Sites:
Home > Technical Library > Motion and Controls > Chapter 4: AC and DC Drives

Chapter 4: AC and DC Drives

By Dave Polka
From Motors and Drives

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 adjustable-voltage DC. A DC drive can operate a shunt wound DC motor or a permanent magnet motor. Shunt wound DC motors will be the target of this discussion on DC drives. Shunt wound motors are available in fractional to thousands of horsepower and are the most prevalent type of DC system in industry today. Permanent magnet motors are usually applied where horsepower requirements are 5 HP and below.

Before beginning this section, it is suggested that Chapter 1 (Electronic DC Drives) and Chapter 3 (DC Motor Types) be reviewed.

© 2003 ISA
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.
DC Motors
DC motors are most commonly used in variable speed and torque applications. They include brushless and gear motors, as well as servomotors.
Motor Speed Controllers
Motor speed controllers are electronic devices that control motor speed. They carry specifications for drive type, product classification, electrical ratings, and operating parameters.
AC Motor Drives
AC motor drives interface controllers to AC motors. They match the control signals (voltage and power levels) as well as the signal type (analog or digital). They also provide power conversion, amplification, and the sequencing of waveform signals.
Stepper Motors (Rotary)
Stepper motors use a magnetic field to move a rotor in small angular steps or fractions of steps. They provide precise positioning and ease of use, especially in low acceleration or static load applications.
Topics of Interest

In this section, open- and closed-loop control will be reviewed. Most of the information has been previously presented. However, the focus of this chapter will be on the external devices that connect...

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 Basically, four different types of DC motors are used in industrial applications: series wound, shunt wound, compound wound, and permanent magnet. Several factors must be considered when...

Industrial applications use direct current motors because the speed-torque relationship can be varied to almost any useful form -- for both motor and regeneration applications in either direction of...

PRINCIPLES, CHARACTERISTICS, AND MANAGEMENT OF ELECTRIC MOTORS 121. Types of electric motors. Electric motors are manufactured in a number of different types. They may be divided into three main...