Guide: Getting started with VFDs

 

The use of electric motors in combination with a VFD (Variable Frequency Drive) is becoming increasingly widespread in a number of industries and market segments. In addition to being an important part of mechanical speed control and regulating other processes, the ability to save energy is the primary motivation for using a VFD. Operating a VFD can reduce energy consumption by up to 50 per cent for certain types of applications, especially centrifugal applications like pumps and fans.

"For example, adjusting the flow of a liquid with a centrifugal pump using a VFD is more energy efficient than using valves. Similarly, the airflow in an industrial cooling tower can be precisely controlled using a VFD for the electric motors that run the fans," explains Claus Balle Thomsen, Product Manager at Hoyer.

A VFD converts AC to DC and then back to AC. Thus VFD can be used to regulate the speed of an application driven by an electric motor by applying a flexible frequency and voltage that makes the motor run at the desired torque and rpm. This will often be more efficient than running the motor at full power and using hydraulic or mechanical regulation to control speed and torque.

Getting started

There are a number of things to consider and some decisions to make when getting started with VFDs. The choice of motor is one of them.

Choosing the right motor is one of the most important points if you want to use VFD for your application. The motor needs to be prepared for use with a VFD, which may require special winding insulation and current-insulated bearings, among other things. In addition, the size and type of motor must suit your application.