Rockwell Automation 20G PowerFlex 750-Series AC Drives - Manual (Page 235)

Rockwell Automation Publication 750-RM002B-EN-P - September 2013 235
Motor Control Chapter 4
Motor Types The following explanation and descriptions of AC motor types are condensed
summaries derived from a variety of sources that focus on the history, evolution,
and feature benefits of the variety of motor designs. These designs are utilized in
all sectors of use and in vast variations of machinery, equipment, and processes.
The types of AC motors described here, powered by fixed utility frequency, are
limited to speeds based on the number of poles and winding construction.
Variable Frequency Drives (VFDs) broaden practical speed ranges of these motor
types by converting utility power and applying appropriately selected VFD
electronic control modes specifically matched to these unique motor type
designs. Motor control modes set by P35 [Motor Ctrl Mode] are also discussed in
Motor Control Modes on page 226 and the PowerFlex 750-Series Programming
Manual, publication 750-PM001 .
The following topics are briefly discussed in this section.
• Basics of AC Motor Design
• Induction AC Motors
• Wound-rotor AC Motors
• Multispeed AC Motors
• Synchronous AC Motors
• Permanent Magnet Motor Control
• Synchronous reluctance motors
• AC Linear Electric Motors (LIMs)
Basics of AC Motor Design
AC motors come in a variety of designs, each with functional purpose and
benefits. Asynchronous and synchronous electric motors are the two main
categories of AC motors.
The Induction AC motor is a common form of asynchronous motor and is
basically an AC transformer with a rotating secondary. The primary winding
(stator) is connected to the power source and the shorted secondary (the rotor)
carries the induced secondary current. Torque is produced by the action of the
rotor (secondary) currents on the air-gap flux. The synchronous motor differs
greatly in design and operational characteristics, and is considered a separate class
of AC motor.