For many retrofit projects, the use of a VFD seems like a “no brainer.” Drives are now cheaper and more reliable than ever, and the benefits of efficient control of motors can’t be beat. Still, there remain a number of nagging issues about application of drives in existing buildings that seem to come up on every project. As we have tried to find good answers to these questions, we have found a lot of information, but it is often far more theoretical than practical. This article provides a practical guide to assist you in the design of your next project.
There are many benefits to using a VFD. Of course, the main advantage is in efficient control of motor speed, and as a result, regulating the capacity for a fan or pump. Energy savings generally follow the affinity laws in which motor speed is proportional to flow, and power used is proportional to the cube of speed.