HELUKABEL recently announced that select TOPFLEX and TOPSERV VFD cable products have upgraded their conductor insulation material to XLPE from PVC/nylon to stay ahead of the curve as the industry transitions towards an electrical installation code update that requires the use of RHH, RHW, RHW-2, XHH, XHHW and XHHW-2 insulation. The product-specific cable types being upgraded are: TOPFLEX 600 VFD, TOPFLEX 650 VFD, TOPFLEX 1000 VFD, TOPSERV 600 VFD and TOPSERV 650 VFD.
There has been a change to Chapter 4, Article 126.96.36.199 – Circuits Supplied from Power Conversion Equipment that states, “Electrical conductors and equipment supplied by power conversion equipment as part of adjustable speed drive systems and servo drive systems shall be listed flexible motor supply cable marked type RHH, RHW, RHW-2, XHH, XHHW, or XHHW-2 or selected based on equipment manufacturer’s instruction.”
To date, no motor manufacturers have specifically required XLPE insulation for general VFD wiring applications. The general interpretation of the current 2018 NFPA for wiring with regards to Chapter 4, Article 188.8.131.52 is that cables using these insulation types are intended for use inside the panel where the wiring is contained between the drives and protection equipment (of the panels) that may experience unusual overload and/or a fault condition. The reason behind this belief is because this requirement is not included in Chapter 12 – Conductors, Cables and Flexible Cords, where THHN and TFFN insulation are still approved.
However, HELUKABEL does believe that the requirement for thermoset (common to RHH, RHW, RHW-2, XHH, XHHW and XHHW-2) conductors in VFDs under Chapter 12, which applies to cables used for external wiring, or outside of the control panel, will be in the next NFPA update (three to four from now). This potential code change would be the result of a shift in the market rather than a safety concern when comparing the benefits of thermoset over thermoplastic insulation in terms of premature insulation failure. This is because electrical systems are safeguarded by properly sized cables (using 125% FLA), and/or the system’s circuit protection device (circuit breaker or fuses) that would trip or blow before any conductors would be exposed to such extreme currents as to degrade the insulation.
Additionally, HELUKABEL is upgrading to XLPE insulation because it does offer electrical and mechanical performance benefits in terms of lower capacitance ratings, especially in applications that require long cable runs, (as opposed to other insulation options) to better match the motor’s impedance for helping to reduce electrical issues in the system that can waste energy and increase electrical noise. A higher current load rating is also possible due to the conductor temperature resistance of 105°C.
HELUKABEL USA Inc.