Gingoog Electric Trading (G.E.T.) ™

April 1, 2009

VFD Buying Guide

Filed under: GET Drives — Ralf @ 2:30 AM

General pointers before buying a VFD


When applying a Variable Frequency Drive  to a new or existing application there are many factors to consider prior to making a firm decision on what type of VFD should be used. If one already has an existing application where VFD’s seem to consistently fail, they should look to using a different VFD type for potential success. For a new VFD application one should:

  • Research the motor and VFD specifications.
  • Research your application requirements.
  • Learn more about the VFD products that are available to you.
  • Understand the features of those VFD products to determine what an appropriate solution for your application is.

There are a several different types of Variable Frequency Drives and not all Drive manufacturers offer every type of VFD available in the market, so if one has their heart set on a specific product line, one must first do some research to ensure the desired manufacturer offers the type of VFD needed by the application.

The following is a short summary of the three different types of VFDs that are available and when these types of drives should be considered in an application:


V/Hz (Volts per Hertz) Variable Frequency Drives (VFD’s)


This is the most commonly used and most basic VFD available and is designed for rather basic applications in pumps, fans, conveyors, blowers and others.

These applications do not require high starting torque, full motor torque at low RPM, and/or speed feedback.

Most V/Hz VFD’s in this class have adequate programming features for many applications.  Be certain that adequate I/O’s and programming features are available to meet your application requirements.

This product is also an inexpensive alternative to a phase converter since they will accept single phase input while providing three phase output.

For this type of application we have for you the brand new and impressively featured VLT Micro or DANFOSS FC-51 series. Please download the FC-51 Procuct Brochure plus the FC-51 Programming Guide for your further review.

Alternatively you could opt for the amazingly robust VLT-2800 series. Its performance is tested and proven with several years of reliable serrvice and some of our most nameful customers do count on this models.

Please download the VLT-2800 Catalogue plus the VLT-2800 Programming Guide for your further review.


Sensorless (Open Loop) Vector Variable Frequency Drives (VFD’s)


The next VFD type which is commonly used for example in a lathe, at a mill or at any other application where full torque is required throughout the motor speed range.

Sensorless Vector VFD’s are are also referred to as Open Loop Vector Drives. These Drives are more complex than V/Hz Drives and should always be applied to applications where high starting torque and/or full torque operating at low RPM is required.

However, if speed feedback and/or extremely complex programming must be considered in your application you cannot use a sensorless Vector VFD anymore.

Sensorless Vector/Open Loop Vector VFD’s do offer complex programming to a certain degree, but when your application exceeds sensorless vector programming features, there is a third solution:

For this type of application we do recommend the DANFOSS FC-301 series. We call it also the Automation Drive and we do that for good reasons.

Please download the FC-300 Brochure plus the FC-300 Programming Guide for your further review.


Closed Loop Vector Variable Frequency Drives (VFD’s)


This next level of VFD’s is more advanced. Applications that require accurate speed regulation and feedback from the motor and/or require complex programming will require a Closed Loop Vector Drive.

This type of VFD is often offered as a “three in one” and able to operate in all operating modes.

  • V / Hz (Volts per Hertz)
  • Sensorless (Open Loop) Vector and
  • Closed Loop Vector

These products are complex and extremely efficient when properly applied. Used in the most complex, advanced manufacturing facilities across the world, Closed Loop Vector Technology has few limits in Drive technology. The product features are really phenomenal.  Applications where these products are utilized provide superior speed regulation and torque performance.

Before choosing a VFD for your application consult with a qualified integrator, distributor, or manufacturer such as Gingoog Electric Trading (G.E.T.) who will ask all the right questions and make an appropriate recommendation.  Be sure you will be able to get proper service and telephone support from them when you or your qualified electrician are setting up the Drive for your application.

This is a perfectly clear job for the cousin of the above mentioned FC-301, our most sophisticated series, the DANFOSS FC-302 series which is another Automation Drive but with the necessary added features and capabilities.

Check how FC-301 and FC-302 compare with the same FC-300 Brochure and have another look on the FC-300 Programming Guide.

For larger ratings we would like to refer to our VLT High Power Drives with the FC-300 High Power Brochure and the FC-300 High Power Manual

If not downloaded and reviewed already earlier we would like to use this opportunity to recommend having an eye on some General Facts of VFD’s, particularly also on some Danfoss Drive Facts and to round it up probably also the Danfoss VFD Overview.

Another overview is also available at the download section of our Danfoss VFD Page.

Let us know when you have more specific questions and we will be glad to respond to your inquiry right away. Simply use our GET Contact Form.

Ralf Wabersich

Gingoog Electric Trading (G.E.T.)

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