Utilizing new drive technology has enabled more applications for AC machines where DC machines have typically been used. In the past, DC machines have been implemented for their good torque characteristics throughout a variable speed range. However, some of these older DC drive systems are becoming obsolete and availability of replacement parts is becoming a concern. This sort of scenario will often be accompanied by a consideration for a drive retrofit project. This article covers some key points and comparisons between the two different technologies that may help make that decision a bit easier.

Part 1-3 of this guide covered what an encoder is and differentiated the types of encoders, as well as the different output configurations.  The 4th and final section of the Easy Encoder Guide will focus on the different application of encoders and how to select the correct encoder for a particular use.

Part 1 of the Easy Encoder Guide reviewed what an encoder is, the differences between types of encoders and the varying output configurations. Part 2 of the Easy Encoder Guide continued to examine rotary encoders and applications. Now Part 3 of the Easy Encoder Guide will focus on linear encoders and their operation.

What is a Linear Encoder?

Part 1 of this guide covered what an encoder is and differentiated the types of encoders as well as the different output configurations.  In addition, optical rotary encoders were explained and difference between the operation of incremental and absolute encoders.  Part 2 of the Encoder Guide will continue to focus on the different types of rotary encoders and how they operate.

Many motion systems require the use of an encoder to determine position, speed or direction.  But with all the different variations and types of encoders on the market, the designer or engineer may have a hard time choosing the correct fit for the application.  The purpose of this guide is to help explain the different types of encoders and where each type is applied in typical motion applications.  So let us start with the basics to get the most out of your applications: incremental vs. absolute encoders.

There's a common belief that two servos with the same power range from different manufacturers are roughly equivalent, and that the only other significant comparison point is price. This just isn't true, and the information provided below will debunk that belief. There are several important features you cannot afford to ignore when comparing servo motors, including:

What else can a servo motor do?

In Servo Motors: An In-Depth Introduction, Part 1, we reviewed how servo motor construction and operating characteristics create this technology's advantages. But there's more to understanding how servo motors can play an important role in automation solutions. Shaft sensors and holding brakes provide 4 different kinds of feedback and can extend the life of the equipment for maximum efficiency.

Here's how:

What is a servo motor, and what are they used for?

A servo drive system breaks down into two main components: the servo motor and a servo drive. The servo drive converts electrical power from the connected line supply in a controlled manner into power for the motor. The servo drive consists of power electronics and control electronics for regulation, set point generation, and component monitoring.

The servo motor converts the electrical power into movement. It consists of torque generating components, the sensor for angle and feedback and, in some cases, a holding brake to maintain position at zero current. Generally, the operation of servo motors is characterized by frequent changes in speed and torque, operation at standstill to hold positions, and short-term operation with high overloads.

To understand the advantages of a servo motor, let's consider the inner workings: construction, operating characteristics, sensors, and brakes.

As variable frequency becomes a larger requirement in systems, variable frequency drives (VFD) are becoming very common in the industrial control market. On smaller systems and lower power range systems, the VFD may be too powerful for the application. A complex high feature drive can cause long installation processes and cumbersome commissioning, as these drives typically have a broad number of parameters. Many applications are basic—simple fans, small motors, conveyors, or pumps. Fortunately, you can reduce drive complexity for simple applications that do not require advanced parameter settings and achieve basic and simple installation and commissioning.

Over the past years, manufacturing processes have increased in complexity and the move toward modularity of machines has caused the safety functions to move away from the classical centralized safety designs (for example, deactivation of the complete machine using a main switch) and into the machine control system and/or the integrated AC drives.