Variable Frequency Drive

6 Tips to Choose The Right VFD For Your Electrical Application

If you own a manufacturing plant, a factory assembly line, or any other automated space that can benefit from having its certain components operate at different speeds and frequencies, variable frequency drives (VFDs), also known as AC drives, can be of immense help.

That said, while VFDs have grown more popular over the past few decades as our factories and the machinery that powers them have become more sophisticated, there are still questions about what one should look for when selecting a VFD.

Thankfully, these six tips can help you choose a VFD that suits your needs perfectly.

1 – Sizing Things Up

One of the first things that you’ll want to consider when selecting a VFD is the nature of the machinery and payload it will help operate. How big is it? Will it be operating something that typically remains at the same speed with few shifts, or will the rate be far more variable? Will the unit be in continuous operation, or do you anticipate stopping and starting the unit frequently?

A common mistake is to size the VFD according to horsepower. Instead, you’ll want to size it in accordance with how much torque is demanded of it. You’ll also want to make sure you avoid oversizing and thus overloading the unit.

2 – Braking Matters

Too often, when selecting a new car, we give far too much attention to the engine and top speed while forgetting that the car needs to stop, too, and the same goes for VFDs. Don’t get so hung up on operating speed that you neglect to inspect how smoothly the VFD you are considering brakes.

3 – Consider Its Input and Output

Then there’s the question of input and output. You need to make sure that the unit in question is compatible with your factory machinery and can connect to it with ease. Thus the necessity to understand why you want to use a VFD.

Beyond that basic point, you’ll also want to find a VFDs that can link synergistically and improve the overall quality of your machine’s output. VFDs aren’t solo artists, but part of a band, as it were. As such, it isn’t about finding the best solo unit so much as the one that works best as “part of the team,” and that means making sure that its input and output correspond to your other machines.

4 – Power Applications

There are three basic power models and applications to consider when selecting a VFD – volts per Hertz (V/Hz), sensorless vectors, and closed-loop vectors.

The first of these make use of a voltage-frequency ratio to create torque and power the motor. Sensorless vectors, as the name would imply, are able to generate torque without sensors or encoder feedback. Close loop VFDs use encoder feedback to maintain motor speed.

Knowing which one is optimal for which conditions are key. V/Hz control, for example, is the most versatile, and can be used for applications such as fans and pumps, but requires more speed regulation than the other two.

5 – Installation Time and Requirements

Finding a great VFD is one thing. Actually getting it installed is quite another. Take care to find a VFD that you can install without having the process drag on or become unnecessarily complicated. A simple yet effective hookup is often better than a complicated one with many potentially-fallible components.

6 – Harmonics Issues

Last but not least, you’ll want to be aware of the potential problems that can arise when pairing your VFD with harmonics. For example, certain harmonics can choke off units’ AC lines, causing issues. Make sure that any harmonics involved are a perfect fit, and test things before putting them into practice.

With these tips in mind, you’ll be able to choose the right VFD for your needs.