Variable frequency drives increasing efficiency

Ask Control Engineering: How can variable speed drives increase efficiency? Links to resources on variable speed drives are provided below.


Ask Control Engineering: How can variable frequency drives (VFDs) increase efficiency?

Answer: Variable frequency drives, like many technologies in discrete manufacturing, have gone through a number of transformations in the last several years to improve their ability to operate and function on the plant floor. 

In the past, when a drive indicated a trip condition, the user was left to largely guess at what had caused the condition. Modern VFDs are designed to alert users to not only the exact cause of a trip condition but can record conditions leading up to the trip that may indicate entirely different causes for that eventual trip. So not only are VFDs to be more efficient, but they are designed to provide an added layer of safety for workers. This is especially important for those working in chemical, oil and gas, and mining operations, among others.

See related articles linked below on variable frequency drives.

Tom Lowery explains that VFDs designed to incorporate communication are able to achieve much higher efficiency along with process improvement by understanding in greater detail where and why power consumption varies. Evolving technologies that increase process efficiency and provide detailed information on energy use have helped, offering greater insight into the level of efficiency for their respective processes.

Figure 1: Modern VFDs allow for control and monitoring online or wirelessly with a tablet or mobile device. Courtesy: Schneider Electric

Dr. Markus Erlich explains how drive software can suppress machine vibration and the benefits of this technology include improving the cycle time and performance of machines in applications such as electronics assembly, semiconductors, machine tools, and laboratory automation. Advanced vibration suppression control used in servo drives can quickly stabilize systems that develop vibrations at a constant frequency. Proprietary control algorithms reduce the following error and the settling time of the load.

Figure 1: In applications with overhanging loads, such as gantry robots, vibration suppression eliminates the need for a massive mechanical structure. Advanced vibration suppression technology from Servotronix achieves smoother motion, faster settling tim

Sean Gaffney talks about how important it is to select the right VFD for your plant. The most important aspect, he says, is not the more current. Rather, it's the motor horsepower that is the key aspect to look into. When selecting a permanent magnet synchronous (PM) motor for an application, it is important to understand that they require VFDs to operate. PM motors, which typically have higher current values than the premium efficiency specifications, have a power factor that is very close to unity. PM motors have historically been used for specialized applications that require either very high operating speeds or high torque at lower speeds.

Vacon 100 Flow-VFD can be used for pump and fan applications. Courtesy: Vacon

Jeb Moulton explains how electromagnetic interference (EMI) and radio frequency interference (RFI) in automated machinery can negatively affect operations. Even with proper precautions, it is likely that EMI and RFI will be present in automated machinery, so components should be properly shielded. Solutions to mitigating EMI and RFI include a metal enclosure design and a proper layout that keeps power and signal components and wiring separate. Adding an EMI filter to mitigate electrical noise in automated equipment is useful, as well.

Figure 1: A spark is often produced due to high frequency switching and is a very common source of EMI in industrial applications. Image courtesy: AutomationDirect

Shady Yehia explains some of the benefits of a VFD aeration control strategy for a wastewater treatment plant. Some of the benefits include:

  • Reduction in maintenance costs, by removing the control valve, a component with a high demand on maintenance resources. 
  • Faster, more accurate and more responsive control, which often leads to reduced process variability and also ensures that the water is within the requirements of the process at all times.
  • Enhancement of the plant power factor, as VFDs contain internal capacitors that supply most of the reactive power requirements of the motors they drive. 

- Chris Vavra is production editor, Control Engineering, CFE Media,

ONLINE extra

- See the Control Engineering cyber security page.

No comments
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
This eGuide illustrates solutions, applications and benefits of machine vision systems.
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Controller programming; Safety networks; Enclosure design; Power quality; Safety integrity levels; Increasing process efficiency
Additive manufacturing benefits; HMI and sensor tips; System integrator advice; Innovations from the industry
Robotic safety, collaboration, standards; DCS migration tips; IT/OT convergence; 2017 Control Engineering Salary and Career Survey
Featured articles highlight technologies that enable the Industrial Internet of Things, IIoT-related products and strategies to get data more easily to the user.
This article collection contains several articles on how automation and controls are helping human-machine interface (HMI) hardware and software advance.
This digital report will explore several aspects of how IIoT will transform manufacturing in the coming years.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Infrastructure for natural gas expansion; Artificial lift methods; Disruptive technology and fugitive gas emissions
Mobility as the means to offshore innovation; Preventing another Deepwater Horizon; ROVs as subsea robots; SCADA and the radio spectrum
Future of oil and gas projects; Reservoir models; The importance of SCADA to oil and gas
Automation Engineer; Wood Group
System Integrator; Cross Integrated Systems Group
Jose S. Vasquez, Jr.
Fire & Life Safety Engineer; Technip USA Inc.
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
click me