Benefits of Epoxy There is tremendous value in epoxying the wound stators in brushless motors under extreme conditions. Due to torque and vibration created by the alternating current during operation, brushless motor stator coils are subjected to very high mechanical forces under typical racing conditions. Picture it as a super-fast and very forceful tug-of-war between the coils and the magnets. This constant pulling and pushing of current through the coils causes the coils to move in sync with the drive frequency. This force increases as the load on the motor increases. Dipping the stator in epoxy provides the windings with an additional degree of mechanical strength, particularly in the unsupported end wind. The coils are also strengthened where they enter the slot of the stator, in order to resist the tug-of-war forces caused by the torque reaction. In other words, the epoxy coating prevents coil movement caused by the changing magnetic fields created during motor operation. It is ideal to prevent the stator wires from rubbing against each other, because this vibration can eventually wear out the insulation coating, causing a short in the coil and motor failure. Thermal Benefits Another advantage of an epoxy-dipped stator is that it also displaces air (which is a barrier to cooling) from inside the coil, and replaces it with resin. This is superior because it improves the thermal conductivity of heat from the inside of the windings, to the lamination on the outside of the windings. And since the laminations are on the outside, they also help to dissipate heat into the ambient air. Epoxy dipping the stator will help it to transfer heat and perform better. In fact, an epoxy-dipped stator is 7.8 times better in heat conductivity than air, and one dipped in epoxy with thermal additives makes it a whopping 73 times better (Novak is currently researching this option). Thermal Conductivity (W/m °C)*:
*(1W/m °C = 0.5779 Btu/(ft-hr °F) Additional Benefits Finally, having a Novak epoxy-dipped stator will provide a degree of environmental protection against moisture, as well as improving the electrical insulation between the winding and the stator. Clearly the advantages of having an epoxy-dipped stator are many: It reduces damaging vibration in the coils, adds strength to the end winds, helps to keep the motor cooler, provides protection against moisture and improves the electrical insulation. Driving your vehicle with a Novak Epoxy-Dipped Stator should help your motor’s reliability and lead to many more laps around the track.
