Reliable Class F Motor Insulation

Class F Motor Insulation - DuPont™ Nomex® Insulation

FMV (Francaise de Motoventilateurs), the French designer and manufacturer of industrial ventilators, replaced the traditional 3-ply DMD insulation it had been using in its asynchronous motors with a 2-ply laminate of DuPont™ Nomex® brand paper and polyester film, known as laminate type NM.  FMV made the decision to upgrade to a Class F motor insulation system of Nomex® based laminate type NM after conducting extensive laboratory testing and confirming the performance data with endurance tests that simulated extreme operating conditions.

Application Description

Designed for use in particularly challenging environments, the 20 W and 5 kW ventilator motors manufactured by FMV are used in hot air production; refrigeration; air treatment; cooling of industrial equipment; and the ventilation of industrial and agricultural installations. 


These Class F motors operate at internal temperatures of 150°C, peaking at 180°C, and are subjected to demanding operating cycles that often consist of up to 100 start-ups per hour. 

Following an extensive evaluation of dielectric performance and aging, FMV decided to use Nomex® based laminate type NM as the Class F motor insulation system for its ventilator motors.  Now, FMV uses Nomex® based laminate type NM to insulate the bottom of the slots found in the asynchronous motors that are used in the company’s entire range of industrial ventilators.

Benefits Gained

Enhanced reliability:   FMV was able to achieve a reliability rate of more than 99% after adopting the use of Class F motor insulation systems of Nomex® based laminate type NM for its industrial ventilator motors.

Longer service life:   The average life span of FMV’s industrial ventilator motors more than doubled—increasing from 1,240 hours to 2,680 hours—as a direct result of switching to Nomex® based laminate type NM.

Increased productivity with fewer rejects:   The reduced thickness of the Nomex® insulation—0.18 mm (7 mils) vs. 0.25 mm (10 mils) for DMD—combined with the flexibility and smoothness of Nomex®, facilitates the automatic threading of the machines, thus making the enamel less susceptible to damage.  This makes the process faster and has reduced electrical failures during production, as well as end-of-the-line rejects, by greater than 50%.

Materials Selected and Why

Nomex® paper performed exceptionally well in the extensive tests that FMV conducted, proving that this advanced insulation material in a 2-ply NM laminate structure could help deliver the increased reliability and longer service life that FMV wanted to achieve. 

During laboratory testing, Nomex® paper was subjected to a continuous oven temperature of 180°C for 96 hours at 3,100 volts (CEI 626) without it showing the slightest dielectric or mechanical default.  Subsequent testing over a period of 500 hours still gave no sign of a breakdown. 

This performance data was confirmed during endurance tests that simulated extreme operating conditions, such as when the motor’s internal temperature rose to 240°C—due to an obstructed rotor blade—while operating at 300 start-ups per hour.


Innovative design flexibility:   According to Christian Perrot, quality manager at FMV, “We have also gained a certain innovative flexibility when it comes to the conception of new products, like more compact products, or products with variable speeds.  A new opportunity to expand our product range further and to respond better to market needs.”


Competitive advantage:   According to Perrot, “For FMV, this evolution in insulation technology of our motors constitutes a major leap forward, not only in terms of reliability but also in terms of competition.  Thanks to these technological advantages, to the increased productivity and to cost reductions in the industry afforded by adopting 2-ply Nomex®/polyester, we are now able to offer our customers, at lower prices, equipment with quasi total reliability and with a doubled service life span.”

NM is a laminate made with Nomex® brand papers and is available from an authorized laminator of Nomex®. Authorized Distributors of Laminates made with Nomex® paper.

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