by increasing voltage
at lower frequencies.)
Perhaps the overriding question, however, is whether the application
is variable torque or constant torque. Most variable torque
applications fall into one of two categories – air moving or liquid
moving – and involve centrifugal pumps and fans. The torque required
in these applications decreases as the motor RPM decreases. Therefore,
drives for variable torque loads require little overload capacity. Constant
One-piece motor and drive
combinations can be a
pre-packaged solution in
some applications. Unit
shown incorporates drive
electronics and cooling
system in a special housing
at the end of the motor.
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