(cary, nc – october 2013)  technology developed by lord corporation – a leading supplier of thermal management,  potting and encapsulation materials to the electronics, led and solar industries – was recently cited as a solution for improving electric motor performance in a third-party study.

the research, conducted by shafigh nategh while a graduate student at kth in stockholm, sweden, dealt with thermal management aspects of electric machinery used in high-performance applications with particular focus put on electric motors designed for hybrid electric vehicle applications. nategh’s research is titled “thermal analysis and management of high-performance electrical machines.” 

according to dan barber, ph.d., a staff scientist in lord corporation’s open technology innovation group, lord thermoset sc-320 thermally conductive potting material – a relatively soft, high thermal conductivity material (3.2 w/m-k) with sufficiently low viscosity to be used in vacuum potting — was evaluated in nategh’s research.

“nategh’s research has shown that hot spot temperatures can be reduced by 35-50 percent using this material as compared to an un-potted motor, compared to improvements of only 20-30 percent using typical epoxy potting materials,” said barber. “this material may provide significant improvements in power density of electric motors.” 

barber noted the decrease in hot-spot temperature, depending on current, may provide:

• increase in achievable power/torque for a given motor size.
• decrease in motor size for a required power/torque.
• longer operation of motor before reaching temperature limit.

according to jim greig, global sales and marketing manager, electronic materials, thermoset sc-320 was developed in response to market needs for high thermal conductivity silicones with low viscosity. he noted this research validates the applicability of the material to meet industry trends.

specially designed for thermal conductivity for electrical/electronic encapsulating applications, thermoset sc-320 is a two-component system designed to retain desirable properties associated with silicones. it exhibits low shrinkage and stress on components as it cures, and maintains a low viscosity for ease of component encapsulation compared to other highly thermal conductive materials. environmentally resistant and ul-rated to ul94v0 and 180c rti, thermoset sc-320 is composed of an addition-curing polydimethyl siloxane polymer that will not depolymerize when heated in confined spaces.

possible applications for sc-320 include those in which higher power at lighter weight is needed, such as motors for electric vehicles; aerospace actuators and motors; and portable power generation equipment. better thermal management in electric motors can reduce the current, and therefore the energy, required to provide the necessary power. it also can allow for longer motor lifetime. cost savings because of the reduced amount of copper wire required for the motor windings may also be possible. thus, savings in weight, energy, and/or cost may all be possible depending on the application.

in the first part of nategh’s thesis, new thermal models of liquid-cooled (water and oil) electric machines (i.e., motors) were proposed based on a combination of lumped parameter (lp) and numerical methods. a permanent-magnet assisted synchronous reluctance machine (pmasrm) equipped with a housing water jacket, as well as an oil-cooled induction motor where the oil was in direct contact with the stator laminations, were evaluated. in the second part of this thesis, the thermal impact of using different winding impregnation and steel lamination materials was evaluated. conventional varnish, epoxy as well as a silicone-based thermally conductive impregnation material (lord sc-320) were investigated and the resulting temperature distributions in three small induction motors were compared. the thermal impact of using different steel lamination materials was reviewed by simulations using the developed thermal model of the water cooled pmasrm. the differences in alloy contents and steel lamination thickness were studied and a comparison between the produced iron losses and the resulting hot-spot temperatures was outlined.

in comparing the effects of various impregnation materials, the hot spot temperatures of the windings were evaluated under various coolant flow rates and current levels for each of the potted motors. the hot spot temperatures of the motor impregnated with lord sc-320 were generally 40-45-degrees-c cooler than the varnish-only motor and about 12-15-degrees-c cooler than the epoxy-potted motor. no difficulties in vacuum filling were noted with lord sc-320 despite its viscosity being somewhat higher than those of the epoxy and varnish. in addition, lord thermoset sc-320 was effective at decreasing the hot spot temperatures even when the potting was not 100 percent dense. for example, the hot-spot temperature of motors potted with lord sc-320 increased by only 3-degrees-c as the potting density was decreased from 80 percent to 50 percent, whereas the hot spot temperatures of epoxy- and varnish-potted motors increased by 19-degrees-c and 25-degrees-c, respectively, as their potting densities were lowered from 80 percent to 50 percent.

lord has an extensive line of electronic and potting materials, including epoxy, urethane, silicone, and acrylic chemistries with a wide variety of mechanical properties. more details on lord potting materials can be found at http://www.lord.com/products-and-solutions/electronic-materials/potting-and-encapsulation.xml. additional information can be obtained by contacting lord corporation at [email protected] or at +1 877 ask lord (275 5673).

about lord corporation:

lord corporation is a diversified technology and manufacturing company developing highly reliable adhesives, coatings, motion management devices, and sensing technologies that significantly reduce risk and improve product performance. for nearly 90 years, lord has worked in collaboration with our customers to provide innovative aerospace, defense, automotive and industrial solutions. with world headquarters in cary, n.c. and 2012 revenues in excess of $860 million, lord has more than 2,900 employees in 25 countries and operates 15 manufacturing facilities and nine r&d centers worldwide. lord actively promotes stem education and many other community engagement initiatives where we work and live. for more information, visit http://www.lord.com.