WEG's commitment to ever-higher levels of quality, performance and reliability from its electric motors is being underlined with the adoption of DuPont NOMEX for phase and slot insulation in the company's W21 line of high-efficiency motors. Insulating materials utilising a laminate of NOMEX (also known as NMN) offer a high thermal classification (220degC), high mechanical strength, outstanding electrical qualities and superior thermal resistance. These properties make the material an excellent choice for demanding motor applications where resistance to high temperatures is essential.
The adoption of NMN is in keeping with WEG's policy of always incorporating the latest technology into its manufacturing processes to produce products that conform to the highest and most demanding total quality control standards required by customers. In this case the technology objective was to develop a range of high-efficiency motors with higher thermal protection. According to Jose Reinaldo Cardoso, Material Development Analyst of WEG Industrias SA Motors Division, this is exactly what has been achieved with the adoption of NOMEX laminate insulation: "NMN supports a thermal stress three times higher than DMD, the material that we used previously. The polyester film inside the laminate ensures a high dielectric strength and NOMEX, in addition to its excellent thermal resistance, has good saturability and impregnation properties with the resin and varnishes that are used. This allows us to reduce the air voids inside the insulation material that could lead to premature failures. In addition, should the polyester component in a NMN laminate fail because of overheating, the NOMEX layers remain intact and continue to act as a physical barrier and electrical insulation material, which prevents total failure of the system. What all this means for our customers is more reliable and safer machines, especially since there is an extra margin of safety in cases where equipment is not operated correctly."
Overcoming inverter-related problems
The use of Nomex in WEG's W21 Line of high-efficiency motors is part of an overall design initiative that also includes impregnation of the motor windings with higher insulation Class 'H' varnish. The result of this combination is a state-of-the-art insulation system that withstands the voltage spikes commonly encountered with inverters. In addition, bearing protection against EDM (electrical discharge machining), which can cause motor failure, is offered as an option on W21 Line motors with frame sizes of 225 and above.