Form-Stable Composite Phase Change Material Based Cooling of Small Brushless DC Motor Windings

This work aimed to develop form-stable composite phase-change materials for use as a cooling system in the winding of small brushless dc motors. Halloysite, a type of porous material, was used to encapsulate the phase-change material paraffin wax. The phase transition enthalpy and thermal stability of the halloysite/paraffin composite phase-change materials were determined using differential scanning calorimetry (DSC) and thermogravimetric analyses (TGA). Subsequently, the sample underwent 50 heating–cooling cycles to assess its material quality and reliability. An optimal ratio of halloysite to paraffin, based on their thermal properties, was determined. Additionally, to enhance heat conductivity, a specific amount of tetrapod-like zinc oxide whiskers (T-ZnOw) and boron nitride (BN) was added. The molten hybrid phase-change material was applied to the winding, allowed to cool naturally, and then electrified to the stator winding. The temperature of the winding was measured using a thermistor, and the stator surface temperature was captured by an infrared thermal imaging camera. The addition of BN as a filler improved the thermal conductivity of the composite by 39.15%, ensuring high latent heat and no leakage of the paraffin wax. Under the condition of twice the rated current of the motor, the composite material significantly enhanced the motor’s cooling effect and extended the duration of overload operation by a factor of two under the same temperature constraints. This innovative approach effectively prevented leakage and overheating of the winding without modifying the original structure of the motor, leading to new ideas in the design of cooling systems for small brushless dc motors.