Improved Thermal Behavior of an Electromagnetic Linear Actuator with Different Winding Types and the Influence on the Complex Impedance

Using the example of an existing linear actuator, the advantages and disadvantages of a winding body made of aluminum with aluminum oxide as insulation in comparison to a winding body made of coated copper wire are investigated. The increase in the maximum current load (increased force effect) is achieved by an improved thermal heat dissipation of the resistive losses. If the force effect is to be maintained, the increase of the current can reduce the number of windings and thus also the material and installation space. Although the coil made of aluminum is subject to higher losses due to the lower electrical conductivity of aluminum compared to copper, these losses can be better dissipated from the actuator due to the thermal conductivity of the oxide layer. The thermal conductivity of the oxide layer is about 140 times higher compared to epoxy insulation that a significant reduction in the hot spot temperature is achieved. At the same time, the winding body can be subjected to significantly higher temperatures, which enables a further reduction in installation space. In addition, the low layer thickness of aluminum oxide allows a higher filling factor (more compact design). Together with the 3 times higher permittivity of aluminum oxide compared to epoxy, this has significant effect on the effective capacities as well as the resistance and thus on electric behavior. This is the second focus of the work. The influence of the different coil concepts on the complex impedance is analyzed. Therefore analytical calculations are combined with detailed axial symmetrical FEM simulations.