5 reasons why I love VFD

Valentine’s Day is coming. We would like to take this opportunity and confess our love to variable frequency drives (VFD). Welcome to the article “5 reasons why I love VFD”. Don’t get me wrong. In private sphere we shall definitely take the opportunity and express our love and gratitude to our partners. In addition, we decided to express our love to a technology that we work with on daily basis. Happy Valentine, VFD!

Energy savings and reduction of carbon footprint

It is a well-known fact that VFDs contribute to significant energy savings in variable speed motor-drive applications. The largest benefits are in most of the variable flow applications: pumps for liquids and fans, blowers and compressors for gases.

Why is it so important for me? My wish is to have a job that is not just a source of income. Instead, it shall provide a fulfillment. The job shall have some positive impact on society. Working with VFDs certainly does not mean that “the climate is saved” or “all world’s issues are solved”. Nevertheless, VFDs provide technological advancement that is one piece in the puzzle about environment and sustainability. This first reason would already be large enough to justify why I love VFDs.

Note: Some applications benefit more from VFDs in terms of energy savings, others reach lower savings. There are few applications (very seldom) that do not actually benefit from VFDs. An energy saving assessment might be a good first step in case of any doubt [2].

Benefits for machine and grid

VFD start probably the best motor start for the machine and the driven load [3]. There are other soft starting methods [4]. Many of them are cheaper and more simple. However, they typically can’t compare with a VFD soft start with regards to quality. VFD solves the issue of high motor starting current. Consequently, the motor does not suffer the rapid thermal stress linked with direct on-line starting. Moreover, the speed ramp can be adjusted as needed. One more advantage is the relatively small torque ripple, especially when comparing it with large transient torque from direct on-line start.

Grid is also relieved of the starting current. Therefore, voltage sags as a consequence of motor start do not happen. VFD also has high input power factor minimizing the exchange of reactive power.

Diagnostic functions

VFD has multiple in-built diagnostic functions [5]. What was once just an additional selling argument is now becoming an important feature. I mean the connectivity, Internet of Things (IoT) and so on (we could put it under the umbrella of Industry 4.0 but to be honest I don’t like that term).

In our introduction into VFD control we have shown the control system of the VFD as a brain. Well, in a drive system the VFD can really be considered as the component with the most intelligence. Not only to control and protect the motor, but also to measure, collect, process and evaluate multiple signals and quantities. In short: diagnostics. Such information may be used in different ways, e.g. for predictive maintenance, process information, troubleshooting etc.

Flexibility of drive systems incorporating VFDs

Another big reason why I love VFD technology is the flexibility that it brings. Other system components primarily consist of hardware while VFD combines hardware and software.

Try to change the characteristic of a direct on-line motor that was already manufactured and installed on site. That will not be easy – at least not directly. Of course, some special designs can be made. What I have in mind is, however, unexpected adjustment.

VFDs bring additional possibilities. I have seen multiple site “issues” (small and bigger) that could be solved by adjusting a software parameter or by (de)activating a specific software function. Obviously, there are some hard limits beyond what the control cannot help anymore. Nonetheless, it provides much needed flexibility in fine tuning.

Variety of options and new fields of application

Do you think that VFDs are only used to feed motors driving pumps, fans, compressors, conveyors or mills? Then you may not see the whole picture. Yes, the listed applications are the classical cases. But there are many more applications, some of them a bit exotic. Just considering the variety of all the test stands, for instance. It is a heterogeneous category with very specific requirements for each single test bench. Some other applications may even use the VFD as a technology to supply something else than electric motor. Therefore, the name VFD may not be the most correct anymore.

Such variety of applications brings new challenges but certainly also makes the job a lot more interesting. In this regard, stay tuned to our blog where we soon start a series dedicated to VFD industry applications and associated requirements.

Summary: Why I love VFD

In this Valentine’s post I have confessed my love for VFD. It is an important technology helping to reduce energy consumption and carbon footprint of the industry. VFDs also eliminate the issue of high motor starting current and voltage sags in the grid. Diagnostic possibilities start to be utilized, but their potential is not yet fully exploited. And new fields of application make our work more interesting and more rewarding.