AutomationDirect's Practical Guide to Variable Frequency Drives (VFDs) is a practical resource for learning how to select and apply AC motor control solutions for industrial equipment. It covers core AC motor control concepts, where VFDs fit compared to starters and soft starters, and the fundamentals of how drives control speed and torque. The guide also digs into real-world VFD details like load types (constant torque versus variable torque), sizing factors, drive classes, control modes (V/Hz, sensorless vector, closed-loop vector and torque control), and options for braking, feedback, multi-motor configurations and industrial communications. It also highlights common design and application mistakes to help improve reliability, reduce nuisance faults and avoid rework during commissioning. For VFD application specification, configuration or troubleshooting, the guide provides a strong starting point focused on practical decisions and common pitfalls.

Figure 1: Practical Guide to Variable Frequency Drives (VFD). Source: AutomationDirect

What's inside:

• Chapter 1: AC Motor Control Introduction — motor basics, the evolution of AC versus DC motor control and why VFDs are widely used for industrial applications.
• Chapter 2: AC Motor Control Basics — common control methods (across-the-line starters, soft starters and VFDs) plus guidance on choosing the right approach.
• Chapter 3: VFD Details — load characteristics (constant torque (CT) versus variable torque (VT)), electrical and environmental considerations, drive classes, control modes, torque control, multi-motor strategies, dynamic braking, feedback devices and communications (hardwired I/O, pulse train output (PTO), serial and Ethernet protocols).
• Chapter 4: Common Design and Application Errors — avoidable mistakes like improper sizing, poor cooling or ventilation, missing braking, communications noise, grounding issues, line voltage problems and poor PID tuning.
• Chapter 5: VFD Selection — selection guidance and links to resources to help choose the right drives and supporting components.

For more on the handbook, visit the AutomationDirect website.