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Sponsored by Parker Lord.
Now greater than ever, we’re seeing a powerful pattern towards the electrification of autos within the transportation trade, together with vehicles, buses, trains, off-road autos, watercraft and plane. In these electrical autos, lengthy ranges and excessive horsepower require excessive energy density from their electrical parts comparable to batteries, motors and mills, and the facility electronics wanted for operation. The pattern is concentrated on smaller, inexpensive parts that may save house and scale back prices whereas boosting energy effectivity.
A key problem in creating these parts is to handle the warmth generated by smaller, high-power units like on-board battery chargers, energy inverters and converters and electrical machines. Thermally conductive potting compounds are perfect for quickly and successfully conducting warmth away from energy parts to the warmth sink. The potting compound fills the element enclosure, leaving no air gaps. Consequently, warmth is dissipated throughout the enclosure and quickly carried out to the warmth sink, which has enabled substantial measurement and weight reductions of the completed element.
In Parker Lord’s whitepaper “Thermally Conductive Potting Compounds Allow Greater Energy Density Electronics,” they share the outcomes of a research carried out by a group of Parker Lord and Manzanita Micro consultants who examined the warmth rise of inductors potted in a liquid-cooled aluminum fixture.
Supplies used within the research
On this research, they used 5 silicone potting supplies. All of the supplies are electrically insulative with excessive dielectric energy and high-temperature stability. These silicone potting supplies embody:
- Thermoset® SC-400 Silicone Encapsulant: a transparent, comfortable gel with low thermal conductivity (0.1 W/m∙Ok) used for potting delicate electronics the place excessive dielectric energy and really low mechanical stress are desired.
- CoolTherm® SC-305, SC-309, SC-320 and SC-324 Thermally Conductive Silicone Encapsulants: Crammed silicone potting supplies with progressively greater thermal conductivities of 0.7, 1.0, 3.0, and 4.0 W/m∙Ok, respectively.
These supplies are at the moment being utilized in quite a few purposes to guard delicate digital parts from extra warmth, together with on-board chargers, inverters and electrical motor stators for EVs.
A key differentiating property of their thermally conductive silicone supplies is their low viscosity in comparison with aggressive supplies with comparable thermal conductivity. The decrease viscosity permits Parker Lord’s supplies to stream and fill voids extra readily whereas offering glorious thermal conductivity. They’re additionally simpler to degas, which means that components might be potted which can be primarily void-free if a vacuum potting course of is used.
Inductor potting and testing
The inductors used on this research have been created from Micrometals T400-61D high-temperature, magnetic-powder toroid cores wrapped with 62 turns of 10-gauge insulated copper wire, which yield about 500 μH inductance at load. Inductors have been potted in custom-made aluminum cooling plates fitted with liquid inlet and outlet ports for connection to an exterior circulating fluid bathtub. The 5 completely different supplies have been used to pot three inductors with every materials, leading to a complete of 15 potted inductors.
Earlier than potting, every inductor was fitted with a thermocouple to measure its temperature. The situation of the thermocouple corresponds to the most well liked location within the inductor as judged qualitatively from a thermal digital camera picture of an unpotted inductor beneath load.
For the thermal exams, every inductor was related to a Manzanita Micro PFC40X-188 charger passing 9.3 kW and 40 A at 240V enter with 0.98 energy issue. The ability on the inductor was 30W. The aluminum cooling plate was related to a temperature-controlled liquid bathtub; every inductor was examined at coolant temperature set factors of 25°C, and the standard automotive coolant temperature of fifty°C. A second thermocouple was hooked up to the outside of the cooling plate to observe temperature adjustments through the check; nevertheless, the temperature rise of the cooling plate was lower than 2°C, even in essentially the most excessive instances.
Throughout every thermal check, the temperatures of the inductor and cooling plate have been recorded utilizing an Omega Gentle knowledge logger. The cooling plate and inductor temperatures have been allowed to stabilize with no energy. Energy was then utilized, and the temperature was monitored till the inductor temperature stabilized. The equilibration time was chosen on the level when the temperature reached a gradual state (i.e., no additional temperature enhance came about), and the reported temperature rise was calculated as the ultimate temperature of the inductor minus the preliminary temperature.
Outcomes
Through the research, they used 5 of their silicone potting supplies and examined 15 inductors a minimum of as soon as with a number of examined a number of occasions to find out repeatability. Error bars are plus and minus one normal deviation of the info, which incorporates part-to-part variation and repeatability.
The information present that each the inductor temperature rise, and the equilibration time are unbiased of the coolant temperature, as the info at 25°C and 50°C are almost superimposable and throughout the check variation. It is very important be aware that the variation turns into a lot smaller because the thermal conductivity will increase as a result of more practical thermal connection to the aluminum cooling plate.
Evaluating an inductor potted with an insulating materials (0.1 W/m∙Ok) to essentially the most conductive materials (4.0 W/m∙Ok), the warmth rise is decreased by about 50°C, and the time required to achieve a steady temperature is decreased from almost two hours to fifteen minutes. These vital enhancements in warmth administration allow the event of considerably smaller energy electronics.
Dramatic reductions in each temperature rise and equilibration time are noticed for inductors potted with thermally conductive supplies. The typical temperature rise with Parker Lord’s Thermoset SC-400 encapsulant was about 55°C, and the common rise for the corporate’s most thermally conductive supplies, CoolTherm SC-320 and SC-324 encapsulants, was lower than 10°C. Even the reasonably conductive silicones, CoolTherm SC-305 and SC-309 encapsulants at 0.7 and 1.0 W/m∙Ok, respectively, offered vital enhancements.
Below completely different check situations that will generate a temperature rise a lot higher than 55°C, the advance would seemingly be much more pronounced. Equally, the equilibration time was additionally dramatically lowered with the upper thermally conductive supplies. With the non-conductive silicone, Thermoset SC-400 encapsulant, almost two hours was required to achieve a gradual state, whereas a steady temperature was achieved in lower than 20 minutes for CoolTherm SC-320 and SC-324 encapsulants.
This speedy temperature restoration signifies that warmth is dissipated shortly, and parts will spend much less time at elevated temperatures, thus growing the lifetime of the parts.
Conclusions
Correct thermal administration is crucial for creating energy electronics which can be smaller and lighter. And smaller and lighter means greater energy density. Because the research proves, utilizing thermal administration supplies gives the distinctive mixture of excessive thermal conductivity and low viscosity in addition to substantial reductions in each most temperature rise and the time to achieve a steady temperature. Each advantages result in enhancements in effectivity and element lifetime, thereby enabling high-performance energy electronics.
Parker Lord’s group, comprised of seasoned technical help and utility engineers, is ready to help you all through your energy digital design course of. Their huge expertise consists of working with electrical car OEMs and battery corporations on cutting-edge know-how. Nevertheless, their scope extends past batteries. They’re dedicated to making sure that energy electronics – together with inverters, converters, and e-motors – operate safely, reliably and effectively by implementing efficient thermal administration methods.
In the event you’d prefer to be taught extra about options for energy electronics, please attain out to their group.
To learn the whitepaper, “Thermally Conductive Potting Compounds Allow Greater Energy Density Electronics,” go to their web page to obtain it now.
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