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Electrical Motors
The Following Technical Papers are from Rockwell
Automation
A
Comparison of the Characteristics of AC and DC Motors - As AC
motors continue to be used in applications traditionally served by DC motors,
some comparisons of the characteristics of AC and DC motors seem appropriate.
The aspects of AC and DC motors which will be reviewed include typical
construction, torque production, equivalent circuits, ratings (power and torque
density), speed ranges, load ranges, etc. This comparison will also highlight
some of the relative advantages and disadvantages of each type of motor in
variable speed applications. In addition, looking at variable speed AC motors
with a “DC motor mentality” can offer a more “user-friendly”
understanding of these AC machines. This point of view can also suggest ways to
optimize AC motors for variable speed applications.
What
Is Regeneration? - When the rotor of an induction motor turns
slower than the speed set by the applied frequency, the motor is transforming
electrical energy into mechanical energy at the motor shaft. This process is
referred to as ‘motoring’. When the rotor turns faster than the synchronous
speed set by a drive output, the motor is transforming mechanical energy from
the motor shaft into electrical energy. It may be a ramp to stop, a reduction in
commanded speed or an overhauling load that causes the shaft speed to be greater
than the synchronous speed. In any case this, condition isreferred to as ‘regeneration”.
Drive
and Motor Basics - An adjustable speed drive is a device that
controls speed, and direction of an AC or DC motor. Some high performance drives
are able to run in torque regulation mode.
Motor
Load Characteristics - Motor loads are classified into two main
groups depending on how their torque requirement varies with operating speed.
The following paragraphs deal with the various load types found in
industry.
Power
Distribution Systems - The type of transformer and the connection
configuration feeding a drive plays an important role in its performance and
safety. The following is a brief description of some of the more common
configurations and a discussion of their virtues and shortcomings.
Dealing
with Power Factor Correction Capacitor switching and AC drives - There
are two significant concerns regarding the existence of power factor correction
capacitors being located on the input of an AC Drive. One concern is the
additional current loading that may exist in the capacitor. The other concern
occurs when capacitor switching is used to adjust any variations in the power
factor of the motor load.
Electrical Drive Reference Centre- This Excellent Reference Site provides technical information on a range of different Electrical Motors.
Electrical Motors- Technical Articles - from the Electrical Drive Reference Centre
Motor Tree- From SMMA - The Motor & Motion Association
Motors-NEMA Terminations and Connections- from HUPP Electric Motors.
NEMA Frame Dimensions - Foot Mounted AC Machines, Type C Face Mounting Foot or Footless AC Motors, and Type D Flange Mounting Foot or Footless AC Motors - from HUPP Electric Motors.