Forced liquid cooling of piezoelectric stack actuator utilizing silicone oil

Piezoelectric stack actuators (PESAs) are usually used in applications requiring a fast response, high resolution, and high accuracy. Self-heating during continuous drive with a large voltage amplitude at high frequencies can damage PESAs and limit the driving conditions. A sufficient cooling method is necessary to increase the driving frequency and driving amplitude. This paper proposes a direct forced liquid cooling system for PESAs and experimentally and numerically evaluates the PESA temperatures when employing this cooling system. Silicone oil, which is an excellent electrical insulator, and has a high heat transfer coefficient and good stability, was selected as the coolant. The proposed forced liquid cooling can suppress the temperature rise to about 10% of that achieved through natural heat dissipation. With an input voltage amplitude of 50 V_pk at a frequency of 10 kHz, the PESA cannot be continuously driven with natural heat dissipation. Using the proposed liquid cooling, the temperature of the PESA resin coating was kept well below the upper limit given by the manufacturer. Furthermore, the internal temperature of the PESA was estimated from heat transfer analysis using a finite element model. This confirmed that the internal temperature of the PESA was lower than the Curie temperature.