Variable frequency drives (VFD’s), also known as variable-speed or adjustable-speed drives are used to power AC motors in a variety of industrial motion control, commercial  flow/pumping, and extrusion applications. Benefits of using a VFD over traditional DC drives include more precise motor control and improved power efficiency. While there are many benefits to using VFD’s, their use requires special considerations for other drive  system components; especially the drive’s output cabling.

Why Use VFD Cables?

A VFD cable will experience high voltage spikes under normal operating conditions as a result of the high-frequency switching technology used in the drive. These high voltage spikes can well exceed the voltage rating of the cable; reducing the longevity and reliability of both the cable and the overall drive system. These voltage spikes increase with cable length, making longer cable runs more prone to premature insulation failure. Additionally, these high-voltage spikes generate high levels of radiated and conducted noise, which can interfere with communications and low-voltage cables in close proximity to the VFD cable. Because of these issues, use of a cable specifically designed for VFD applications is crucial to the reliability of the drive system.

VFD Cable Types

A variety of VFD-specific cables are commercially available. These cables vary by shield type (foil/braid, copper tape, armor) and voltage level; 600V, 1KV, and 2KV.  Each voltage level directly relates to the thickness of the cable’s insulation; the higher the voltage rating, the heavier the insulation, the better the cable resists high voltage spikes.

How to Choose the Right VFD Cable?

Answering the following questions can help you to decide which VFD cable is best suited for your application.

  • Does the cable require physical protection? Will it be exposed to physical harm under normal operating conditions?
  • Is the cable being used in an application where the cable run will be >150’?
  • Will the VFD cable be run near any low-voltage or communications cables?
  • Does the cable need to be flexible or easy to install?

 

Applying the answers to the application guide below can help you in selecting the appropriate VFD cable for your application.


Construction

Physical Protection


Long Cable Runs


Noise
Immunity


Ease of Installation


Fexibility


1KV Foil/Braid

B

A  

A

A

A
2KV Copper Tape
C
A B B C
600V Copper Tape

C C B B C
600V Continuous Armor

A C B C N/R

Performance Key:

A - Superior; B - Enhanced; C- Sufficient; N/R - Not Recommended