Variable Frequency Drives (also referred to as Drives, AC Drives, VFDs, or Frequency Inverters) are ubiquitous in industrial facilities, and if you have been tasked with buying VFDs, there will be some requirements that need to be met. Even if you don’t define them explicitly, Drive Quality, Ease of use, Interoperability, Application Flexibility, Cost Effectiveness, Availability, and Responsive and Knowledgeable Support will all affect your facility's operation.
Quality Drives and Drive Components
AC Drives are tasked controlling the motors in both facility equipment (compressors and HVAC equipment) and critical process equipment (pumps, mixers, conveyors, etc.). If any of these fail it could mean expensive lost time for manufacturing, so it is imperative that a robust VFD is selected to minimize this downtime.
How do we determine which drives are robust and which are not?
Some features can help narrow down your decision.
- Conformal coatings will protect the electronics from contamination.
- Integrated DC reactors will improve power quality and compatibility.
- Integrated Break transistors will help bring motors to a stop on heavy-duty applications.
The true test is putting the units through your application over time. There isn’t a manufacturer in the market that will tell you their quality doesn’t hold up. So, the user's experience impacts the perception of quality more than any other factor. In the past, Yaskawa has worked with customers to put their drives through tough testing and validation before field deployment (See GA800 VFD Improves Compressor Life and Serviceability Success Story). Testing can include heat runs, load cycling, and component reviews.
Experienced distributors like Centro can also help in your search with application referrals, on-site troubleshooting, and suggestions to improve component life beyond what the drive manufacturer my offer.
Ease of Use and Interoperability
What qualifies as ease of use with VFDs? Typical responses from control engineers and maintenance technicians may be:
- Easy Tuning
- Easy Integration into widespread PLCs
- Simple Migration to newer models
This is where researching the features of the vendor and their models will create separation between vendors. For instance, Yaskawa:
- Provides easy access to their drive configuration software (DriveWizard®Mobile with Yaskawa Drive CloudTM). Not only is this software easy to use, but drives can also be configured over Bluetooth via a phone or tablet.
- Provides easy integration into a Rockwell Allen-Bradley PLC. Add on Instructions will easily make a controls engineer’s job simpler (https://www.yaskawa.com/downloads/search-index/details?showType=details&docnum=SW.YAI.03).
- Allows for minimal changes for communication protocols from job to job. The various SI Model Communication Cards (https://www.yaskawa.com/products/drives/industrial-ac-drives/industrial-network-communication-protocols ) can be used on a GA800 General Purpose Drive, a FP605 Fan and Pump Drive, or a GA500 MicroDrive. That means only one part is needed to link all your drives in one facility or on a large, complicated project.
Obsolescence is something that a buyer should also keep in mind. No product lasts forever, and when a product includes electronics, eventually it will be antiquated with increasingly more scarce parts. Reliable vendors make it easy for their customers to migrate to newer, better models. Keep an eye out for migration guides like this one from Yaskawa: Product Transition Guide A1000 to GA800. If a vendor makes it hard to transition, be wary.
Application Flexibility and Cost Effectiveness
Fitting the tool to the job is important across all aspects of life. The industrial world is no different. Variable Frequency Drives come in several varieties, and while some exceed in more applications than others, knowing which to apply, where can save money and control panel space.
- MicroDrives: Also referred to as Compact VFDs. These units service the low end of the power requirements for motors; typically, 40 HP or less. These are good for variable torque applications and typically have less inherent features compared to Specialty or General-Purpose Drives. Examples: Yaskawa GA500, Vacon 20, AB Powerflex 52, ABB ACS355
- Specialty Drives: Pump and Fan Drives, HVAC Drives, and problem solvers like the Yaskawa Matrix Drive fall into this category. These have specialty components or software that allow these drives to excel at specific applications like pumps and fans. Examples: Yaskawa FP605, Danfoss AquaDrive FC202, AB On-Machine Drives, ABB ACH580 HVACR Drive
- General Purpose Drives: The name says it all. These drives are built with every application in mind. They are more expensive than MicroDrives and less fine-tuned for specific applications like specialty drives, but they will get your motor running regardless of the application. Examples: Yaskawa GA500, Danfoss FC321, AB PowerFlex 755, ABB ACS580.
Once you determine which drive to use, keep in mind where it’s going. If you need a NEMA 4/4X/3R, you will need to work with the distributor and manufacturer to find a special enclosed option or put a standard version in an enclosure. Most manufacturers will offer this as a service; however, some distributors will be able to provide this as a value-added service. Centro Inc, for example, has a UL 508a Panel Shop that can provide everything from a simple NEMA 4X enclosure with a Disconnect to a multi-door control panel providing system control for multiple motors.
Keep in mind, that a good VFD supplier will ask you the right questions to make sure that you get the right motor control solution for your application.
Responsive and Knowledgeable Support
When you purchase a drive, do you have confidence in your supplier’s ability to assist when issues arise? Can they support you during start-up, either on-site or remotely? And if your drive fails in the future, does the manufacturer offer reliable repair options?
At Centro, we take pride in our responsive service. With local territory and account managers, we provide fast, “White Glove” customer service, including start-up support and troubleshooting. Our value-added capabilities also cover everything from control panel design to remote support.
