4 Ways to Know if Your Cable is Right for  VFD Applications

From fans and pumps to conveyors and mixers, VFDs enable energy savings and more precise process control, while also reducing wear-and-tear on other industrial equipment. These benefits, and many others, make them one of the most useful components in discrete manufacturing and process plants.

A “real” VFD cable is designed with effective grounding to keep current within the cable, and to minimize the ground path flowing outside of the cable.

Why use VFD Cable?

If you’re thinking these benefits sound perfect for your industrial application, the next question to answer is – how do you make this happen? VFD applications present many unique challenges since they manage electrical current and other factors. Years of innovation have yielded proper cable designs for VFD applications to help ensure the VFD system operates properly.

To enjoy these advantages, you must select cabling that maximizes uptime and system reliability and is built for use in  VFD applications. Since there is no industry standard for VFD cables, it’s important to understand which characteristics are required from your cable in order to ensure reliability and protect your investment. A “real” VFD cable is designed with effective grounding to keep current within the cable and is used to minimize the ground path flowing outside of the cable. This eliminates the disturbance to surrounding equipment, networks and instrumentation. If you design your VFD system with lower-quality, or even non-VFD cable – like THHN or building wire – you can put the safety of your personnel and the reliability of your operations at risk.

You wouldn’t pick up specialized parts for a high-speed race car at your local automotive store, would you? Similarly, you shouldn’t use just any cables to build your VFD system. The products used in VFD applications need to meet an exceptionally high quality bar and be built to handle harsh environmental conditions.

When is VFD Cable required?

Here are a few of the requirements your cabling needs to meet:

• Withstands high-power signals. VFD cables carry power from AC drive systems to AC motors. This means they need to be able to continue operating fluently during high-power signals.
  
  
• Functions during extremely high voltage. The right VFD cables will help you avoid degradation or failure in the face of voltage spikes and heat build-up.
  
  
• Manages torque instantaneously. If you haven’t invested in high-quality VFD cables that protect against cable charging, you will have reduced motor torque, false motor trips and currents escaping into other systems; threatening human safety.

When using a VFD, motor speed can be changed almost instantaneously to address load and process changes, making them very useful in the industrial world.

What does VFD Cable do?

You’ve already invested in your systems’ motors and drives, so don’t skip the step of ensuring the cables are built for use specifically in VFD applications. Here are four ways to know if a cable is optimized for VFD use:

1. Built for electrical performance: High performance VFD cables are constructed with flexible (high strand count) tinned copper conductors so they can flex and bend without deteriorating the signal. This means the cables are more thermally stable at connection points, provide better corrosion and vibration resistance and have a 4-8 times increase in conductor surface area. What to ask for: High-strand, tinned copper circuit conductors
   
   
   
2. Insulated above and beyond minimum code requirements: VFD-optimized cables often significantly exceed the specified minimum wall thickness. This increases safety and performance by reducing the amount of electrical charge in the cables and enabling longer cable distances. What to ask for: Industrial VFD-grade XLPE (Cross-linked polyethylene) insulation with the proper RHHW-2 thickness
   
   
   
3. Ground and shielding protection from disruption: VFD cables should have an excess of copper in the grounding terminal. More copper will more effectively keep all electrical noise within the cable. Cables with the equivalent of three full-size phase conductors in the ground system will be most effective in containing noise. What to ask for:300 percent ground (to circuit conductor) cable design for smaller drives; 100 percent ground (to circuit conductor) cable design for larger drives
   
   
   
4. Jacketing options: VFD cables need to resist damage from physical deterioration, while remaining flexible. Cables with different options for industrial grade jacketing offer performance with the added bonus of being able to tailor a VFD cable to your specific application, depending on the level of flexibility needed. What to ask for: Do your cables face sunlight and oil exposure? Look for PVC jackets. Do you also need to protect against weld splatter and require extreme flexibility? Use TPE jackets. Do you need all of this and Halogen-free jackets? Select cable with low-smoke, zero-halogen (LSZH) jackets.
    

Using the right VFD cable ensures the benefits you expect from a VFD application. From energy savings, improved process control, reduced waste, longer motor life, reduced maintenance and higher reliability – there are a number of advantages. And as long as you use the right cables, you can realize all of these benefits.

By looking out for these four traits when specifying or purchasing cable, you can ensure you have a high-quality product that will help maximize your system’s full potential. If you want more information on VFD cabling, download the white paper available below.

Related Links

• VFD Cable 
• PDF: Unarmored Variable Frequency Drive (VFD) Cable Termination Guide
• Designnews.com blog: Engineering Directives Not Followed... Again

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