VFD Cable Selection

Customer Q&A:
VFD CABLE SELECTION

 

Importance of Specifying the Right Cable System for VFD Applications

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OUR SOLUTION      FOLLOW-UP QUESTION

 

 

HOW TO SELECT VFD CABLE

To avoid issues commonly associated with VFD applications, it is important to specify an electrically balanced, copper tape shielded cable with XLPE insulation. This design will:

  • Reduce EMI
  • Provide a low impedance return path
  • Reliably withstand high voltage spikes
     

The ServiceDRIVE® VFD Cable System is the only off-the-shelf complete solution. The cable is made of thermoset insulation, and the conductor and ground configuration with overall copper tape shield provides the best low impedance return path.

 

 

 

WHY SPECIFICATION MATTERS

The increased adoption of variable frequency drives (VFDs) over the past decade has elevated the need for specifically engineered wire and cable solutions that ensure long-term performance. To avoid costly downtime, diagnosis, and repair of these critical operations, it is important to specify cable and termination systems designed to address motor bearing failure, cable failure, stray current, and electromagnetic interference (EMI).

However, there is some confusion in the market when it comes to specifying the right cable system and termination method that can optimize performance and improve longevity of motors utilitzing VFDs. 

 

IMPORTANCE OF CABLE CONSTRUCTION

The higher switching speeds of VFDs inherently generate more EMI that inevitably gets radiated into the environment by the inverter-to-motor power cable. The EMI emitted from the power cable can induce voltages, crosstalk, or common-mode currents onto adjacent cables and equipment, causing damage to control systems and mechanical parts.

To avoid these issues, it is important to choose an electrically balanced, shielded cable with NFPA 79 compliant crosslinked polyethylene (XLPE) insulation when specifying cable systems for VFD applications. For the best performance, a RHW-2 2kV rated cable design has superior dielectric properties to resist voltage spikes that are generated during operating conditions. Increased insulation thickness results in less impedance mismatch to the system and fewer issues with reflective wave phenomenon.

 

LESS EFFECTIVE CABLE CONSTRUCTIONS COMMONLY USED FOR VFD APPLICATIONS

  PROBLEM SOLUTION
Single and Multiconductor Thermoplastic Insulated Cables

Unshielded tray cable or single conductor cables in conduit with thermoplastic insulation (like THHN/THWN or TW90) have often been used in VFD applications. However, thermoplastic insulation cannot withstand the voltage spikes associated with VFDs. These spikes result in hotspots and pinholes in the insulation and arcing across wires or grounded surfaces.

High-quality thermoset insulated shielded cables are critical for VFD applications because of the higher dielectric strength, impedance characteristics, and physical properties. Copper tape shielding provides a smooth surface with a low impedance path for the high frequency noise or common mode stray currents.

Continuously Welded Aluminum Armor

Shielded cables are critical for VFD applications because the alternative current tends to flow on the outer surface of the conductor (called "skin effect"), resulting in an increase in the effective resistance of the conductor and stray current (if not properly terminated). Continuously welded armor cables rely on aluminum armor for the shield path, and braided shielded cables use an aluminum-backed mylar wrap and small tinned copper strands over the cable core to direct the current. 

However, given its much higher conductivity and reduced resistance, a 5-mil flat copper tape shield with 50% overlap and proper termination can better direct high frequency away from the grounding plane and provide the lowest impedance path, avoiding damage to motor bearings and sensitive electronics.

Braided Tray Cable

Braided tray cables present additional issues that adversely impact performance in VFD applications. Because the braid can only offer a percentage of total coverage and braid strands move when the cable is installed with bends, these gaps allow EMI to radiate, compounding the risk to the motor and surrounding equipment.

By contrast, a copper tape shield with 50% overlap is more flexible and can be bent around corners during installation and maintain full electrical containment.

 

White Quotations Service Wire is always ahead of the curve on new technology. Best VFD cable solution on the market.

 

White Quotations Service Wire sets the standard. You've always been resonsive to RFQs and knowledgable about wire and cable products.

VFD CABLE SYSTEM

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The ServiceDRIVE® VFD Cable System is the only complete solution proven by independent lab and field-testing to resolve issues commonly associated with VFD applications. The system consists of insulated cable with three NFPA 79 compliant XLPE conductors and three balanced grounds, 5-mil copper tape shield, and matching self-terminating connectors and termination kits.
 

  • 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.
     

By selecting the right cable system and termination method during installation, manufacturers can protect their investment and ensure peak performance of critical operations avoiding costly downtime, diagnosis, and repair.

Chart illustrating ServiceDrive's performance in "Evaluation of Motor Power Cables for PWM AD Drives"

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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

VFD Termination Kit for ServiceDrive Cable

SERVICEDRIVE®

VFD Termination Kit

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

AVAILABLE:
#14 AWG - 1000 Kcmil

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