Modeling and Simulation of Power Loss in Drive Unit of Electromechanical Actuator 2012-01-2232

In all-electric aircraft, electromechanical actuators (EMAs) will be used to replace hydraulic actuators. Due to the highly transient mission profiles of the aircraft operation, thermal management of EMAs is a significant issue. In this paper, we study the heat problem of the control and drive units of EMAs, and build a model to calculate and simulate the power loss and heat generation in the driver board.

The driver unit consists of a power inverter, a capacitor, a power dissipating resistor and a control circuit. The power loss of each component is studied. The heat loss in the power inverter comes mainly from the power switches: IGBTs. The on-state loss is proportional to the current of the motor, and the switching loss is determined by the switching frequency as well as current. The power loss in the power dissipating resistor is determined by the regenerative power, the capacitor and the control algorithm to stabilize the bus voltage, which varies from different mission profiles and different applications. All those parameters can be obtained in our simulation code. The power loss on the control circuit is negligible compared with the power loss on IGBTs and the power dissipating resistor, and generates very little heat in the system.

A physical model is developed to estimate the heat loss on the motor driver unit, and a simulation model is built in Simulink software. Stator currents and voltages are input variables to the code. The power losses on the power inverter and unloading resistor are calculated, as is the total power loss.

Experimental data from a 325 seconds long mission profile test is used to verify the model. Power input (current and voltage) to the electric motor is measured and used as input to our model. The power losses in the driver unit is calculated and used to estimate the temperature field of the electronic unit. The temperature results are compared with those measured by the thermocouples embedded in the driver unit.