Variable frequency drives (VFDs) have become very common in the industrial space and can improve your operations tremendously. However, they come with occasional challenges and potential downsides that can affect applications.

VFD Basics

VFDs control the rotational speed of alternating current electric motors by adjusting the frequency and voltage applied. Basically, this is done by switching IGBT output devices. For example, fan, pump, and air compressor applications use VFDs and account for more than half of the electricity consumed by U.S. industrial operations.

Although equipment can generally operate at less-than-maximum velocities of their connected motors without VFDs, this isn’t possible without using throttling devices such as valves, dampers, or bypasses. Therefore, a VFD provides an efficient way to control varying flow rates and pressures.

Pros of Using VFDs

• They provide substantial energy savings.
• Speed control replaces a valve or damper-type flow control.
• Smooth starting and stopping mechanisms reduce mechanical wear on loads.
• Integrated features allow for easy implementation of future modifications.
• They allow for increased power factors.
• They have regenerative braking.
• They control speeds up to 100 Hz.

Cons of Using VFDs

• There are higher initial capital costs.
• Use inverter duty motors with VFDs to optimize motor life.
• Install VFDs properly, or Harmonics may occur.
• VFDs require additional heat dissipation.

Alternatives to VFDs

If you don’t think a VFD is the right choice for your application, some alternatives may be better suited for your environment. For example, across-the-line starting does not control speed and allows for full-torque starting and stopping. Additionally, soft starting methods do not control speed but allow for smooth starting and stopping.

Learn more by contacting a Motion Automation Intelligence Specialist today.