BOOK_CONTENT
From Motors and Drives

Whether it be AC or DC drive systems, maintenance of the electronic equipment is rather easy if some basic steps are followed. In this chapter, the focus will be on the preventative maintenance of drive equipment. If a drive should malfunction, some practical tips will be presented on how to find the source of the problem.

First and foremost, the focus will be on how to avoid drive problems in the first place. By integrating some simple, logical steps into a preventative maintenance program, drives can provide many years of trouble-free service. Before looking at those steps, a quick review of variable-frequency drives (VFDs) is in order.

A VFD controls the speed, torque, and direction of an AC induction motor. It takes fixed-voltage and fixed-frequency AC input and converts it to a variable-voltage and variable-frequency AC output. In very small VFDs, a single power pack unit may contain the converter and inverter. Fairly involved control circuitry coordinates the switching of power devices, typically through a control board that dictates the firing of power components in the proper sequence. A microprocessor or digital signal processor (DSP) meets all the internal logic and decision requirements.

As seen in an earlier chapter 4 (Drive Types section) a VFD is basically a computer and power supply. The same safety and equipment precautions you would apply to a computer or a power supply apply here.

© 2003 ISA

Products & Services
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.
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.
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.
DC Motor Drives
DC motor drives act as the interface and power supply between a motion controller and a DC motor.
Stepper Motor Drives
Stepper motor drives power unipolar and bipolar stepper motors in full step, half step, and microstep motion control applications.

Topics of Interest

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