VFD Applications - automotive manufacturing; oil, gas or petrochemical refineries; automation

Customer Q&A:
NFPA 79 COMPLIANCE

 

NFPA 79 Requirements: Are Your VFD Cables Compliant?

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HOW TO ENSURE COMPLIANCE

When specifying your cable systems for VFD applications, keep the following NFPA 97 requirements in mind:


Avoid Thermoplastic Wires
(THW, THW-2, THHN, THWN, THWN-2, UF)


Specify Thermoset Wires
(Printed RHW-2, XHHW, XHHW-2)


Require Tray Rated Products Listed to UL 1277/2277
(Type TC, CT Rated Jacketed Cables)


Ensure Cable System Includes:

  • Multiple Grounds
  • Proper Shielding
  • Proper Shield Termination

 

NEED FOR STANDARD SPECIFICATION

The increase in variable frequency drives (VFDs) over the past decade has resulted in the need for specifically engineered wire and cable solutions to achieve long-term performance and operation.

Many industry groups, standards, and specifications exist to advise VFD cable system designs and use. One important tool used is NFPA 79: Electrical Standard for Industrial Machinery, which is part of the standards portfolio of the National Fire Protection Agency (NFPA). The latest version of NFPA 79 establishes very specific wire and cable requirements for VFD applications, accumulating decades of industry experience into a design document.

 

NFPA 79 RECOMMENDED INSULATION

NFPA 79 now discourages the use of thermoplastic insulations (THW, THWN-2) and encourages the use of thermoset insulations (XHHW-2, RHW-2). Read more about the differences between thermoplastic and thermoset insulation.

Thermoplastics exhibit a higher dielectric constant and a lower resistance to corona inception voltage. High dielectric constant results in higher cable capacitance and higher charging currents, which can be electrically demanding to the insulation over time. Lower resistance to corona inception can lead to premature dielectric breakdown, which results in cable failure.

In addition to these issues, thermoplastic insulations do not perform well in DC applications or in applications such as VFDs that mimic the function of a DC circuit. Also, thermoplastic insulations can deform and melt when exposed to excessive temperatures, such as those that occur electrically when standing voltage waves exist within a VFD cable circuit.

 

FLEXIBLE MOTOR SUPPLY CABLE

NFPA 79 now specifies flexible motor supply cable, referring to the stringent requirements of UL 1277 (Power and Control Tray Cable) as well as UL 2277 (Outline of Investigation for Flexible Motor Supply Cable and Wind Turbine Tray Cable), not to be confused with flexible motor lead wire or hook-up wire.

The combination of demanding requirements of UL 44 (Rubber Insulated Wire) and UL 1277/2277 results in a VFD cable of outstanding performance if the proper cable design/system design is also used. Shielded cables, multiple grounds, tight construction geometry tolerance, and termination methods are all critical to long-term viability and performance of the VFD circuit.

 

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ALWAYS COMPLIANT

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ServiceDrive® variable frequency drive cable designs have always met the new 2018 NFPA 79 cable requirements. The complete system includes proper overall cable design and shield termination methodology to ensure long-term viability of VFD circuit requirements.

  • The heavy-duty flat copper tape shield is helically applied over the cable core with 50% overlap, ensuring full electrical containment of EMI emissions at all points even when the cable is bent.
     
  • The conductor and ground configuration and overall copper tape shield provide the best low impedance return path for stray currents.
     
  • The thermoset insulation is engineered to withstand voltage spikes, hotspots, and pinholes, preventing premature cable failure.

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RHW-2/PVC VFD Tray Cable

SERVICEDRIVE®

VFD Tray Cable

  • RHW-2/PVC, Shielded
    2,000 Volt Copper

AVAILABLE:
#14 AWG - 1000 Kcmil
PVC, ServiceCPE®, or EnviroPLUS® Jacket

XHHW-2/PVC VFD Jacketed MC Cable

SERVICEDRIVE®

VFD Jacketed MC Cable

  • XHHW-2/PVC
    600 Volt Copper

AVAILABLE:
#14 AWG - 1000 Kcmil
PVC, ServiceCPE®, or EnviroPLUS® Jacket

Direct Wiring VFD Terminating Connector

SERVICEDRIVE®

VFD Terminating Connector

  • Direct Wiring (Tray)
    2,000 Volt Copper

AVAILABLE:
#14 AWG - 750 Kcmil

Liquidtight VFD Terminating Connector

SERVICEDRIVE®

VFD Terminating Connector

  • Liquidtight (Tray)
    2,000 Volt Copper

AVAILABLE:
#14 AWG - 750 Kcmil

NPT Conduit VFD Terminating Connector

SERVICEDRIVE®

VFD Terminating Connector

  • NPT Conduit (Tray)
    2,000 Volt Copper

AVAILABLE:
#14 AWG - 750 Kcmil

Jacketed MC VFD Terminating Connector

SERVICEDRIVE®

VFD Terminating Connector

  • Jacketed MC
    600 Volt Copper

AVAILABLE:
#14 AWG - 750 Kcmil

ServiceDrive Termination Kit

SERVICEDRIVE®

VFD Termination Kit

  • Tray or MC Cable
    600/1,000/2,000 Volt Copper

AVAILABLE:
#14 AWG - 1000 Kcmil

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Our ISO 9001:2015 certification is proof that we are focused on updating our quality systems to meet and exceed industry standards. Learn the differences between ISO 9001:2008 and ISO 9001:2015 on our Customer Q&A.

 

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THHN vs. XHHW-2: What's the Difference?


Thermoset XLPE insulation is superior to the thinner PVC insulation used in thermoplastic products (like THHN/THWN-2). Learn more about the differences between THHN and XHHW-2.

 

 

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