By Eileen Harvey
Variable frequency drives (VFDs) have become indispensable components in modern industrial automation, thanks to their ability to precisely control motor speeds, enhance energy efficiency and improve overall operational effectiveness. By adjusting the frequency and voltage supplied to electric motors, VFDs enable smoother starts and stops, reduce mechanical stress and facilitate significant energy savings, particularly in applications that require variable loads.
This unwanted noise can interfere with the operation of sensitive equipment, disrupt communication signals and potentially lead to equipment damage if not properly managed. As industries continue to adopt VFD technology, understanding the implications of this electrical noise becomes increasingly important for maintaining system integrity and performance. Nonetheless, it is essential to evaluate each situation carefully to determine the most appropriate cabling solution, balancing cost considerations with the need for reliability and performance in the automation system.
What Is Shielding in VFD Cables?
Shielding is a crucial technique employed in the design of cables and electronic devices to minimize the impact of electromagnetic interference (EMI) and radio frequency interference (RFI). This interference can arise from a multitude of sources, including nearby electrical equipment, radio transmitters or even natural phenomena. To combat this issue, shielding involves the application of conductive barriers, which are typically crafted from materials such as metallic foil or braided wire.
Let’s look at the three main types of shielding. Foil shields are lightweight, affordable and effective against high-frequency noise. Braided shields are stronger and flexible and provide low-resistance paths for noise currents. Combination shields are the best of both worlds—excellent high- and low-frequency protection.
In VFD systems, shielding helps reduce electromagnetic disturbances caused by fast switching pulses traveling from the drive to the motor. Without shielding, interference can affect nearby control and communication cables, sensitive sensors and PLCs, and wireless networks or communication systems.
Why Shielding Matters in VFD Applications
Shielding in VFD cables is a necessity in many installations. VFDs generate harmonics and electrical noise, and shielding helps prevent this noise from escaping and interfering with nearby systems. Many industries such as automotive, aerospace and manufacturing require adherence to Electromagnetic Compatibility standards, and shielded cables are often needed to meet these requirements. Effective shielding also protects overall system performance since uncontrolled EMI can lead to motor overheating, erratic PLC operation or communication errors within automation networks. By limiting electrical noise, shielding reduces stress on components, extends equipment life and helps prevent costly downtime.
When Is Shielding Absolutely Necessary?
Not every VFD application requires shielding, but several scenarios make it highly advisable. High power drives above 10 HP generate greater electrical noise, making shielding critical. Long cable runs exceeding 50 feet behave like antennas and radiate interference more easily. Harsh electrical environments such as facilities with welding machines, high-voltage systems or dense automation equipment also benefit from shielded cables. Shielding is equally important when sensitive communication, data or instrumentation cables are nearby, and in industries that enforce strict EMC guidelines requiring shielded VFD cable designs.
Situations Where Unshielded VFD Cables May Work
Variable Frequency Drives are essential in modern industrial automation because they provide precise control over motor speed and torque. Although unshielded VFD cables often raise concerns about EMI and its potential impact on equipment performance, there are specific conditions where these cables can still operate effectively and present a practical solution. Shielding is generally preferred, yet unshielded cables may be sufficient in low power drive systems below 5 HP, where smaller drives generate less interference. They can also be appropriate for short cable runs under 20 feet because limited length reduces EMI radiation. Unshielded cables may work in non-critical environments where the system is isolated from sensitive equipment, and they offer a cost advantage in budget-conscious applications where shielded cables may not be necessary for acceptable performance.
Best Practices for Selecting Shielded vs. Unshielded VFD Cables
When deciding between shielded and unshielded, consider the following factors:
- Drive Size – Larger VFDs almost always need shielding.
- Motor Distance – The longer the cable, the more important shielding becomes.
- Environment – Electrically noisy environments demand shielding.
- Compliance – If your application requires EMC compliance, shielding is non-negotiable.
- Manufacturer Guidance – Always follow the VFD and motor manufacturer’s recommendations.
For industrial grade shielded VFD cables, TKD Kabel’s Kaweflex® series is a reliable choice.
Tips for Proper Installation of Shielded VFD Cables
- Ground the Shield Properly: Always connect shields at both ends for maximum EMI suppression.
- Avoid Parallel Routing: Don’t run VFD cables alongside sensitive communication cables.
- Use Metallic Conduits: Extra layer of protection for harsh environments.
- Maintain Shield Integrity: Avoid over-stripping or damaging the shield during termination.
- Regular Inspection: Periodically check shield connections and cable integrity.
Shielding ensures compliance with EMC standards, prevents costly downtime and keeps your systems running reliably. While unshielded cables may work in small, low-power or isolated setups, shielding is the safest choice for most industrial environments.
For top-tier shielded VFD cables, trust TKD Kabel Industrial-Grade Cables. With EMC-optimized designs, durability and reliability, they’re built to handle today’s demanding industrial applications.
Explore the full range of TKD Kabel through L-com. We’ll fill your orders fast, with same-day shipping on all qualified, in stock, online orders received Monday through Friday before 5 p.m. EST. For TKD-related inquiries, connect with our U.S-based TKD expert Eileen Harvey at eharvey@infiniteelectronics.com.
