A Thermal Model for Electromagnetic Actuators

The objective of this paper is to derive an accurate lumped parameter thermal model for electromagnetic actuators (EMA) that is suitable for control purposes. This model estimates the change in coil resistance due to temperature rise when energized by constant a current pulse. The dynamic equations are developed from basic thermodynamic and heat transfer principles, namely, the first law of thermodynamics, “The Law of conservation of energy” [4]. The dynamic equations are developed from the idealization of a control volume, and formulating the first law of thermodynamics on a rate basis. The resulting differential equation is based on energy generation, energy storage and energy dissipated by the coil. The result is a control-oriented model with an estimate of coil temperature and resistance change with current input. This formulation can easily be implemented without knowing the electric drive circuit and can be used as a modeling and design tool for any solenoidal actuator.