A dynamic simulation model of magnetostrictive actuators and transducers has been used to study the performance and thermal balance of an ultrasonic magnetostrictive power transducer. Electrically resistive, eddy current, mechanically resistive and hysteresis losses have been deduced when the transducer works against a purely mechanically resistive load of r a moderate driving current of 10 A and a frequency of 21 kHz. The eddy current losses can be reduced significantly by laminating the active material. However the hysteresis losses are the main source for heating the transducers. The power losses obtained from the dynamic simulations have been used as thermal sources in electro-thermal finite element calculations. The calculations show that free air convection is not enough to cool the actuator. Water cooling of the actuator with a flow of 6.8 l/min will decrease the active materials temperature to around 80 degrees C. This has been obtained by estimating the heat transfer and use the heat flow as sinks in the finite element calculations. The design of a magnetostrictive ultrasonic transducer must therefore comprise an optimal working point regarding magnetic biasing and mechanical pre-stress to minimize the hysteresis.
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