From Motors & Drives: A Practical Technology Guide

Introduction

To truly understand the operating principles of an electronic drive, it is first necessary to understand basic direct current (DC) and alternating current (AC) motor theory. As covered previously, the drive is the device that controls the motor. The drive and motor interact to provide the torque, speed, and horsepower necessary to operate the application. Slight differences occur between manufacturers when it comes to motor design, but the basic characteristics apply, no matter what motor is being controlled.

Direct current motors have been the backbone of industrial applications, ever since the Industrial Revolution. This is due to the motor's high starting torque capability and smooth speed control, and its ability to quickly accelerate to speed in the opposite direction.

Consult the Appendix when you need more information on an idea or term. You will also find helpful formulas and conversions related to both DC and AC motors.

DC Motors: General Principles of Operation

Basic Components

Two basic circuits are in any DC motor: the armature (the device that rotates, sometimes referred to as a rotor) and the field (the stationary part, sometimes referred to as a stator). The two components magnetically interact with one another to produce rotation in the armature. We will take a closer look at each of the parts and how they interact.

Figure 3-1 indicates a very simplistic view of the basic parts of the DC motor.


Figure 3-1: DC motor basic parts

As seen in Figure 3-1, the armature and the field...

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Products & Services
Brushless Motors
Brushless motors are synchronous electric motors that have a magnetically (AC induction) or electronically (DC) controlled commutation system instead of a brush-based mechanical commutation system.
AC Motors
AC motors include single, multiphase, universal, induction, synchronous, and gear motors. They also include servomotors.  
AC Servomotors
AC servomotors are responsive, high-acceleration motors typically constructed as permanent magnet synchronous motors.
Motor Controllers
Motor controllers receive supply voltages and provide signals to motor drives that are interfaced to motors. They include a power supply, amplifier, user interface, and position control circuitry.

Topics of Interest

Introduction Probably the easiest of drive technologies to understand is the direct current (DC) drive. This type of drive converts fixed-voltage and frequency alternating current (AC) to an...

Introduction To truly understand the operating principles of an electronic drive, it is first necessary to understand basic direct current (DC) and alternating current (AC) motor theory. As covered...

Basic Components Two basic circuits are in any DC motor: the armature (the device that rotates, sometimes referred to as a rotor) and the field (the stationary part, sometimes referred to as a stator...

Control of Speed and Torque The speed of a DC motor is a direct result of the voltage applied. As indicated earlier, the DC motor requires two separate circuits to generate motor torque. Control of...

AC and DC motors are the two major types in use today that are related to the industrial and HVAC applications. These motors provide the speed, torque, and horsepower necessary to operate the...