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Lifetime of Piezoelectric Actuators (PZTs)
The lifetime of a Piezo is not limited by wear and tear. Tests have shown that PI PZTs can perform BILLIONS of cycles without loss of performance if operated under suitable conditions.Generally, as with capacitors, the lifetime of a Piezo is a function of the applied voltage. The average voltage should be kept as low as possible. This is why PI has specially designed actuators and electronics for semibipolar operation, an important advantage over conventional actuator/driver combinations.
There is no generic formula to determine the lifetime of a Piezo because of the many parameters such as temperature, humidity, voltage, acceleration, load, operating frequency, insulation materials, etc. which have an (nonlinear) influence. PI PZTs are built for maximum lifetime under actual operating conditions. We do not manufacture our Piezo ceramics with the goal of maximum displacement at the expense of longterm reliability. The operating voltage range figures in the technical data tables are based on years of experience with scientific and industrial OEM applications.
Research Paper on Piezoelectric Multilayer Actuator Lifetime
Research Paper on Piezoelectric Operation at Low Temperature
Statistics show that most failures with piezo actuators occur because mechanical installation guidelines are not observed and mechanical stress, shear forces and torque exceed the permissible limits. PI offers a variety of preloaded actuators, ball tips, flexible tips and custom designs to eliminate these critical forces. Failures can also occur when humidity and conductive materials such as metal dust degrade the Piezo's insulation strength, leading to dielectric breakdown. PI has designed hermetically sealed actuators for applications in critical environments.
Example:
The P-842.60 LVPZT (see "Piezo Actuators" section) shall operate a switch with a stroke of 100 mm. The switch shall be open for 70% and closed for 30 % of it's operating time.
Optimum solution: The switch should be designed in a way that the open position is achieved with the lowest possible operating voltage. To reach a displacement of 100 mm, a voltage amplitude of approximately 110 V is required (nominal displacement @ 100 V is only 90 mm). Since the P-842.60 can be operated with -20 V, the closed position should be assigned to 90 V, and the open position to -20 V. When the switch is not operating at all, the voltage on the Piezo should be 0 V.
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